JP2011207040A - Inkjet printer and pressure adjustment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a constant pressure of ink held in a head with a simple constitution.SOLUTION: In an inkjet printer, a pressure adjustment device 6 is installed in a supply channel which the head connects with an ink tank. The pressure adjustment device 6 is equipped with a cylinder 61, a piston 62 and a biasing part 65. In the cylinder 61, an inlet 611 is formed on the ink tank side of the supply channel while an outlet 641 is formed on the head side thereof. The inlet 611 is closed when the biasing part 65 biases the piston 62 toward one side in the axial direction of the cylinder 61. When the piston 62 moves toward the other side in the axial direction according to the reduction of ink pressure in the head caused by discharging ink, the inlet 611 is opened and the ink flows into the cylinder 61 from the inlet 611, and then the ink flows out of the outlet 641 into the head. The pressure adjustment device 6 with simple constitution keeps constant the ink pressure held in the head.

Description

  The present invention relates to a pressure adjusting device that keeps the pressure of ink held in a head constant, and an ink jet printer including the pressure adjusting device.

  2. Description of the Related Art Conventionally, an ink jet printer that performs printing on an object by scanning a head on which a plurality of ejection openings that eject minute droplets of ink are arranged along the object to be printed has been used. In an example of an ink jet printer, a container for storing ink is disposed in the vicinity of the head, and the ink level in the container is made lower than the discharge port of the head so that the ink in the container is supplied to the head due to a water head difference. (See, for example, Patent Document 1). Patent Document 1 discloses a method of installing a container at a higher position than the inkjet head by providing a fine differential pressure adjusting mechanism that generates a negative differential pressure with an electropneumatic regulator between the inkjet head and the container. Has been.

  In Patent Document 2, ink maintained in a negative pressure state in an ink jet recording head by an ink supply unit configured as a differential pressure valve including a coil spring and a movable film that is always elastically contacted with a valve seat by the coil spring. Is disclosed.

JP 2009-165951 A JP 2008-247042 A

  By the way, when the ink in the ink tank (container) is supplied to the head due to the water head difference, as described above, the ink tank is disposed in the vicinity of the head, and the ink level in the ink tank is set to the ejection port of the head. Therefore, the actual ink tank arrangement is limited to the side of the object (or its holding part) located near the discharge port of the head, and the degree of freedom in designing the ink jet printer is limited. It will be lower.

  In addition, by providing a mechanism for negative pressure in the ink tank, the ink tank can be arranged above the head, and the degree of freedom in design is increased, but the negative pressure in the ink tank is controlled to be constant. This is not easy and requires a complicated mechanism. In the unlikely event that the negative pressure in the ink tank changes significantly, the pressure of the ink held in the head also changes, affecting the ejection of ink from the ejection port and degrading the quality of the image formed. Resulting in. Therefore, there is a need for a new technique that can keep the pressure of ink held in the head constant with a simple configuration without excessively limiting the arrangement of the ink tank.

  SUMMARY An advantage of some aspects of the invention is that the pressure of ink held in a head is kept constant with a simple configuration.

  The invention according to claim 1 is an ink jet printer, wherein a head that ejects ink toward an object, a moving mechanism that moves the object relative to the head, and a supply channel are provided. An ink tank that is connected to the head and that stores ink, and a pressure that is provided in the supply flow path and that is supplied from the ink tank to the head and that keeps the pressure of the ink held in the head constant. A cylinder having an inlet provided on the ink tank side in the supply flow channel and an outlet provided on the head side, and a piston inserted into the cylinder. And a biasing portion that biases the piston toward one side in the axial direction of the cylinder and closes the inlet. As the pressure of ink in the head decreases, the piston moves to the other side in the axial direction, so that the inflow port is opened and ink flows into the cylinder from the inflow port, and the head flows from the outflow port. Ink flows out.

  A second aspect of the present invention is the ink jet printer according to the first aspect, wherein the inflow port is formed in a side portion of the cylinder, faces the side portion of the piston, and the piston is in the axial direction. And a flow path through which ink that flows into the cylinder from the inflow port flows when moved to the other side.

  Invention of Claim 3 is an inkjet printer of Claim 1 or 2, Comprising: The said urging | biasing part has an elastic member, The end surface of the said one side of the said axial direction of the said piston is a circumference | surroundings Opened.

  Invention of Claim 4 is an inkjet printer in any one of Claim 1 thru | or 3, Comprising: While the said pressure adjustment apparatus urges | biases the said piston toward the said other side of the said axial direction, Another urging unit that can adjust the urging force is further provided.

  Invention of Claim 5 is an inkjet printer in any one of Claims 1 thru | or 4, Comprising: Another head which has the structure similar to the said head, A part of said supply flow path, A manifold connected to the head and the other head, wherein the outlet of the pressure adjusting device is connected to the manifold.

