JP5560749B2 - Fluid ejecting apparatus and cleaning method - Google Patents

Description

  The present invention relates to a fluid ejecting apparatus and a cleaning method for the fluid ejecting apparatus.

  2. Description of the Related Art Conventionally, ink jet printers are widely known as fluid ejecting apparatuses that eject a fluid onto a medium. This printer performs printing processing on a medium by ejecting ink (fluid) from nozzles formed in a fluid ejecting head.

  In such a printer, dot missing may occur in a printed image by performing ejection in a nozzle missing state in which bubbles are mixed in the nozzle. In order to suppress the occurrence of defective printing due to missing dots, there has been a printer that performs cleaning that discharges bubbles in the nozzle together with ink (for example, Patent Document 1).

JP 2007-152725 A

  In such cleaning, a large amount of ink is consumed in order to discharge bubbles, and in Patent Document 1, the amount of ink supplied is changed according to the degree of printing failure. However, since a considerable amount of ink is still consumed with cleaning, further reduction of ink consumption has been a problem.

  The present invention has been made in view of these problems, and an object thereof is to provide a fluid ejecting apparatus and a cleaning method capable of discharging bubbles while suppressing consumption of fluid.

In order to achieve the above object, a fluid ejecting apparatus of the present invention includes a fluid ejecting head provided with a plurality of nozzles for ejecting fluid, a fluid supply path for supplying the fluid toward the fluid ejecting head, A pressure applying mechanism for expanding the fluid from the nozzle by pressurizing the fluid in the fluid supply path and performing pressure reduction in a state in which the fluid is expanded from the nozzle in accordance with the pressurization; The pressure application mechanism is a mechanism that performs the pressurization by decreasing the volume of the fluid supply path and performs the pressure reduction by increasing the volume of the fluid supply path, and the pressure application mechanism The volume of the fluid supply path that is increased due to the pressure reduction is smaller than the volume of the fluid supply path that is decreased due to the pressurization .

According to this configuration, the pressure applying mechanism pressurizes the fluid in the fluid supply path, so that a part of the fluid is expanded from the nozzle, and bubbles mixed in the expanded portion of the fluid are removed. It can be pushed out to the atmosphere side outside the nozzle opening. In addition, when the pressure application mechanism performs pressure reduction continuously with pressurization, the fluid that is swollen from the nozzle accompanying pressurization is placed in the fluid ejecting head so as not to be wasted due to dropping from the nozzle opening or the like. Can be pulled back. Therefore, bubbles can be discharged while suppressing the consumption of fluid.
Note that the pressure applying mechanism reduces the volume of the fluid supply path, thereby pushing out the fluid corresponding to the reduced volume and spreading the pressure to the nozzle side. Further, since the pressure reduction is performed by increasing the volume of the fluid supply path, the pressure reduction can be performed continuously with the pressure by returning the volume reduced for the pressurization. When air bubbles are discharged from the nozzle in accordance with pressurization, a gap is generated in the nozzle, and the volume of the fluid supply path that is increased for pressure reduction is reduced by the pressure of the fluid supply path that is decreased for pressurization. Since it is smaller than the volume, it is possible to suppress the occurrence of nozzle omission due to the gap.

In the fluid ejecting apparatus according to the aspect of the invention, in the pressure applying mechanism, the depressurization time for performing the depressurization is longer than the pressurization time for performing the pressurization.
According to this configuration, it is possible to suppress the drawing of bubbles from the nozzle opening by performing the pressurization in a short time to secure the bubble discharge property and making the decompression time longer than the pressurization time.

  In the fluid ejecting apparatus according to the aspect of the invention, the fluid ejecting head includes a plurality of fluid ejecting heads, stores the fluid supplied via the fluid supply path, and supplies the stored fluid to the plurality of fluid ejecting heads. A chamber is further provided.

  According to this configuration, the meniscus of the nozzle can be uniformly adjusted by adjusting the back pressure of each nozzle in the fluid storage chamber. Further, since the pressure applying mechanism is provided on the upstream side of the fluid storage chamber in the fluid flow path, the configuration is not complicated even when the number of fluid ejecting heads is increased.

