JP4968040B2 - Droplet discharge unit, droplet discharge head, and image forming apparatus having the same - Google Patents

Droplet discharge unit, droplet discharge head, and image forming apparatus having the same Download PDF

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Publication number
JP4968040B2
JP4968040B2 JP2007324655A JP2007324655A JP4968040B2 JP 4968040 B2 JP4968040 B2 JP 4968040B2 JP 2007324655 A JP2007324655 A JP 2007324655A JP 2007324655 A JP2007324655 A JP 2007324655A JP 4968040 B2 JP4968040 B2 JP 4968040B2
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Prior art keywords
liquid
droplet discharge
flow path
circulation amount
ejector
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JP2009143168A (en
Inventor
政行 工藤
進 平潟
信二 瀬戸
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富士ゼロックス株式会社
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, e.g. INK-JET PRINTERS, THERMAL PRINTERS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01Ink jet
    • B41J2/015Ink jet characterised by the jet generation process
    • B41J2/04Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/055Devices for absorbing or preventing back-pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, e.g. INK-JET PRINTERS, THERMAL PRINTERS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01Ink jet
    • B41J2/135Nozzles
    • B41J2/14Structure thereof only for on-demand ink jet heads
    • B41J2/14201Structure of print heads with piezoelectric elements
    • B41J2/14233Structure of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, e.g. INK-JET PRINTERS, THERMAL PRINTERS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01Ink jet
    • B41J2/135Nozzles
    • B41J2/14Structure thereof only for on-demand ink jet heads
    • B41J2/14201Structure of print heads with piezoelectric elements
    • B41J2002/14306Flow passage between manifold and chamber
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, e.g. INK-JET PRINTERS, THERMAL PRINTERS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01Ink jet
    • B41J2/135Nozzles
    • B41J2/14Structure thereof only for on-demand ink jet heads
    • B41J2002/14419Manifold
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, e.g. INK-JET PRINTERS, THERMAL PRINTERS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2202/00Embodiments of or processes related to ink-jet or thermal heads
    • B41J2202/01Embodiments of or processes related to ink-jet heads
    • B41J2202/12Embodiments of or processes related to ink-jet heads with ink circulating through the whole print head

Description

  The present invention relates to a droplet discharge unit and a droplet discharge head that discharge droplets, and an image forming apparatus including the droplet discharge unit and the droplet discharge head.

  In Patent Document 1, in order to prevent thickening of the droplets ejected from the nozzles of the droplet ejection head, vibration is applied to the meniscus of the idle nozzle, or droplets are ejected from the nozzles regardless of image formation. Technology is disclosed.

  Specifically, the image forming apparatus is configured to intermittently vibrate the meniscus of the nozzle to the extent that the liquid droplet is not discharged at the time of liquid droplet discharge standby without discharging the liquid droplet from the nozzle, and after the liquid droplet is discharged from the nozzle. And a step of retracting the droplet discharge head to a retract position irrelevant to image formation after a predetermined time has elapsed and discharging the droplet from the nozzle.

  In other words, when waiting for droplet ejection, the same vibration is applied to the meniscus of all nozzles to prevent the viscosity of the droplet from rising, and after a certain period of time, the droplet ejection head is retracted to a retracted position unrelated to image formation. The droplets are discharged from the nozzle.

In this way, by combining the two steps, it is possible to stably discharge liquid droplets from the nozzle by preventing an increase in the viscosity of the liquid existing in the vicinity of the nozzle.
Japanese Patent Laid-Open No. 9-29996

  However, since this image forming apparatus has a structure in which the same vibration is applied to the meniscus of all the nozzles, it is necessary to vibrate the meniscus of all the nozzles according to the most severe conditions. It was increasing.

  An object of the present invention is to suppress the increase in the viscosity of the liquid existing in the vicinity of the nozzle while suppressing the increase in power consumption in consideration of the above facts.

A droplet discharge unit according to claim 1 of the present invention includes a nozzle that discharges a droplet, a pressure chamber that communicates with the nozzle via a communication path, and an actuator that applies pressure to the liquid in the pressure chamber. A plurality of ejectors, a first fluid flow path through which liquid supplied to the pressure chamber of the ejector flows, and a second fluid into which liquid supplied from the first fluid flow path to the pressure chamber flows through the communication path The vicinity of the nozzle based on the flow rate, the circulation means for circulating the liquid from the ejector to the ejector through the first fluid flow channel, and the second fluid flow channel from the ejector, and the circulation amount of the liquid circulating in each of the ejectors The preliminary waveform for stirring the liquid is driven by changing the application time by reducing the voltage applied to the actuator relative to the main waveform for ejecting droplets from the nozzle. Comprising a part, wherein the drive control unit, when the circulation amount is small, as compared with the case often, and applying the preliminary waveform to the actuator to increase the application time.

  According to the above configuration, the liquid flowing from the ejector to the second fluid flow path is circulated in the ejector through the first fluid flow path to the ejector by the circulation means.

  Specifically, when the circulation means is activated, the liquid flows through the first fluid flow path into the pressure chamber of the ejector. The liquid flowing into the pressure chamber passes through the communication path of the ejector and circulates through the second fluid flow path. In this way, the liquid in each ejector circulates.

  Here, the drive control unit changes the pressure applied to the liquid in the pressure chamber by applying different preliminary waveforms to the actuator based on the circulation amount of the liquid circulating through each ejector, and vibrates the meniscus of the nozzle. Thereby, the meniscus of each nozzle is vibrated, and the increase in the viscosity of the liquid discharged from the nozzle is suppressed.

  That is, a large preliminary waveform is applied to an ejector with a small circulation amount to greatly vibrate the meniscus, and a small preliminary waveform is applied to an ejector with a large circulation amount.

  As described above, by applying different preliminary waveforms based on the circulation amount, an increase in power consumption can be suppressed, and an increase in the viscosity of the liquid existing in the vicinity of the nozzle can be suppressed.