  A sixth aspect of the present invention is the ink jet printer according to the fifth aspect, wherein the moving mechanism continuously moves the object in a predetermined scanning direction, and is perpendicular to the scanning direction. With respect to the arrangement direction parallel to the recording surface of the object, a plurality of ejection ports in the plurality of heads connected to the manifold are arranged over the entire recording range of the recording surface.

  A seventh aspect of the present invention is the ink jet printer according to any one of the first to sixth aspects, wherein the head, the moving mechanism, and the pressure adjusting device are accommodated, and a chamber body whose inside is depressurized is provided. Further prepare.

  The invention according to claim 8 is provided in a supply flow path that connects a head that discharges ink toward an object and an ink tank that stores ink, and is provided from the ink tank via the supply flow path. A pressure adjusting device that maintains a constant pressure of ink that is sent to a head and that is held in the head, and an inlet provided on the ink tank side in the supply flow path, and a flow provided on the head side. A cylinder having an outlet; a piston inserted into the cylinder; and a biasing portion that biases the piston toward one side in the axial direction of the cylinder and closes the inflow port. The piston moves to the other side in the axial direction as the pressure of the ink in the head decreases due to ejection, thereby opening the inlet and opening the inlet from the inlet. Ink flows into the Sunda, ink flows out into the head from the outlet port.

  A ninth aspect of the present invention is the pressure adjusting device according to the eighth aspect, wherein the inlet is formed in a side portion of the cylinder, faces the side portion of the piston, and the piston is connected to the shaft. A flow path through which ink flows into the cylinder from the inlet when moving to the other side in the direction.

  A tenth aspect of the present invention is the pressure adjusting device according to the eighth or ninth aspect, wherein the urging portion has an elastic member, and the end surface on the one side in the axial direction of the piston is the periphery. Released.

  The invention according to claim 11 is the pressure adjusting device according to any one of claims 8 to 10, wherein the piston is urged toward the other side in the axial direction, and the urging force can be adjusted. And further comprising another urging section.

  According to the present invention, the pressure of ink held in the head can be kept constant with a simple configuration.

  According to the third and tenth aspects of the present invention, it is possible to prevent the difference between the ambient pressure and the pressure of the ink in the head from changing due to a change in the ambient pressure. The pressure of the ink in the head can be easily adjusted.

  According to the fifth aspect of the present invention, the pressure adjusting device can be provided in the vicinity of the plurality of heads, and the pressure adjusting device can promptly respond to the pressure fluctuation of the ink in the head so that the pressure of the ink in the head. Can be made constant with high accuracy.

1 is a perspective view of an ink jet printer according to a first embodiment. It is a bottom view of a discharge part. It is a figure which shows the structure of a head unit and an ink supply mechanism. It is a disassembled perspective view of a pressure regulator. It is sectional drawing of a pressure regulator. It is sectional drawing of a pressure regulator. It is a figure which shows the other example of a pressure regulator. It is a figure which shows the inkjet printer which concerns on 2nd Embodiment. It is a figure which shows the other example of arrangement | positioning of a pressure regulator.

  FIG. 1 is a perspective view showing an appearance of an ink jet printer 1 according to a first embodiment of the present invention. The ink jet printer 1 is an apparatus that forms a color image on a sheet-like substrate 9 having liquid repellency such as a film.

  The ink jet printer 1 of FIG. 1 includes a main body 11 and a control unit 4, and the main body 11 transports a sheet-like base material 9 continuously moving in the Y direction (hereinafter also referred to as “scanning direction”) in FIG. 1. And a discharge unit 3 that discharges fine droplets of ink toward the main surface (the main surface on the (+ Z) side, hereinafter referred to as “recording surface”) of the base member 9 that is moving. . In the transport unit 27, a plurality of rollers 271 that are long in the X direction in FIG. 1 are arranged in the Y direction perpendicular to the X direction, and a roll-shaped substrate is disposed on the (+ Y) side of the plurality of rollers 271. 9 (supply roll) is provided, and a winding unit 273 is provided on the (−Y) side of the plurality of rollers 271 to hold the roll-shaped base material 9 (winding roll). In the following description, the term “base material 9” refers to a part in the middle of conveyance (that is, part of the base material 9 on the plurality of rollers 271).

  One roller 271a of the transport unit 27 is provided with an encoder 29 that detects the moving speed of the base material 9 in the scanning direction, and the control unit 4 controls the rotation of the motor of the winding unit 273 based on the output of the encoder 29. As a result, the substrate 9 moves in the (−Y) direction at a constant speed. Actually, by applying a load (tension) in the direction opposite to the moving direction (that is, (+ Y) direction) to the base material 9 by the motor of the supply unit 272, the bases on the plurality of rollers 271 are set. The material 9 moves smoothly without undulations.

  The discharge unit 3 is disposed above the plurality of rollers 271 (the (+ Z) side in FIG. 1), and the discharge unit 3 is fixed to the frame 25 provided on the base 20 so as to straddle the rollers 271. A light source 39 for emitting ultraviolet rays is provided on the frame 25, and a plurality of optical fibers (actually, the plurality of optical fibers are bundled. In FIG. The light from the light source 39 is introduced into the inside of the discharge section 3 through the above.