In the fluid ejecting apparatus according to the aspect of the invention, in the pressure applying mechanism, the pressurization time for performing the pressurization is 0.025 seconds to 0.5 seconds.
According to this configuration, the pressurizing time for the pressure applying mechanism to pressurize is as short as 0.025 seconds to 0.5 seconds, so that bubbles attached to the inner wall of the nozzle are peeled off and discharged. Can do.
The fluid ejecting apparatus of the present invention further includes a valve for closing the fluid supply path upstream of the pressure applying mechanism in the fluid supply path.

In order to achieve the above object, a cleaning method of the present invention includes a fluid ejecting head provided with a plurality of nozzles ejecting fluid, a fluid supply path for supplying the fluid toward the fluid ejecting head, and the fluid A cleaning method for a fluid ejecting apparatus having a pressure applying mechanism capable of continuously executing pressurization and pressure reduction on the fluid in a supply path , wherein the pressure applying mechanism reduces the volume of the fluid supply path. The pressurizing step of causing the fluid to bulge from the nozzle by performing the pressurization, and after the pressurizing step, in a state where the fluid bulges from the nozzle, the pressure applying mechanism is connected to the fluid supply path. and a decompression step of performing the decompression by increasing the volume, the volume of the fluid supply passage is increased for the vacuum in the vacuum process, for the pressure in the pressurizing step Less than the volume of said fluid supply path lack causes.

  According to this configuration, it is possible to obtain the same effect as that of the fluid ejecting apparatus.

1 is a schematic front view illustrating a schematic configuration of an ink jet printer according to a first embodiment. The bottom view which shows the structure of a line head. FIG. 3 is a cross-sectional view illustrating a schematic configuration in a fluid ejecting head. Sectional drawing which shows schematic structure of a capping apparatus. Sectional drawing which shows schematic structure of a wiping apparatus. It is sectional drawing for demonstrating the structure and effect | action of a pressure provision mechanism, (a) is before pressurization, (b) shows the time of pressurization. It is sectional drawing for demonstrating ink non-supply cleaning, (a) before pressurization, (b) at the time of pressurization, (c) at the time of pressure reduction, (d) shows after stationary. The graph which shows the relationship between pressurization time and pressure reduction time. The table | surface which shows the flow-path conditions 1 of the ink jet type printer in 1st Embodiment. (A) is a table | surface which shows the range of the pressurization ink amount in flow-path condition 1, (b) is a table | surface which shows the range of the pressurization time and pressure reduction time in flow-path condition 1. The model front view which shows schematic structure of the ink jet type printer in 2nd Embodiment. It is sectional drawing for demonstrating the structure and effect | action of a differential pressure | voltage valve, (a) at the time of valve closing, (b) shows the time of valve opening. (A) is a table | surface which shows the range of the pressurization ink amount in the flow path conditions 2 of the inkjet type printer in 2nd Embodiment, (b) is a table | surface which shows the range of the pressurization time in the flow path conditions 2, and the pressure reduction time. Sectional drawing which shows the modification of a structure of a pressure provision mechanism.

(First embodiment)
A first embodiment in which the present invention is embodied in an ink jet printer (hereinafter simply referred to as a “printer”), which is a type of fluid ejecting apparatus, will be described below with reference to FIGS. In the following description, when referring to “front-rear direction”, “left-right direction”, and “up-down direction”, the front-rear direction, the left-right direction, and the up-down direction indicated by arrows in the drawings are respectively shown.

  As shown in FIG. 1, the printer 11 includes a transport unit 12 that transports a sheet P as a medium, a line head 13 that performs a printing process on the sheet P, and an ink supply unit that supplies ink as a fluid to the line head 13. 14 and a maintenance unit 15.

  The transport unit 12 includes a pair of paper feed rollers 16, an endless transport belt 17, a drive roller 18, a driven roller 19, a drive motor 20 connected to the drive roller 18, and a pair of paper discharge rollers 21. It has. The conveying belt 17 is wound around the driving roller 18 and the driven roller 19, and rotates when the driving roller 18 rotates in the clockwise direction in FIG. The paper P is transported along the transport direction X by the paper feed roller 16, the transport belt 17, and the paper discharge roller 21. A plurality of (for example, two) conveyor belts 17 are provided so as to support at least both ends in the width direction Y (front-rear direction) of the paper P, and a maintenance unit is provided between the conveyor belts 17 arranged in the front-rear direction. 15 is arranged.