  The droplet discharge unit according to a second aspect of the present invention is the liquid droplet ejection unit according to the first aspect, wherein the circulation amount is calculated based on flow path resistances of the first fluid channel and the second fluid channel. It is characterized by.

  According to the above configuration, the circulation amount of the liquid is calculated based on the channel resistances of the first fluid channel and the second fluid channel. For this reason, it is not necessary to directly measure the flow rate of the liquid flowing through each ejector.

  The droplet discharge unit according to a third aspect of the present invention is the liquid droplet ejection unit according to the first or second aspect, wherein the drive control unit is different from the actuator of the ejector divided into a plurality of groups based on the circulation amount. A preliminary waveform is applied.

  According to the above configuration, the drive control unit applies different preliminary waveforms to the actuators of the ejectors divided into a plurality of groups based on the circulation amount. For this reason, the drive control of the actuator is not complicated.

The droplet discharge unit according to a fourth aspect of the present invention is the droplet discharge unit according to any one of the first to third aspects, wherein the drive control unit is configured to have a channel resistance of the first fluid channel and the second fluid channel. and characterized by applying different the preliminary waveform to the actuator based on the circulation amount calculated by the viscosity of the liquid flowing through the ejector.

  According to the above configuration, the drive control unit applies different preliminary waveforms to the actuator based on the type of liquid flowing through the ejector.

  For example, in the case of a liquid having a high viscosity, a large preliminary waveform is applied to vibrate the meniscus, and in the case of a liquid having a low viscosity, a small preliminary waveform is applied.

  In this manner, by applying a preliminary waveform that matches the properties of the liquid, it is possible to stably discharge liquid droplets from the nozzle by effectively suppressing the increase in viscosity of the liquid discharged from the nozzle.

  An image forming apparatus according to a fifth aspect of the present invention includes the droplet discharge unit according to any one of the first to fourth aspects.

  According to the above configuration, since the image forming apparatus includes the droplet discharge unit according to any one of claims 1 to 4, a high-quality output image without missing a dot can be obtained.

A droplet discharge head according to claim 6 of the present invention includes a nozzle that discharges a droplet, a pressure chamber that communicates with the nozzle via a communication path, and an actuator that applies pressure to the liquid in the pressure chamber. A plurality of ejectors, a first fluid channel through which the liquid supplied to the pressure chamber of the ejector flows, and a second through which the liquid supplied from the first fluid channel to the pressure chamber flows through the communication passage. A plurality of droplet discharge units comprising a fluid channel, a first common channel for supplying a liquid to the first fluid channel of each of the droplet discharge units, and the first common channel from the first common channel A second common channel through which the liquid supplied to the droplet ejection unit through the first fluid channel flows through the second fluid channel of the droplet ejection unit; and the droplet ejection unit through the first common channel. To the liquid And circulation means for a discharge unit circulates liquid through the second common channel, based on the circulation rate of the liquid circulating said ejectors each, the preliminary waveform for agitating the liquid in the vicinity of the nozzles, the liquid from the nozzle A drive control unit that reduces the voltage applied to the actuator to change the application time with respect to the main waveform for ejecting droplets, and the drive control unit is smaller when the circulation amount is small than when the circulation amount is large. The preliminary waveform is applied to the actuator so as to lengthen the application time.

  According to the above configuration, the liquid flowing through the first common channel to the droplet ejection unit and further from the droplet ejection unit to the second common channel is circulated in the plurality of droplet ejection units by the circulation means. .

  Specifically, when the circulation means is activated, the liquid passes through the first common flow path, and further branches from the first common flow path and flows into the first fluid flow path of each droplet discharge unit, and the pressure of each ejector. Flow into the room.

  In addition, the liquid that has flowed into the pressure chamber passes through the communication path of the ejector, flows into the second common flow path through the second fluid flow path. In this way, the liquid in each droplet discharge unit circulates.

  Here, the drive control unit changes the pressure applied to the liquid in the pressure chamber by applying different preliminary waveforms to the actuator based on the circulation amount of the liquid flowing through each ejector, and vibrates the meniscus of the nozzle. Thus, the meniscus of each nozzle is vibrated, and the increase in the viscosity of the liquid discharged from the nozzle is suppressed.

  That is, a large preliminary waveform is applied to an ejector with a small circulation amount to greatly vibrate the meniscus, and a small preliminary waveform is applied to an ejector with a large circulation amount.

  In this way, by applying different preparatory waveforms based on the circulation amount, the increase in power consumption is suppressed, and the increase in the viscosity of the liquid discharged from the nozzle is suppressed, and the liquid droplets are stably discharged from the nozzle. Can be made.

  The droplet discharge head according to a seventh aspect of the present invention is the liquid droplet ejection head according to the sixth aspect, wherein the circulation amount includes the first fluid channel, the second fluid channel, the first common channel, and the second fluid channel. It is calculated based on the channel resistance of the common channel.

  According to the above configuration, the circulation amount of the liquid is calculated based on the channel resistances of the first fluid channel, the second fluid channel, the first common channel, and the second common channel. For this reason, it is not necessary to directly measure the flow rate of the liquid flowing through each ejector.

  The droplet discharge head according to an eighth aspect of the present invention is the liquid droplet ejection head according to the sixth or seventh aspect, wherein the drive control unit is different from the actuator of the ejector divided into a plurality of groups based on the circulation amount. A preliminary waveform is applied.

  According to the above configuration, the drive control unit applies different preliminary waveforms to the actuators of the ejectors divided into a plurality of groups based on the circulation amount of the liquid. For this reason, the drive control of the actuator is not complicated.

Droplet discharging head according to claim 9 of the present invention, in claim 6-8 What Re preceding paragraphs, wherein the drive control unit, the flow passage of the first fluid passage and the second fluid flow path resistance, and characterized by applying the preliminary waveform different to the actuator based on the circulation amount calculated by the circulation amount calculated by the viscosity of the liquid flowing through the ejector.