  FIG. 2 is a bottom view of the discharge unit 3. As shown in FIG. 2, the ejection unit 3 includes a plurality (four in FIG. 2) of head units 33 that eject inks of different colors, and the plurality of head units 33 are arranged in the Y direction. It is fixed to the main body 30 of the discharge part 3. The most (+ Y) side head unit 33 in FIG. 2 ejects K (black) color ink, and the (−Y) side head unit 33 of the K head unit 33 is C (cyan) color ink. The (−Y) side head unit 33 of the C head unit 33 discharges M (magenta) color ink, and the (−Y) side head unit 33 has Y (yellow) color ink. Ink is ejected. Each color ink contains an ultraviolet curing agent and has ultraviolet curing properties. The ejection unit 3 may further be provided with head units for other colors such as light cyan, light magenta, and white. The ink may be water-based ink, high viscosity ink, or the like.

  In each head unit 33, a plurality of heads 32 (for example, piezo drive type heads) having the same structure are in the X direction (direction perpendicular to the Y direction and Z direction) in FIG. 2, and are hereinafter referred to as “arrangement direction”. ), And a plurality of discharge ports (shown by dots 321 only in some of the heads 32) are arranged in the arrangement direction on the (−Z) side surface of each head 32. It is formed. As a result, in the entire head unit 33, a large number of discharge ports 321 are arranged at a constant pitch in an arrangement direction perpendicular to the scanning direction and parallel to the recording surface of the substrate 9, and the scanning direction in the scanning direction is formed on the recording surface. A plurality of dots arranged in a line in the arrangement direction can be formed at each position. Actually, with respect to the arrangement direction, the plurality of ejection ports 321 of each head unit 33 are arranged over the entire recording range of the recording surface (here, substantially over the entire width of the base material 9). Printing of the image on the base material 9 is completed only by the base material 9 passing once below the discharge unit 3 (so-called one-pass printing).

  Further, in the ejection unit 3 of FIG. 2, a light irradiation unit 38 connected to the light source 39 is provided on the (−Y) side of the plurality of head units 33. In the light irradiation unit 38, a plurality of optical fibers are arranged along the X direction, and the light irradiation unit 38 irradiates the linear region extending in the X direction on the substrate 9 with ultraviolet rays. Thus, the ink immediately after being ejected onto the recording surface is irradiated with ultraviolet rays from the light irradiation unit 38, and the ink is cured in a short time.

  In the inkjet printer 1, each head unit 33 is connected to an ink supply mechanism 5 (see FIG. 3 described later), and ink is supplied to the head unit 33 by the ink supply mechanism 5. In the following description, attention is paid to the head unit 33 and the ink supply mechanism 5 of one of a plurality of colors, but the other colors have the same configuration.

  FIG. 3 is a diagram showing the configuration of the head unit 33 and the ink supply mechanism 5. Although three heads 32 are illustrated in FIG. 3, the actual head unit 33 is provided with a number of heads 32 as shown in FIG.

  As shown in FIG. 3, the head unit 33 includes a single manifold 34, and the manifold 34 includes a substantially cylindrical manifold main body 341 disposed near the top of the plurality of heads 32, and the manifold main body 341 and a plurality of the manifold main bodies 341. A plurality of ink introduction pipes 342 are connected to the head 32 and guide the ink in the manifold body 341 to the plurality of heads 32. One end of the manifold body 341 is closed, and the other end is connected to one end of the supply line 51 via a pressure adjusting device 6 described later. The other end of the supply line 51 is connected to an ink tank 52 that stores ink. The supply line 51 is provided with a pump 53 that is a liquid feeding unit. In this way, the ink tank 52 is connected to the head 32 through the supply flow path using the supply line 51, the pressure adjusting device 6, and the manifold 34 as the supply flow path, and the ink in the ink tank 52 is sent to the head 32. In the ink jet printer 1, the positional relationship between the head 32 and the ink tank 52 is not limited, and the ink tank 52 can be arranged at an arbitrary position.

  FIG. 4 is an exploded perspective view of the pressure adjusting device 6, and FIG. 5 is a cross-sectional view of the pressure adjusting device 6 on a plane including the central axis J1. As shown in FIGS. 4 and 5, the pressure adjusting device 6 includes a cylinder 61 centered on the central axis J <b> 1, a piston 62 inserted into the cylinder 61, and first and second cover portions that close both ends of the cylinder 61. 63 and 64, and a biasing portion 65 that biases the piston 62 toward the first cover portion 63. The cylinder 61, the piston 62, and the first and second cover portions 63 and 64 are formed of a resin such as stainless steel or polyacetal.