  The line head 13 includes a base portion 23 and a fluid ejecting head 24 supported by the base portion 23. As shown in FIG. 2, the fluid ejecting heads 24 are arranged in a staggered pattern so as to form two rows of lines extending along the width direction Y of the paper P. The first row located on the upstream side (left side) in the transport direction X is composed of four fluid ejection heads 24 arranged along the width direction Y, and is located on the downstream side (right side) in the transport direction X. The second row includes four fluid ejecting heads 24 arranged along the width direction Y.

  Each fluid ejecting head 24 is provided with a plurality of nozzles 25 for ejecting ink. Then, two nozzle rows N extending along the width direction Y are formed by the nozzle openings 25 a of the plurality of nozzles 25 on the nozzle forming surface 24 a formed from the lower surface (bottom surface) of the fluid ejecting head 24. As shown in the partially enlarged view of FIG. 2, in the two nozzle rows N, the nozzle openings 25a are arranged in a staggered manner so that the arrangement interval along the width direction Y is shifted by ½ pixel. In the first and second fluid ejecting heads 24, when projected in the transport direction X, at least one nozzle 25 at both ends overlaps or the nozzles 25 at both ends are continuous at a nozzle pitch. It has become.

  For this reason, the printer 11 can perform printing in the maximum paper width range even when the line head 13 is fixed. In the present embodiment, one fluid ejecting head 24 corresponds to 1.1 inches of paper, and the eight fluid ejecting heads 24 have an A4 size (297 mm long × 210 mm wide) width (about 8.3 inches). It comes to cover. One nozzle row N is composed of 330 nozzles 25. Therefore, one line head 13 is arranged along the width direction Y 8 (the number of fluid ejecting heads 24) × 2 (the number of nozzle rows N) × 330 (the number of nozzles 25 constituting the nozzle row N) = 5280. The nozzles 25 are provided.

  The line head 13 and the ink supply unit 14 are provided for each color, for example, when four colors of cyan (C), magenta (M), yellow (Y), and black (K) are printed. (FIGS. 1 and 2 show one by one for simplicity). Then, by printing four color ink droplets on the conveyed paper P from the four line heads 13, a printing process with a resolution of 600 dpi is possible.

  As shown in FIG. 1, the ink supply unit 14 includes an ink cartridge 26 that contains ink, an ink supply tube 27 that forms a fluid supply path that supplies ink from the ink cartridge 26 toward the fluid ejecting head 24, And a pressurizing pump 28 for supplying the ink under pressure. The ink cartridge 26 is connected to the ink supply tube 27 by being detachably mounted on a cartridge holder (not shown). A pressure applying mechanism 29 is provided in the middle of the ink supply tube 27.

  A common ink chamber 30 that temporarily stores ink supplied from the ink cartridge 26 through the ink supply tube 27 is provided in the base portion 23 of the line head 13. A plurality of branch flow paths 31 corresponding to each fluid ejecting head 24 are connected to the common ink chamber 30. The ink stored in the common ink chamber 30 is supplied to the plurality of fluid ejecting heads 24 through the branch flow path 31.

  As shown in FIG. 3, the fluid ejecting head 24 includes a flow path forming member 32, a vibration plate 33, a flow path forming member 34, and a nozzle plate 35 that are stacked in the vertical direction. A branch channel 31 that communicates with the common ink chamber 30, a reservoir 36, and a storage chamber 37 are formed in the channel forming member 32. The diaphragm 33 is provided with a communication hole 38 at a position corresponding to the reservoir 36. A cavity 39 that communicates with the reservoir 36 through the communication hole 38 is formed in the flow path forming member 34.

  A piezoelectric element 40 is disposed on the upper surface side of the diaphragm 33 at a position above the cavity 39. A nozzle 25 communicating with the cavity 39 is formed in the nozzle plate 35. That is, the ink distributed from the common ink chamber 30 to each fluid ejecting head 24 through the branch flow path 31 is stored in the reservoir 36 and supplied from the reservoir 36 to each nozzle 25 through the communication hole 38 and the cavity 39.