  According to the above configuration, the drive control unit applies different preliminary waveforms to the actuator based on the type of liquid flowing through the ejector.

  For example, in the case of a liquid having a high viscosity, a large preliminary waveform is applied to vibrate the meniscus, and in the case of a liquid having a low viscosity, a small preliminary waveform is applied.

  Thus, by applying a preliminary waveform that matches the properties of the liquid, it is possible to effectively suppress the thickening of the liquid ejected from the nozzle.

  An image forming apparatus according to a tenth aspect of the present invention includes the liquid droplet ejection head according to any one of the sixth to ninth aspects.

  According to the above configuration, since the image forming apparatus includes the droplet discharge head according to any one of claims 6 to 9, a high-quality output image without missing a dot can be obtained.

  According to the present invention, it is possible to suppress an increase in the viscosity of a liquid existing in the vicinity of a nozzle while suppressing an increase in power consumption.

  A first embodiment of an image forming apparatus employing a droplet discharge unit of the present invention will be described with reference to FIGS.

(overall structure)
As shown in FIG. 5, an inkjet recording apparatus 10 as an image forming apparatus includes a carriage 14 on which a droplet discharge unit 12 is mounted, a main scanning mechanism 16 that scans the carriage 14 along the main scanning direction M, A sub-scanning mechanism 18 that transports the sheet material P along the sub-scanning direction S and a maintenance station 20 are provided.

  The droplet discharge unit 12 is mounted on the carriage 14 such that the nozzle plate 32 (see FIG. 2) on which the nozzles 30 are formed is opposed to the sheet material P as a recording medium, and the main scanning mechanism 16 performs the main scanning direction M. By ejecting ink droplets as droplets from the nozzle 30 while moving to the position, an image is recorded on a certain band region BE of the sheet material P. When one movement in the main scanning direction is completed, the sheet material P is conveyed in the sub scanning direction S by the sub scanning mechanism 18, and the carriage 14 moves in the main scanning direction M again to record the band region BE. By repeating such an operation a plurality of times, image recording can be performed over the entire surface of the sheet material P.

(Main part configuration)
As shown in FIG. 1, the droplet discharge unit 12 is provided with ejectors 26 provided with nozzles 30 for discharging droplets arranged in three rows. Further, a first branch channel 34 that supplies ink to each ejector 26 is provided adjacent to each row of ejectors 26 so as to extend in the row direction of the ejectors 26. A second branch channel 36 through which the ink discharged from the ejector 26 flows is provided so as to extend in the column direction of the ejector 26 on the opposite side of the first branch channel 34 across the ejectors 26 in each column. .

  Further, a first main channel 38 for supplying ink to each first branch channel 34 is provided at the end of each first branch channel 34 (lower end portion shown in FIG. 1). It extends in a direction crossing the direction.

  Further, a second main flow path 40 into which ink discharged through each second branch flow path 36 flows is provided at the end portion (upper end portion shown in FIG. 1) of each second branch flow path 36. It extends in a direction crossing the longitudinal direction of the path 36.

  Further, a liquid tank 42 in which ink to be supplied to the ejector 26 is stored is provided, and an end portion (left end portion shown in FIG. 1) of the first main flow path 38 is connected to a flow path pipe 44 having a sufficiently small flow path resistance. Via the liquid tank 42. Further, the end portion (the right end portion shown in FIG. 1) of the second main channel 40 is communicated with the liquid tank 42 via a channel tube 46 having a sufficiently small channel resistance.

  Further, a circulation pipe 48 as a circulation means is provided in the flow path pipe 46 that communicates the liquid tank 42 and the second main flow path 40. When the circulation pump 48 is operated, the ink stored in the liquid tank 42 is provided. However, it flows from the liquid tank 42 through the first main flow path 38 through the flow path pipe 44, and further flows through the first branch flow path 34 that branches off from the first main flow path 38, and the pressure chambers 50 ( (See FIG. 2). Further, the ink that has flowed into the pressure chamber 50 passes through the communication path 76 (see FIG. 2) of the ejector 26, flows through the second branch flow path 36, and flows into the second main flow path 40. Then, the ink that has flowed into the second main flow path 40 flows through the flow path pipe 46 and is collected into the liquid tank. In this way, ink circulates between each ejector 26 and the liquid tank 42.

  As shown in FIG. 2, the ejector 26 includes a nozzle 30 that ejects ink droplets (droplets), a pressure chamber 50 that communicates with the nozzles 30 through the communication path 76 and applies pressure to the ink, and a pressure An actuator 51 that applies pressure to the ink in the chamber 50 is provided. The drive actuator 51 includes a plate-like diaphragm 74 and a drive element 52. A circuit board 57 is provided on the upper electrode 53 of the drive element 52 via a solder bump 55.

  The first branch flow path 34 is disposed between the rows of the ejectors 26, and a part of the first branch flow path 34 is disposed so as to overlap the ejectors 26 when viewed from the nozzle surface.

  Further, the second branch flow path 36 is disposed between the rows of the ejectors 26 and communicates with each ejector 26, and the ink discharged from each ejector 26 passes through the second branch flow path 36 to the second main flow path 40 ( (See FIG. 1).

  Further, the droplet discharge unit 12 according to the present embodiment includes a recess forming plate 54, a nozzle plate 32, a discharge path forming plate 56, a discharge hole forming plate 58, a branch channel forming plate 60, a resin plate 62, and a branch channel forming. A plate 64, a first supply hole forming plate 66, a supply path forming plate 68, a second supply hole forming plate 70, a pressure chamber forming plate 72, a vibration plate 74, and a drive element 52 are provided.