  In the center of the second cover portion 64, a circular opening 641 centered on the central axis J1 (as will be described later, since this is an opening through which ink in the pressure adjusting device 6 flows out, hereinafter referred to as an “outlet 641”). .) Is formed, and an annular protrusion 642 that protrudes toward the piston 62 is formed around the outflow port 641. The urging portion 65 has a plurality of guide pins 651 parallel to the central axis J1, and each guide pin 651 is fixed by a fixing hole 643 provided in the annular projecting portion 642. The plurality of fixing holes 643 are formed at equal angular intervals in the circumferential direction around the central axis J1, and the plurality of guide pins 651 are disposed around the central axis J1. A plurality of holes 621 into which the plurality of guide pins 651 can enter are formed in the end surface 620 b of the piston 62 on the second cover portion 64 side, and the tips of the plurality of guide pins 651 are inserted into the plurality of holes 621.

  As shown in FIG. 5, the first cover portion 63 is also provided with one guide pin 631 parallel to the central axis J1, and the hole through which the guide pin 631 can enter the end surface 620a of the piston 62 on the first cover portion 63 side. 622 is formed. In the pressure adjusting device 6, the movement of the piston 62 in the direction of the central axis J <b> 1 is guided by the guide pins 651 and 631 inserted into the holes 621 and 622.

  The urging portion 65 further includes a plurality of springs (compression coil springs) 652 fitted into the plurality of guide pins 651, one end of the spring 652 abuts on the second cover portion 64, and the other end abuts on the piston 62. . Specifically, the fixing hole 643 of the second cover portion 64 is a so-called two-stage hole in which the diameter of the portion close to the piston 62 is larger than that of the far portion, and is formed in a portion where the diameter of the fixing hole 643 changes. One end of the spring 652 contacts the annular surface. Similarly, the hole 621 of the piston 62 is a two-stage hole in which the diameter of the portion close to the second cover portion 64 is larger than that of the far portion, and a spring is formed on the annular surface formed in the portion where the diameter of the hole 621 changes. The other end of 652 contacts. The plurality of springs 652 of the urging portion 65 urges the piston 62 toward the first cover portion 63 in the direction of the central axis J1.

  The first cover 63 is formed with a plurality of vent holes 632 (in FIG. 5, only one vent hole is provided with a reference numeral 632), and the end surface 620a of the piston 62 is opened to the surrounding atmosphere. The Therefore, when the inside of the cylinder 61 is approximately equal to the atmospheric pressure, the end surface 620 a of the piston 62 comes into contact with the first cover portion 63 by the urging force of the urging portion 65. In the pressure adjustment device 6, instead of the spring 652, another elastic member such as rubber may be used (the same applies to the spring 663 in FIG. 7 described later).

  As shown in FIGS. 4 and 5, a hole 623 serving as an ink flow path is formed on the inner side (center axis J1 side) of the plurality of holes 621 on the end surface 620b of the piston 62 on the second cover portion 64 side. The An annular groove 624 is formed on the outer peripheral surface of the substantially cylindrical piston 62 in the vicinity of the center in the direction of the central axis J1. A plurality of openings 625 are formed on the bottom surface of the annular groove 624, and the annular groove 624 is connected to the hole portion 623 through the plurality of openings 625 arranged in the circumferential direction.

  As shown in FIG. 5, an annular groove 612 is formed on the inner peripheral surface (cylindrical surface) of the cylinder 61. Further, an inlet 611 connected to the annular groove 612 is formed on the side of the cylinder 61, and the inlet 611 faces the side of the piston 62. One end of the supply line 51 in FIG. 3 is connected to the inflow port 611, and the outflow port 641 of the second cover portion 64 is connected to the manifold body 341. Thus, the inlet 611 is provided on the ink tank 52 side in the ink supply flow path, and the outlet 641 is provided on the head 32 side.

  In the ink jet printer 1, the pressure adjusting device 6, the manifold 34, and the plurality of heads 32 are filled with ink in advance, and are relatively high in the vicinity of the inflow port 611 through the supply line 51 due to the liquid feeding operation of the pump 53. Pressure ink is supplied. As shown in FIG. 5, in a state where the end surface 620 a of the piston 62 is in contact with the first cover portion 63, the annular groove 624 is positioned closer to the first cover portion 63 than the inlet 611, and the inlet 611 is the piston. It is closed by the side portion 62 (the side surface closer to the second cover portion 64 than the annular groove 624).

  During printing (image formation) by the ink jet printer 1, the ink amount in the manifold 34 and the plurality of heads 32 decreases as the ink is ejected from the plurality of heads 32, and the ink pressure gradually decreases. To do. Thereby, the pressure of the ink in the vicinity of the outflow port 641 (inside the cylinder 61) is also reduced, and the piston 62 moves to the second cover portion 64 side. As shown in FIG. 6, when the annular groove 624 of the piston 62 and the annular groove 612 on the inner peripheral surface of the cylinder 61 are connected and the inlet 611 is opened, ink is introduced from the inlet 611 into the cylinder 61. Flows in. Specifically, ink flows from the annular groove 612 of the cylinder 61 formed around the piston 62 into the annular groove 624 formed around the entire circumference of the piston 62, and flows into the hole 623 through the plurality of openings 625. . Then, the ink flows out from the outflow port 641, and the ink flows into the plurality of heads 32 via the manifold 34. As described above, the annular groove 624, the plurality of openings 625, and the hole 623 are ink flow paths inside the piston 62.