  The diaphragm 33 is attached so as to vibrate in the vertical direction, and the piezoelectric element 40 expands and contracts in response to the drive signal, thereby vibrating the diaphragm 33 in the vertical direction. Further, when the vibration plate 33 vibrates in the vertical direction, the volume of the cavity 39 is expanded and contracted. When the volume of the cavity 39 is reduced, the ink in the cavity 39 is ejected from the nozzle 25 as an ink droplet Fb. The nozzle forming surface 24 a of the fluid ejecting head 24 is configured by the lower surface (bottom surface) of the nozzle plate 35. In this embodiment, the nozzle opening 25a has a diameter of about 20 micrometers, and the thickness of the nozzle plate 35 in the vertical direction is about 100 micrometers.

  Here, the ink cartridge 26 is provided at a position lower than the line head 13. Therefore, the region (ink flow path) in the fluid ejecting head 24 has a negative pressure of about −1 kPa due to a water head difference. This negative pressure is to prevent ink from dripping from the nozzle 25 and to form a concave meniscus in the nozzle 25 to stabilize the ejection operation.

Next, the maintenance unit 15 will be described.
The maintenance unit 15 includes a capping device 41 (see FIG. 4) for capping the nozzle forming surface 24a of the fluid ejecting head 24, and a wiping device 42 (see FIG. 5) for wiping the nozzle forming surface 24a. Yes. The capping device 41 and the wiping device 42 may be provided for each fluid ejecting head 24, or a plurality of fluid ejecting heads 24 may be capped or wiped simultaneously.

  The capping device 41 is used for capping to prevent the nozzle 25 from drying, and performs suction cleaning for discharging bubbles, thickened ink, and the like by sucking ink in the ink cartridge 26 from the nozzle 25. Used when. Further, the capping device 41 is also used to receive ink discharged from the nozzle 25 during pressure cleaning in which the ink in the ink cartridge 26 is discharged from the nozzle 25 by the pressure pump 28. On the other hand, the wiping device 42 is used when wiping is performed for wiping the nozzle forming surface 24 a to remove deposits such as paper dust and ink, and for adjusting the meniscus of the nozzle 25.

First, the capping device 41 will be described.
As shown in FIG. 4, the capping device 41 includes a bottomed square box-shaped cap 43, an elevating mechanism 44 that raises and lowers the cap 43, and a suction mechanism 45. A rectangular frame-shaped sealing member 46 made of a flexible material is provided on the entire upper surface of the peripheral wall of the cap 43, and a discharge pipe 47 is provided on the bottom wall of the cap 43 so as to protrude downward.

  One end of a discharge tube 48 made of a flexible material constituting the suction mechanism 45 is connected to the discharge pipe 47. The other end side of the discharge tube 48 is inserted into a waste ink tank 49. In the waste ink tank 49, a waste ink absorber 50 made of a porous member is accommodated.

  Between the cap 43 and the waste ink tank 49, a tube pump 51 constituting the suction mechanism 45 is disposed. The tube pump 51 includes a cylindrical case 52, a pump wheel 53 having a circular shape in plan view, a wheel shaft 54, and a pair of pressing rollers 55. The pump wheel 53 is accommodated in the case 52 so as to be rotatable around a wheel shaft 54 provided at the axial center of the case 52. Further, the intermediate portion of the discharge tube 48 is accommodated in the case 52 along the inner peripheral wall of the case 52.

  A pair of roller guide grooves 56 having an arc shape are formed in the pump wheel 53 so as to face each other with the wheel shaft 54 interposed therebetween. Each roller guide groove 56 has one end located on the inner peripheral side of the pump wheel 53 and the other end located on the outer peripheral side of the pump wheel 53. That is, both roller guide grooves 56 extend so as to gradually move away from the wheel shaft 54 from one end to the other end. Further, the pair of pressing rollers 55 is inserted and supported in both roller guide grooves 56 via a rotation shaft 57. Both the rotating shafts 57 are slidable in the roller guide grooves 56, respectively.

  When the pump wheel 53 is rotated in the forward direction (clockwise direction indicated by an arrow in FIG. 4), the pressing roller 55 moves forward to the other end side of the roller guide groove 56 (the outer peripheral side of the pump wheel 53). The middle portion of the discharge tube 48 rotates while being crushed sequentially from the upstream side to the downstream side. By this rotation, the inside of the discharge tube 48 upstream from the tube pump 51 is decompressed.