  Then, the recess forming plate 54, the nozzle plate 32, the discharge path forming plate 56, the discharge hole forming plate 58, the branch flow path forming plate 60, the resin plate 62, the branch flow path forming plate 64, the first supply hole forming plate 66, the supply The path forming plate 68, the second supply hole forming plate 70, the pressure chamber forming plate 72, the vibration plate 74, and the driving element 52 are stacked in this order.

  A nozzle 30 for discharging ink droplets is formed on the nozzle plate 32. A recess 54 </ b> A is formed on the periphery of the nozzle 30 in the recess forming plate 54. The recess 54 </ b> A is a step formed at the periphery of the nozzle 30, and the portion where the nozzle 30 is formed is retracted from the surrounding plate surface, for example, the periphery of the nozzle 30 is caused by friction due to contact with the sheet material P. In addition, mechanical friction caused by wiping the nozzle surface is avoided.

  A pressure chamber 50 is formed in the pressure chamber forming plate 72 so as to communicate with the nozzle 30 and to apply a pressure for discharging the ink. The pressure chamber 50 includes a discharge passage forming plate 56, a discharge hole forming plate 58, a branch passage forming plate 60, a resin plate 62, a branch passage forming plate 64, a first supply hole forming plate 66, a supply passage forming plate 68, and It communicates with the nozzle 30 via a communication path 76 formed in the second supply hole forming plate 70, and ink can flow from the pressure chamber 50 to the nozzle 30.

Further, a first branch flow path 34 is formed in the branch flow path forming plate 64, and a supply path 78 that supplies ink from the first branch flow path 34 to each pressure chamber 50 is supplied to the supply path forming plate 68. Is formed.

  The supply path 78 communicates with the first branch flow path 34 via the first supply hole 80 formed in the first supply hole forming plate 66. Further, the supply path 78 communicates with the pressure chamber 50 via a second supply hole 82 formed in the second supply hole forming plate 70.

  On the other hand, a discharge path 84 communicating with the communication path 76 is formed in the discharge path forming plate 56 stacked immediately above the nozzle plate 32. The discharge path 84 communicates with the second branch flow path 36 via a discharge hole 86 formed in the discharge hole forming plate 58.

Further, in order to make the resin plate 62 work efficiently as a damper for preventing crosstalk, the branch flow path forming plate 60 and the branch flow path forming plate 64 include the first branch flow path 34 and the second branch flow path. 36, the cavity of the damper chambers 45 and 47 is formed in the opposite side region across the resin plate 62. With this configuration, the ink flowing into the ejector 26 from the first branch flow path 34 is supplied to the first supply hole 80, It flows to the pressure chamber 50 through the supply path 78 and the second supply hole 82. The ink that has flowed into the pressure chamber 50 passes through the communication path 76, flows above the nozzle 30, flows through the discharge path 84 and the discharge hole 86, and is discharged to the second branch flow path 36.

  Further, based on the circulation amount of the ink flowing through the respective ejectors 26 by the circulation pump 48 (see FIG. 1), a different preliminary waveform is applied to the drive element 52 via the circuit board 57 to apply pressure to the liquid in the pressure chamber 50. And a drive control unit 88 that vibrates the meniscus of the nozzle 30 is provided. The preliminary waveform is a waveform for stirring the ink in the vicinity of the nozzle 30 in order to prevent an increase in the viscosity of the ink, unlike the main waveform for ejecting ink from the nozzle 30.

  With this configuration, when the drive control unit 88 that controls the drive waveform applied to the drive element 52 applies the preliminary drive waveform to the drive element 52 via the circuit board 57, the drive element 52 uses the ink filled in the pressure chamber 50. By pressurizing, the ink existing in the pressure chamber 50 and the communication path 76 is agitated.

(Action / Effect)
Here, the inventor of the present application determines the circulation amount of the ink flowing to each ejector 26 by using the first fluid channel 92 including the first branch channel 34 and the first main channel 38, the second branch channel 36, and the like. The calculation was made based on the flow resistance of the second fluid flow path 94 composed of the second main flow path 40.

  As shown in FIG. 1, the group of the ejectors 26 with the smallest ink circulation amount is the ejectors 26 arranged in the range A arranged in the vicinity of the substantially central portion of the ejectors 26 arranged in a matrix. . These ejectors 26 were set as group A.

  Furthermore, the group of the ejectors 26 having the smallest circulation amount after the group A was the ejectors 26 arranged in the range B arranged so as to surround the range A. These ejectors 26 were designated as group B.

  The ejector 26 having a large circulation amount arranged in the range C outside the range B is set as a group C. In this way, the ejectors 26 were classified into three groups based on the circulation amount.

  First, the present inventor applied the same preliminary waveform to the ejectors 26 divided into these three groups, and then applied this waveform to eject ink droplets from the nozzle 30 and confirmed the droplet velocity of the ink droplets. .

  4A, 4 </ b> B, and 4 </ b> C show the preliminary waveform and the main waveform applied to the driving element 52 through the circuit board 57, where the vertical axis represents voltage and the horizontal axis represents time. Then, a preliminary waveform having the shortest application time (pulse width) shown in FIG. 4A was applied to all the ejectors 26 before this waveform.

  FIG. 3A shows the drop speed of the ink droplet when the main waveform is applied after the preliminary waveform and the ink droplet is ejected from the nozzle 30, and the horizontal axis is the last ejected ink droplet from the nozzle 30. This is the time elapsed from the time, and the vertical axis indicates the ink droplet velocity.

  With respect to the ink droplets ejected from the ejector 26 of the group A having the smallest ink circulation amount, the droplet speed is greatly reduced when the ink droplets are ejected after a certain amount of time has elapsed since the last ink droplet ejection. I understand that. On the other hand, with respect to the ink droplets ejected from the ejector 26 of the group C having the largest ink circulation amount, the droplet speed is almost reduced even if the ink droplets are ejected after a certain time has elapsed since the last ink droplet ejection. You can see that they are not.