  When ink is replenished into the manifold 34 and the plurality of heads 32, the pressure of the ink in the interior and the vicinity of the outflow port 641 increases, and the piston 62 moves toward the first cover portion 63 side by the urging force of the urging portion 65. Return. As a result, the inlet 611 is closed by the side of the piston 62, and the inflow of ink into the cylinder 61 is stopped.

  As described above, the end surface 620a of the piston 62 is released to the atmospheric pressure, and the piston 62 is elastically urged toward the first cover portion 63 by the urging portion 65. When the difference from the ink pressure in the vicinity (lower than the atmospheric pressure) becomes higher (to some extent) than the pressure corresponding to the elastic force (biasing force) of the spring 652 of the urging portion 65, the piston 62 Moving toward the second cover portion 64, the inlet 611 is opened. Further, when the difference becomes lower (to some extent) than the pressure corresponding to the elastic force of the urging portion 65 due to the inflow of ink into the cylinder 61, the piston 62 moves toward the first cover portion 63. Thus, the inlet 611 is closed.

  In the actual operation of the pressure adjusting device 6 during printing, the opening and closing of the inflow port 611 due to the movement of the piston 62 in the direction of the central axis J1 is frequently repeated, and the pressure of ink inside the manifold 34 and the plurality of heads 32 is repeated. Is kept approximately constant. At this time, the inflow port 611 is formed so as to face the side portion of the piston 62, thereby preventing the ink pressure in the vicinity of the inflow port 611 from affecting the movement of the piston 62 in the direction of the central axis J1. The Further, the inflow port is set so that the ink pressure at the ejection port 321 of the head 32 disposed below the pressure adjusting device 6 is slightly lower than the atmospheric pressure (that is, slightly negative pressure). The elastic force of the urging portion 65 when the opening and closing of 611 are switched is adjusted, whereby an ink meniscus is formed in the discharge port 321 and ink leakage from the discharge port 321 is prevented ( The same applies to the pressure adjusting device 6a shown in FIG.

  Actually, an O-ring (not shown) made of resin having excellent chemical resistance such as PTFE (polytetrafluoroethylene) is provided between the inner peripheral surface of the cylinder 61 and the outer peripheral surface of the piston 62. The O-ring is fitted into a plurality of annular grooves formed on the outer peripheral surface of the piston 62, for example. In the state of FIG. 5, the plurality of annular grooves are preferably provided in the vicinity of both outer sides of the inflow port 611 in the direction of the central axis J1 and at a position between the annular groove 624 and the end surface 620a. As a result, the ink in the vicinity of the inlet 611 enters the cylinder 61 from between the piston 62 and the cylinder 61, and the outside air flows from the end surface 620a side through the gap between the piston 62 and the cylinder 61. Intrusion is prevented. An O-ring 613 is also provided between the second cover portion 64 and the cylinder 61, thereby preventing ink leakage. A predetermined liquid sealant (oil, grease, etc.) having a surface tension larger than that of ink is interposed between the inner peripheral surface of the cylinder 61 and the outer peripheral surface of the piston 62, so that the O-ring as described above is formed. It may be omitted.

  Here, assuming an ink jet printer of a comparative example that supplies ink in the ink tank to the head due to a water head difference, in such an ink jet printer, the ink tank is arranged in the vicinity of the ejection portion, and the ink in the ink tank is It is necessary to make the liquid level lower than the discharge port of the head. Therefore, the actual arrangement of the ink tank is limited to the side of the object holding portion (corresponding to the plurality of rollers 271 in FIG. 1) located in the vicinity of the ejection port of the head. For example, when performing maintenance on an ink jet printer, it is necessary to move the discharge unit to a position away from the holding unit in order to facilitate access to the discharge port of the head by an operator. In addition, due to the presence of the ink tank arranged on the side of the holding unit, various restrictions occur when the ejection unit is moved. In particular, when it is necessary to move the ejection unit to the side opposite to the ink tank with respect to the holding unit, a complicated operation of lifting and moving the ejection unit and the ink tank is required.

  In addition, by providing a negative pressure mechanism that makes the inside of the ink tank have a negative pressure, the ink tank can be disposed at a position other than the side of the holding portion (for example, above the head). It is not easy to keep the negative pressure constant. If the pressure in the ink tank changes greatly, the pressure of the ink held in the head also changes, and the ink landing position (relative landing position relative to the discharge port) on the substrate 9 and the discharge amount Etc. will occur. In the negative pressure mechanism, it may be possible to provide a pressure sensor, a buffer tank, etc. in addition to the pump to reliably control the negative pressure in the ink tank, but the structure of the mechanism is complicated and the manufacturing cost of the ink jet printer is increased. Will increase.

  On the other hand, in the ink jet printer 1, the pressure adjusting device 6 having the cylinder 61 and the piston 62 is provided in the supply flow path that connects the ink tank 52 and the head 32. In the pressure adjusting device 6, the urging portion 65 urges the piston 62 toward one side of the cylinder 61 in the direction of the central axis J1, thereby closing the inlet 611 formed in the cylinder 61 and discharging ink. As the pressure of the ink in the head 32 decreases, the piston 62 moves to the other side in the direction of the central axis J1, thereby opening the inlet 611. As a result, the closing and opening of the inlet 611 are switched at the boundary of the approximately constant pressure of the ink in the cylinder 61, and the pressure of the ink held in the head 32 is kept constant. As described above, the ink jet printer 1 has a simple configuration, and by using the pressure adjusting device 6 that can be manufactured at low cost, the arrangement of the ink tank 52 is not limited, and the ink held in the head 32 is not limited. The pressure can be kept constant. As a result, it is possible to prevent fluctuations in the landing position of the ink on the substrate 9 that occurs when the pressure of the ink in the head 32 changes, and high-precision printing (that is, creation of a high-quality printed matter). Is realized stably.

  Further, when the pressure around the inkjet printer 1 (atmospheric pressure in the present embodiment) changes due to the opening of the end surface 620a of the piston 62 on the first cover portion 63 side to the surroundings, It is possible to prevent a difference from the pressure of the ink in the head 32 from changing, and to change the meniscus state of the ink in the discharge port 321 significantly, or the ink discharge accuracy ( It is possible to prevent a decrease in accuracy regarding the discharge amount and the discharge position.

  FIG. 7 is a diagram illustrating another example of the pressure adjusting device. In the pressure adjusting device 6a in FIG. 7, another urging portion 66 is provided between the first cover portion 63a and the piston 62a, and the shapes of the first cover portion 63a and the piston 62a are the same as those in FIG. 6 and slightly different. Other configurations are the same as those in FIG.

  The urging portion 66 has a disc-shaped support plate 661 that is inserted into the cylinder 61 and has the center axis J1 as the center, and the support plate 661 has one end of a plurality of guide pins 662 parallel to the center axis J1. Is fixed. Similar to the guide pin 651 of the urging portion 65, the plurality of guide pins 662 are arranged at equiangular intervals in the circumferential direction around the central axis J1, and are arranged on the end surface 620a of the piston 62a on the first cover portion 63a side. A plurality of holes 622a into which a plurality of guide pins 662 can enter are formed. A plurality of springs (compression coil springs) 663 are fitted into the plurality of guide pins 662, one end of the spring 663 abuts on the support plate 661, and the other end abuts on the end surface 620a of the piston 62a. Further, the position of the support plate 661 in the direction of the central axis J1 can be adjusted by the amount of advancement / retraction of the bolt 633 provided on the first cover portion 63a. Thereby, it becomes possible to adjust the urging force by which the urging portion 66 urges the piston 62a toward the second cover portion 64 in the direction of the central axis J1.

  Also in the pressure adjusting device 6a of FIG. 7, the end surface 620a of the piston 62a is opened to the atmospheric pressure by the support plate 661 and the vent holes 664 and 632 of the first cover portion 63a. Further, in the normal state of the pressure adjusting device 6a, the maximum urging force (elastic force) that can be adjusted by the urging unit 66 is always smaller than the urging force by the urging unit 65. Therefore, in a state where the difference between the atmospheric pressure and the ink pressure in the vicinity of the outlet 641 is lower than the pressure corresponding to the difference in the magnitude of the urging force between the urging portions 65 and 66 (the sum of the elastic forces), the piston 62a approaches the first cover portion 63a, and the inlet 611 is closed. Further, when the difference between the atmospheric pressure and the ink pressure becomes higher (to some extent) than the pressure corresponding to the sum of the elastic forces, the piston 62a moves toward the second cover portion 64 and the inlet 611 is opened. Is done. In this way, the opening and closing of the inlet 611 due to the movement of the piston 62a in the direction of the central axis J1 is repeated, whereby the pressure of the ink inside the manifold 34 and the plurality of heads 32 is kept approximately constant. .

  As described above, in the pressure adjusting device 6a of FIG. 7, the urging force by the urging portion 66 that urges the piston 62a toward the second cover portion 64 in the direction of the central axis J1 can be adjusted. This makes it possible to change the pressure of the ink in the cylinder 61 when the inlet 611 is opened or closed, and to easily adjust the pressure of the ink in the head 32 that is kept approximately constant. The As a result, when manufacturing a plurality of ink jet printers 1, adjustment between printers (so-called machine difference adjustment) can be easily performed to prevent a difference in ink pressure in the head 32.