  That is, it can be seen that the preliminary waveform shown in FIG. 4A is insufficient for the ejector 26 of group A with a small circulation amount. In this embodiment, the droplet speed is 10 m / s as a reference, and the target is to secure a droplet speed of 8 m / s or more in order to prevent the output image from being lowered even when the droplet speed is lowered.

  Accordingly, the drive control unit 88 shown in FIG. 2 applies a different preliminary waveform to the drive element 52 for each group.

  In detail, the preliminary waveform shown in FIG. 4C having the longest pulse width is applied to the ejector 26 of the group A having the smallest circulation amount, and then the ejector 26 of the group B having the smallest circulation amount is applied. The preliminary waveform shown in FIG. 4 (B) having a pulse width shorter than the pulse width of the preliminary waveform shown in FIG. 4 (C) was applied. Then, the preliminary waveform shown in FIG. 4A having the shortest pulse width was applied to the ejector 26 of group C having the largest circulation amount.

  As shown in FIG. 3B, when the drive control unit 88 (see FIG. 2) applies a different preliminary waveform to the drive element 52 based on the ink circulation amount, the ink droplet velocity after the preliminary waveform application is The target was 8 m / s or more for all groups.

  In this way, the drive control unit 88 applies a different preliminary waveform to the drive element 52 based on the circulation amount of the ink flowing through the ejector 26, so that the power consumption is compared with the case where the same preliminary waveform is applied. In addition, the increase in the viscosity of the ink existing in the vicinity of the nozzle 30 can be suppressed, and the ink can be stably ejected from the nozzle 30.

  Further, the drive control unit 88 generates a different preliminary waveform for the drive element 52 based on the circulation amount calculated based on the flow resistance of the first fluid flow path 92 and the second fluid flow path 94 (see FIG. 1). Apply. For this reason, it is not necessary to directly measure the flow rate of the ink flowing through each ejector 26.

  In addition, when an optimum drive waveform is set for each ejector, the drive control becomes complicated, the cost of the drive unit increases, and the processing speed becomes slow. However, in the present invention, the drive control unit 88 is Different preliminary waveforms are applied to the drive elements 52 of the ejector 26 divided into a plurality of groups (in the present embodiment, groups A, B, and C) based on the circulation amount. For this reason, the drive control of the actuator 51 is not complicated.

  In addition, since the ink can be stably ejected from the nozzles 30, a high-quality output image without missing dots can be obtained.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It is clear to the contractor. For example, in the above-described embodiment, different preliminary waveforms are created by changing the pulse width of the preliminary waveform. However, by changing parameters such as the pulse width, voltage, and frequency, or by changing each parameter in combination. Different preliminary waveforms may be created.

  In the above embodiment, the preliminary waveform is applied only once before the main waveform for ejecting ink. However, the preliminary waveform may be applied continuously after the nozzle 30 finally ejects ink droplets. .

  Next, a second embodiment of the image forming apparatus employing the droplet discharge unit of the present invention will be described with reference to FIGS.

  In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 6, in this embodiment, unlike the first embodiment, two droplet discharge units 12 are provided. Different types of liquid are stored in the liquid tank 42 and the liquid tank 96 of each droplet discharge unit 12.

  Specifically, the liquid tank 42 stores colored ink that is discharged onto the sheet material P to form an image, and the liquid tank 96 is discharged from the processing liquid (for example, discharged first onto the sheet material P and then discharged later). Liquid that controls the fixing of the ink to be applied and enhances the image quality) is stored.

  Here, the inventor of the present application determines the circulation amount of the ink flowing to each ejector 26 by the first fluid channel 92, the second branch channel 36, and the first branch channel 36 configured by the first branch channel 34 and the first main channel 38. The calculation was made based on the flow resistance of the second fluid flow path 94 composed of the two main flow paths 40 and the type of liquid (for example, the viscosity of the liquid).

  As shown in FIG. 6, as in the first embodiment, for the ejector 26 through which ink stored in the liquid tank 42 flows, the group of the ejector 26 with the least circulating amount is the ejector 26 arranged in a matrix. The ejector 26 is disposed in the range A disposed in the vicinity of the substantially central portion. These ejectors 26 were set as group A. Further, as in the first embodiment, the ejector 26 arranged in the range B is set as a group B, and the ejector 26 arranged in the range C is set as a group C.

  On the other hand, for the ejector 26 through which the processing liquid stored in the liquid tank 96 flows, the group of the ejector 26 with the smallest circulation amount is within the range A ′ disposed in the vicinity of the substantially central portion of the ejector 26 disposed in a matrix. It was the ejector 26 arrange | positioned. These ejectors 26 were set as group A ′. Further, as in the first embodiment, the ejectors 26 arranged in the range B ′ are set as a group B ′, and the ejectors 26 arranged in the range C ′ are set as a group C ′.

  The ink circulation amount increases in the order of group A, group B, group A ′, group B ′, group C, and group C ′.

  First, the present inventor applied the same preliminary waveform to the ejectors 26 divided into these six groups, and then applied this waveform to cause ink droplets to be ejected from the nozzles 30 and confirmed the droplet velocity of the ink droplets. .

  8A, 8B, 8C, 8D, and 8E show the preliminary waveform and the main waveform applied to the 52 driving element 52 via the circuit board 57, where the vertical axis represents voltage and the horizontal axis represents time. To express. Then, the preliminary waveform having the shortest application time (pulse width) shown in FIG. 8A was applied to all the ejectors 26 before this waveform.

  FIG. 7A shows the drop speed of the ink droplet when the main waveform is applied after the preliminary waveform and the ink droplet is ejected from the nozzle 30, and the horizontal axis is the last ejected ink droplet from the nozzle 30. This is the time elapsed from the time, and the vertical axis indicates the ink droplet velocity.