  FIG. 8 is a perspective view showing the appearance of an ink jet printer 1a according to the second embodiment of the present invention. In addition to the configuration of FIG. 1, the inkjet printer 1 a includes a chamber body 12 that accommodates the entire body 11 and a decompression pump 13 that decompresses the interior of the chamber body 12. Other configurations are the same as those in FIG. In FIG. 8, illustration of the control unit 4 is omitted.

  In the ink jet printer 1a of FIG. 8, by performing printing in a reduced pressure environment, the coffee stain phenomenon or the like is suppressed, and it is possible to form an ink image with a uniform film thickness on the substrate 9. Further, the plurality of heads 32 and the pressure adjusting device 6 (or the pressure adjusting device 6a) are placed in the same reduced pressure environment, and the end surface 620a of the piston 62 on the first cover portion 63 side is opened to the periphery. As described above, since the difference between the ambient pressure when the inlet 611 is opened or closed and the pressure of the ink in the cylinder 61 depends only on the urging force of the urging unit 65, in the inkjet printer 1a, The difference between the ambient pressure and the pressure of the ink in the head 32 can be made substantially the same as in an atmospheric pressure environment. Thereby, adjustments related to ink ejection can be easily performed under an atmospheric pressure environment. A gas supply unit (not shown) is connected to the chamber body 12, and a gas such as nitrogen is supplied into the chamber body 12 and returned to atmospheric pressure when the base material 9 is replaced.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  In the ink jet printer 1a of FIG. 8, the entire main body 11 including the ink tank 52 and the like is accommodated in the chamber main body 12. However, from the viewpoint of forming an ink image with high accuracy under a reduced pressure environment, It is only necessary that the head 32 for discharging ink, the transport unit 27 for moving the base material 9, and the pressure adjusting devices 6 and 6a for keeping the pressure of the ink in the head 32 constant are accommodated in the chamber body.

  In the first and second embodiments, the outlets 641 of the pressure adjusting devices 6 and 6a are directly connected to the manifold 34 to which the plurality of heads 32 are connected, whereby a plurality of pressure adjusting devices 6 and 6a are provided. The pressure adjusting devices 6 and 6a can promptly respond to the pressure fluctuation of the ink in the head 32 so that the pressure of the ink in the head 32 can be made constant with high accuracy. However, as shown in FIG. 9, even when the pressure adjusting device 6 is arranged on the supply line 51 at a position away from the head 32, the ink pressure in the head 32 is kept constant to some extent. Is possible. The pressure adjusting device 6, the manifold 34, and the head 32 shown in FIG. 9 may be provided inside the chamber body 12 shown in FIG. 8, and printing may be performed under a reduced pressure environment.

  Further, when it is not necessary to provide a plurality of heads 32 in the head unit 33, the pressure adjusting devices 6 and 6 a may be directly connected to the head 32. The pressure adjusting devices 6 and 6a that can be reduced in size by a simple configuration can be easily provided in the vicinity of the head 32.

  In the ink supply mechanism 5 of FIG. 3, the ink tank 52 may be disposed above the head unit 33 and the pressure adjusting devices 6 and 6a, and the pump 53 may be omitted. Even in this case, relatively high pressure ink is supplied in the vicinity of the inlet 611 of the pressure adjusting devices 6 and 6a, and the inlet 611 is repeatedly opened and closed as in the first and second embodiments. In addition, the pressure of the ink held in the head 32 can be kept constant. The pressure adjusting devices 6 and 6a may be used in an ink jet printer that circulates ink between an ink tank and a head.

  In the pressure adjustment device 6 of FIG. 5, the piston 62 may be biased toward the first cover portion 63 side by providing a tension spring between the piston 62 and the first cover portion 63. Further, the biasing of the piston may be realized by a magnetic force or the like. Further, when an ink jet printer is installed in a building provided with a common pressure reducing pipe, the spring 652 is omitted in the pressure adjusting device 6, and the plurality of vent holes 632 of the first cover portion 63 are depressurized via a regulator. It may be connected to a tube. In this case, the piston 62 is biased toward the first cover portion 63 side in the direction of the central axis J1 by the biasing portion including the pressure reducing pipe and the regulator, and the inflow port 611 is closed. Further, when the pressure of the ink in the cylinder 61 decreases due to the ejection of ink from the head 32, the piston 62 moves to the second cover portion 64 side, and the inlet 611 is opened.

  As described above, the pressure adjusting devices 6 and 6a shown in FIGS. 5 and 7 are merely examples, and the inflow port is closed by the urging portion that urges the piston toward one side in the axial direction of the cylinder, thereby discharging the ink. If the inflow port is opened by moving the piston to the other side in the axial direction as the pressure of the ink in the head decreases, the structure of the pressure adjusting device may be changed as appropriate.