  With respect to the ink droplets ejected from the ejector 26 of the group A with the smallest circulation amount, if the ink droplets are ejected after a certain amount of time has elapsed since the last ejection of the ink droplets, the droplet speed is greatly reduced. I understand. On the other hand, with respect to the ink droplets ejected from the ejectors 26 of the group C and the group C ′ having a large circulation amount, the droplet velocity is almost the same even if the ink droplets are ejected after a certain time has elapsed since the last ink droplet ejection. It turns out that it has not fallen.

  That is, it can be seen that the preliminary waveform shown in FIG. 8A is insufficient for the ejector 26 of group A with a small circulation amount. In this embodiment, the droplet speed is 10 m / s as a reference, and the target is to secure a droplet speed of 8 m / s or more in order to prevent the output image from being lowered even when the droplet speed is lowered.

  Therefore, the drive control unit 88 applied a preliminary waveform different for each group to the drive element 52.

  Specifically, the preliminary waveform shown in FIG. 8E having the longest pulse width is applied to the ejector 26 of the group A having the smallest circulation amount, and the ejector 26 of the group B having the next smallest circulation amount is applied to the ejector 26 having the smallest circulation amount. A preliminary waveform shown in FIG. 8D having a pulse width shorter than the pulse width of the preliminary waveform shown in FIG. 8E was applied. Further, the preliminary waveform shown in FIG. 8C having a pulse width shorter than the pulse width of the preliminary waveform shown in FIG. 8D was applied to the ejector 26 of the group A ′ having the next smallest circulation amount. Further, the preliminary waveform shown in FIG. 8B having a pulse width shorter than the pulse width of the preliminary waveform shown in FIG. 8C was applied to the ejector 26 of the group B ′ having the next smallest circulation amount.

  A preliminary waveform shown in FIG. 8A having the shortest pulse width was applied to the ejectors 26 of the group C and the group C ′ having a large circulation amount.

  As shown in FIG. 7B, when the drive control unit 88 applies a different preliminary waveform to the drive element 52 based on the ink circulation amount, the ink droplet speed after the preliminary waveform application is the target in all groups. Of 8 m / s or more.

  In this way, by applying the preliminary waveform in consideration of the properties of the liquid, it is possible to effectively suppress the thickening of the liquid ejected from the nozzle, and to stably eject liquid droplets from the nozzle. Can do.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It is clear to the contractor. For example, in the above-described embodiment, different preliminary waveforms are created by changing the pulse width of the preliminary waveform. However, by changing parameters such as the pulse width, voltage, and frequency, or by changing each parameter in combination. Different preliminary waveforms may be created.

  In the above embodiment, the preliminary waveform is applied only once before the main waveform for ejecting ink. However, the preliminary waveform may be applied continuously after the nozzles eject ink droplets last.

  Next, a third embodiment of the image forming apparatus in which the droplet discharge head of the present invention is employed will be described with reference to FIGS.

  In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 11, in this embodiment, unlike the first embodiment, the ink jet recording apparatus 110 as an image forming apparatus includes a plurality of liquid droplet ejection units 98 (see FIG. 9). A discharge head 112 is provided. Hereinafter, the ink jet recording apparatus 110 will be described.

(overall structure)
A sheet feeding tray 116 is provided in the lower part of the casing 114 of the ink jet recording apparatus 110, and the sheet material P stacked in the sheet feeding tray 116 can be taken out one by one by a pickup roll 118. The taken sheet material P is transported by a plurality of transport rollers 120 constituting a predetermined transport path 122. Hereinafter, the “transport direction” simply refers to the transport direction of the sheet material P, which is a recording medium, and “upstream” and “downstream” refer to upstream and downstream in the transport direction, respectively.

  Above the paper feed tray 116, an endless transport belt 128 stretched between a drive roll 124 and a driven roll 126 is disposed. A recording head array 130 is disposed above the conveyor belt 128 and faces the flat portion 128F of the conveyor belt 128. This opposed area is an ejection area SE from which droplets are ejected from the recording head array 130. The sheet material P conveyed on the conveyance path 122 is held by the conveyance belt 128 and reaches the discharge area SE, and in a state of facing the print head array 130, droplets corresponding to image information are discharged from the print head array 130. Is done.

  Then, by rotating the sheet material P while being held by the conveyance belt 128, the sheet material P can be passed through the ejection region SE a plurality of times, and so-called multipass image recording can be performed. Therefore, the surface of the conveyance belt 128 is a circulation path of the sheet material P.

  Furthermore, the recording head array 130 has a long shape in which the effective recording area is equal to or larger than the width of the sheet material P (the length in the direction orthogonal to the conveyance direction), and is yellow (Y), magenta (M), cyan. Four droplet discharge heads 112 corresponding to each of the four colors (C) and black (K) are arranged along the transport direction, and a full-color image can be recorded.

  The recording head array 130 may be stationary in a direction orthogonal to the transport direction. However, if the recording head array 130 is configured to move as necessary, an image with higher resolution can be obtained by multipass image recording. It is possible to record, or to prevent the malfunction of the droplet discharge head 112 from being reflected in the recording result. Details of the droplet discharge head 112 will be described later.

  Furthermore, four maintenance units 134 corresponding to the respective droplet discharge heads 112 are arranged in the vicinity of the recording head array 130 (in this embodiment, both sides in the transport direction). The maintenance unit 134 performs a predetermined maintenance operation (vacuum, dummy jet, wiping, capping, etc.).

  A charging roll 136 is disposed on the upstream side of the recording head array 130. The charging roll 136 is driven between the driven roll 126 while sandwiching the conveyance belt 128 and the sheet material P, and between a pressing position where the sheet material P is pressed against the conveyance belt 128 and a separation position separated from the conveyance belt 128. Can be moved. At the pressing position, a predetermined potential difference is generated between the driven roll 126 and the ground, so that the sheet material P can be charged and electrostatically attracted to the conveying belt 128.

  A peeling plate (not shown) is disposed on the downstream side of the recording head array 130 so that the sheet material P is peeled from the conveying belt 128.

  The peeled sheet material P is conveyed by a plurality of discharge rollers 142 constituting a discharge path 144 and discharged to a paper discharge tray 146 provided at the top of the housing 114.

  In addition, a reversing path 152 composed of a plurality of reversing rollers 150 is provided between the paper feed tray 116 and the conveying belt 128, and the conveying belt 128 reverses the sheet material P on which an image is recorded on one side. Thus, image recording on both surfaces of the sheet material P can be easily performed.

  Such an ink jet recording apparatus 110 includes four droplet discharge heads 112 that contain four colors of ink. Therefore, the head width in the conveyance direction of the sheet material P can be reduced, and the small size The recording head array 130 can be realized.

(Main part configuration)
Next, the configuration of the droplet discharge head 112 will be described.

  As shown in FIG. 9, a plurality of droplet discharge heads 112 are arranged in a direction perpendicular to the conveying direction of the sheet material P so as to have a long shape wider than the maximum width of the sheet material P. There are provided (four in this embodiment) droplet discharge units 98. Each droplet discharge unit 98 includes a plurality of ejectors 26 that discharge ink droplets, a first main channel 38 and a first branch channel 34 that supply ink to each ejector 26, and ink discharged from each ejector 26. The second branch flow path 36 and the second main flow path 40 into which the gas flows are configured.

  The droplet discharge unit 98 is a droplet discharge unit 98A, a droplet discharge unit 98B, a droplet discharge unit 98C, and a droplet discharge unit 98D in order from the left side shown in FIG. In this case, the droplet discharge unit 98 is described.

  Further, the droplet discharge head 112 has a liquid tank 154 in which ink supplied to each droplet discharge unit 98 is stored, and a long shape that supplies the ink in the liquid tank 154 to the droplet discharge unit 98. A first common flow path 156 and a long second common flow path 158 for collecting the ink discharged from the droplet discharge unit 98 and returning it to the liquid tank 154 are provided. Specifically, the first common flow path 156 supplies ink to the droplet discharge unit 98 through the filter 156A constituting the first supply flow path, and the second common flow path 158 constitutes the second common flow path 158. Ink is collected through a filter 158A.

  The first common flow path 156 is provided with a circulation pump 160 as a circulation means, and the second common flow path 158 is provided with a circulation pump 161. By operating the circulation pumps 160 and 161, the liquid tank The ink stored in 154 is supplied to each droplet discharge unit 98 through the first common channel 156, and the ink discharged from each droplet discharge unit 98 is returned to the liquid tank 154 through the second common channel 158. be able to. In this way, ink is circulated between the plurality of droplet discharge units 98 and the liquid tank 154.

(Action / Effect)
Here, the inventor of the present application determines the circulation amount of the ink flowing to each ejector 26 by using the first fluid channel 92 including the first branch channel 34 and the first main channel 38, the second branch channel 36, and the like. The calculation was made based on the flow resistance of the second fluid flow path 94, the first common flow path 156, and the second common flow path 158 composed of the second main flow path 40.

  As shown in FIG. 9, as in the first embodiment, each droplet discharge unit 98 is divided into three groups of range A, range B, and range C according to the ink circulation amount.

  Then, as shown in FIG. 10A, the circulation amount of the ejector 26 arranged in the range C of the droplet discharge unit 98D (the droplet discharge unit 98 arranged on the rightmost side) is the largest, and the flow rate rank is 6. there were. On the other hand, the circulation amount of the ejector 26 arranged in the range A of the droplet discharge unit 98A (the droplet discharge unit 98 arranged on the leftmost side) was the smallest and the flow rate rank 1. The flow rate rank 1 is the least circulating amount, and the rank is increased to 2 and 3, so that the circulation amount increases, and can be classified into 6 groups of flow rate ranks 1, 2, 3, 4, 5, and 6. It was.

  Then, as shown in FIG. 10 (B), the drive control unit 88 applied different preliminary waveforms defining the pulse width, voltage, and frequency to the drive elements 52 of each ejector 26 for each flow rate rank. As a result, the droplet speed of the ink ejected from the nozzle was stabilized.

  Thus, the drive control unit 88 sets the circulation amount calculated based on the flow resistances of the first common flow path 156, the first fluid flow path 92, the second common flow path 158, and the second fluid flow path 94. Based on this, different preliminary waveforms are applied to the drive element 52. As a result, it is possible to suppress an increase in power consumption, suppress an increase in the viscosity of the ink discharged from the nozzle 30, and further stably discharge the ink from the nozzle 30.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It is clear to the contractor. For example, in the above-described embodiment, the preliminary waveform is applied only once before the main waveform for ejecting ink. However, the preliminary waveform may be applied continuously after the nozzles eject ink droplets last.

  In the above-described embodiment, the droplet discharge head 112 includes the four droplet discharge units 98. However, the number of droplet discharge units 112 is not four, but may be other numbers such as eight.

  Further, the present invention has been described using the circulation type in which the liquid flowing into the second fluid flow path is returned to the liquid tank and reused in order to eliminate wasteful consumption of ink, but is limited to the circulation type. However, the present invention can also be implemented in a configuration in which the liquid flowing into the second fluid flow path is discarded as it is.