  In the inkjet printers 1 and 1a, the substrate 9 moves at a constant speed in the scanning direction with respect to the ejection unit 3 by the transport unit 27. Depending on the design of the inkjet printer, a mechanism for moving the ejection unit 3 in the scanning direction. May be provided. In the inkjet printer, a stage that holds a rectangular base material and a stage moving mechanism that moves the stage in the scanning direction may be provided. Thus, the movement mechanism that moves the base material 9 relative to the discharge unit 3 can be realized in various configurations.

  In addition, in the inkjet printers 1 and 1a, one-pass printing is performed in which printing of an image on the base material 9 is completed only by the base material 9 passing once under the discharge unit 3 once. A plurality of discharge ports are arranged in the Y direction in FIG. 1, and a mechanism for moving the head 32 in the X direction is provided. The substrate 9 is moved in FIG. 1 each time the movement of the head 32 in the X direction is completed. Printing on the substrate 9 may be performed by moving in the Y direction by a distance corresponding to the width of the head 32.

  In addition to the sheet-like substrate 9, the printing object in the inkjet printers 1, 1 a may be a plate-like member or printing paper formed of plastic.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1,1a Inkjet printer 6,6a Pressure adjusting device 9 Base material 12 Chamber main body 27 Conveyance part 32 Head 34 Manifold 51 Supply line 52 Ink tank 61 Cylinder 62, 62a Piston 65, 66 Energizing part 321 Discharge port 611 Inflow port 620a End surface 623 hole 624 annular groove 625 opening 641 outflow port 652 spring J1 central axis

Claims (11)

An inkjet printer,
A head that ejects ink toward an object;
A moving mechanism for moving the object relative to the head;
An ink tank connected to the head via a supply flow path and storing ink;
A pressure adjusting device that is provided in the supply flow path, is sent from the ink tank to the head and is held constant in the head; and
With
The pressure adjusting device comprises:
An inlet provided on the ink tank side in the supply flow path, and a cylinder having an outlet provided on the head side;
A piston inserted into the cylinder;
A biasing portion that biases the piston toward one side in the axial direction of the cylinder and closes the inlet;
With
The piston moves to the other side in the axial direction in accordance with a decrease in the pressure of the ink in the head due to ink discharge, thereby opening the inlet and allowing ink to flow into the cylinder from the inlet. An ink jet printer, wherein ink flows out from an outlet to the head. The inkjet printer according to claim 1,
The inlet is formed on a side of the cylinder, facing the side of the piston;
An ink jet printer, comprising: a flow path through which ink flows into the cylinder from the inlet when the piston moves to the other side in the axial direction. The inkjet printer according to claim 1 or 2,
The biasing portion has an elastic member;
An ink jet printer, wherein an end face on the one side in the axial direction of the piston is opened to the periphery. An inkjet printer according to any one of claims 1 to 3,
The ink jet printer, wherein the pressure adjusting device further includes another urging portion that urges the piston toward the other side in the axial direction and adjusts the urging force. An ink jet printer according to any one of claims 1 to 4,
Another head having the same structure as the head;
A manifold that is part of the supply flow path and is connected to the head and the other head;
Further comprising
The ink jet printer, wherein the outlet of the pressure adjusting device is connected to the manifold. The inkjet printer according to claim 5,
The moving mechanism continuously moves the object in a predetermined scanning direction;
With respect to the arrangement direction perpendicular to the scanning direction and parallel to the recording surface of the object, a plurality of ejection ports in the plurality of heads connected to the manifold are arranged over the entire recording range of the recording surface. An ink jet printer characterized by the above. An ink jet printer according to any one of claims 1 to 6,
An ink jet printer comprising: a chamber main body that houses the head, the moving mechanism, and the pressure adjusting device, and that has a reduced pressure inside. Provided in a supply flow path that connects a head that discharges ink toward an object and an ink tank that stores ink, and is sent from the ink tank to the head via the supply flow path and within the head. A pressure adjusting device that maintains a constant pressure of ink to be held,
An inlet provided on the ink tank side in the supply flow path, and a cylinder having an outlet provided on the head side;
A piston inserted into the cylinder;
A biasing portion that biases the piston toward one side in the axial direction of the cylinder and closes the inlet;
With
The piston moves to the other side in the axial direction in accordance with a decrease in the pressure of the ink in the head due to ink discharge, thereby opening the inlet and allowing ink to flow into the cylinder from the inlet. A pressure adjusting device, wherein ink flows out from an outlet to the head. The pressure adjusting device according to claim 8, wherein
The inlet is formed on a side of the cylinder, facing the side of the piston;
The pressure adjusting device according to claim 1, further comprising: a flow path through which ink flows into the cylinder from the inlet when the piston moves to the other side in the axial direction. The pressure adjusting device according to claim 8 or 9, wherein
The biasing portion has an elastic member;
The pressure adjusting device according to claim 1, wherein an end face on the one side in the axial direction of the piston is opened to the periphery. The pressure adjusting device according to any one of claims 8 to 10,
The pressure adjusting device further includes another urging portion that urges the piston toward the other side in the axial direction and that can adjust the urging force.

Images