It is the schematic diagram which showed the droplet discharge unit which concerns on 1st Embodiment of this invention. It is sectional drawing which showed the ejector employ | adopted as the droplet discharge unit which concerns on 1st Embodiment of this invention. (A) It is the comparative example of the droplet discharge unit which concerns on 1st Embodiment of this invention, Comprising: It is drawing which showed the droplet speed at the time of applying the same preliminary waveform to the ejector of each group. (B) It is drawing which showed the droplet speed at the time of applying a different preliminary waveform to the ejector of each group of the droplet discharge unit which concerns on 1st Embodiment of this invention. (A), (B), and (C) are drawings showing preliminary waveforms applied to the drive element of the droplet discharge unit according to the first embodiment of the present invention. 1 is a perspective view showing an ink jet recording apparatus employing a droplet discharge unit according to a first embodiment of the present invention. It is the schematic diagram which showed the droplet discharge unit which concerns on 2nd Embodiment of this invention. (A) It is a comparative example of the droplet discharge unit which concerns on 2nd Embodiment of this invention, Comprising: It is drawing which showed the droplet speed at the time of applying the same preliminary waveform to the ejector of each group. (B) It is drawing which showed the droplet speed at the time of applying a different preliminary waveform to the ejector of each group of the droplet discharge unit which concerns on 2nd Embodiment of this invention. (A) (B) (C) (D) (E) It is drawing which showed the preliminary | backup waveform applied to the drive element of the droplet discharge unit based on 2nd Embodiment of this invention. It is the schematic diagram which showed the droplet discharge head which concerns on 3rd Embodiment of this invention. (A) Drawing which divided the ejector provided in the droplet discharge head concerning a 3rd embodiment of the present invention according to circulation amount (B) It was provided in the droplet discharge head concerning a 3rd embodiment of the present invention It is the figure which showed the parameter of the preliminary waveform applied to an ejector. FIG. 5 is a schematic configuration diagram illustrating an inkjet recording apparatus that employs a droplet discharge head according to a third embodiment of the present invention.

Explanation of symbols

10 Inkjet recording device (image forming device)
12 Droplet discharge unit 26 Ejector 30 Nozzle 42 Liquid tank 48 Circulation pump (circulation means)
51 Actuator 52 Drive Element 88 Drive Control Unit 92 First Fluid Channel 94 Second Fluid Channel 96 Liquid Tank 98 Droplet Discharge Unit 110 Inkjet Recording Device (Image Forming Device)
112 Liquid droplet ejection head 156 First common flow path 158 Second common flow path 160 Circulation pump (circulation means)

Claims (10)

  1. A plurality of ejectors having a nozzle that discharges droplets, a pressure chamber that communicates with the nozzle via a communication path, and an actuator that applies pressure to the liquid in the pressure chamber;
    A first fluid flow path through which a liquid supplied to the pressure chamber of the ejector flows;
    A second fluid channel through which the liquid supplied from the first fluid channel to the pressure chamber flows through the communication path;
    Circulating means for circulating liquid from the ejector to the ejector through the first fluid flow path and through the second fluid flow path;
    Based on the circulation amount of the liquid circulating through each of the ejectors, a preliminary waveform for stirring the liquid in the vicinity of the nozzle is reduced, and the voltage applied to the actuator is reduced with respect to the main waveform for discharging droplets from the nozzle. And a drive control unit for changing the application time,
    The drive control unit is a droplet discharge unit that applies the preliminary waveform to the actuator so that the application time is longer when the circulation amount is small than when the circulation amount is large .
  2.   2. The droplet discharge unit according to claim 1, wherein the circulation amount is calculated based on a channel resistance of the first fluid channel and the second fluid channel.
  3.   3. The droplet discharge unit according to claim 1, wherein the drive control unit applies different preliminary waveforms to the actuators of the ejectors divided into a plurality of groups based on the circulation amount. 4. .
  4. The drive control unit, the first fluid flow path and the flow path resistance of the second fluid flow path, and the preliminary waveform different to the actuator based on the circulation amount calculated by the viscosity of the liquid flowing through the ejector The droplet discharge unit according to claim 1, wherein the droplet discharge unit is applied.
  5.   An image forming apparatus comprising the droplet discharge unit according to claim 1.
  6. A plurality of ejectors having a nozzle that discharges droplets, a pressure chamber that communicates with the nozzle through a communication path, and an actuator that applies pressure to the liquid in the pressure chamber;
    A first fluid flow path through which a liquid supplied to the pressure chamber of the ejector flows;
    A second fluid channel through which the liquid supplied from the first fluid channel to the pressure chamber flows through the communication path;
    A plurality of droplet discharge units comprising:
    A first common flow path for supplying a liquid to the first fluid flow path of each of the droplet discharge units;
    A second common channel through which the liquid supplied from the first common channel to the droplet discharge unit through the first fluid channel flows through the second fluid channel of the droplet discharge unit;
    Circulating means for circulating liquid from the droplet discharge unit through the second common channel to the droplet discharge unit through the first common channel;
    Based on the circulation amount of the liquid circulating through each of the ejectors, a preliminary waveform for stirring the liquid in the vicinity of the nozzle is reduced, and the voltage applied to the actuator is reduced with respect to the main waveform for discharging droplets from the nozzle. And a drive control unit for changing the application time,
    The drive control unit is a droplet discharge unit that applies the preliminary waveform to the actuator so that the application time is longer when the circulation amount is small than when the circulation amount is large .
  7.   The circulation amount is calculated based on flow resistances of the first fluid flow path, the second fluid flow path, the first common flow path, and the second common flow path. The droplet discharge head described in 1.
  8.   8. The droplet discharge head according to claim 6, wherein the drive control unit applies different preliminary waveforms to the actuators of the ejectors divided into a plurality of groups based on the circulation amount. .
  9. The drive control unit includes the actuator based on the circulation amount calculated by the circulation amount calculated by the flow resistance of the first fluid channel and the second fluid channel and the viscosity of the liquid flowing through the ejector. The liquid droplet ejection head according to claim 6, wherein different preliminary waveforms are applied to the liquid crystal.
  10.   An image forming apparatus comprising the liquid droplet ejection head according to claim 6.
JP2007324655A 2007-12-17 2007-12-17 Droplet discharge unit, droplet discharge head, and image forming apparatus having the same Active JP4968040B2 (en)

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