  Further, when the pump wheel 53 is rotated in the reverse direction (counterclockwise direction in FIG. 4), the pressing roller 55 moves in the backward direction to one end side of the roller guide groove 56 (inner peripheral side of the pump wheel 53). By this movement, both the pressing rollers 55 are in light contact with the intermediate portion of the discharge tube 48, and the reduced pressure state inside the discharge tube 48 is eliminated.

  The elevating mechanism 44 includes a cam member 58 that contacts the cap 43 from below, a motor 59 for rotating the cam member 58, and a power transmission mechanism 60. When the motor 59 is driven in the forward direction, the cam member 58 is rotated via the power transmission mechanism 60 so that the cap 43 comes into contact with the nozzle forming surface 24a.

  Accordingly, when the pump wheel 53 is driven in the positive direction with the cap 43 in contact with the nozzle forming surface 24a, a negative pressure is generated in the space region R surrounded by the cap 43 and the nozzle forming surface 24a. Thereby, the suction cleaning in which the ink is discharged from the nozzle 25 is executed. When the pump wheel 53 is driven in the reverse direction, the negative pressure in the space region R is eliminated. Thereafter, when the motor 59 of the elevating mechanism 44 is driven in the reverse direction, the cap 43 descends and retracts from the paper P conveyance path.

Next, the wiping device 42 will be described.
As shown in FIG. 5, the wiping device 42 includes a wiping mechanism 61 and a lifting mechanism 62 that lifts and lowers the wiping mechanism 61.

  The wiping mechanism 61 includes a holder 63, a lead screw 64 installed on the holder 63 so as to extend in the front-rear direction, a motor 65 for rotating the lead screw 64, a support member 66, and an elastic body such as rubber. And a plate-like wiper 67 made of The wiper 67 is supported in a manner standing on the support member 66, and the support member 66 is supported by a lead screw 64. A storage recess 66 a is formed on the upper surface side of the support member 66.

  The elevating mechanism 62 includes a cam member 68 that contacts the holder 63 of the wiping mechanism 61 from below, a motor 69 for rotating the cam member 68, and a power transmission mechanism 70. When the motor 69 is driven in the forward direction, the cam member 68 is rotated via the power transmission mechanism 70, and the wiping mechanism 61 rises to a position where the wiper 67 contacts the nozzle forming surface 24a. ing.

  When the motor 65 is driven in the forward direction, the lead screw 64 rotates in the forward direction, and the wiper 67 moves along the front-rear direction together with the support member 66 in sliding contact with the nozzle forming surface 24a. Thereby, the wiping which cleans the nozzle formation surface 24a by wiping is performed. At this time, the ink or paper powder wiped from the nozzle forming surface 24a flows down through the wiper 67 and is stored in the storage recess 66a.

Next, the pressure applying mechanism 29 will be described.
As shown in FIG. 6, the pressure applying mechanism 29 has a flow path forming member 71 having a regularity. A connecting portion 72 connected to the upstream ink supply tube 27 is provided at the left end of the flow path forming member 71, while a connecting portion connected to the downstream ink supply tube 27 is provided at the right end of the flow path forming member 71. 73 is provided. Further, a concave portion 71 a having a circular shape in plan view is formed on the upper surface side of the flow path forming member 71. In the connection portion 72, an inflow path 72a that connects the upstream ink supply tube 27 and the inside of the recess 71a is formed. On the other hand, in the connection portion 73, an outflow path 73a that connects the downstream ink supply tube 27 and the inside of the recess 71a is formed.

  On the upper surface side of the flow path forming member 71, a flexible film member 74 is fixed in a bent state so as to seal the opening of the recess 71a. In addition, a disc-shaped pressing plate 74a having an area smaller than the opening area of the recess 71a is fixed to a substantially central portion on the outer surface side of the film member 74. And the pressure chamber 75 is enclosed and formed by the film member 74 and the recessed part 71a. The pressure chamber 75 constitutes a part of the fluid supply path by communicating with the ink supply tube 27 through the inflow path 72a and the outflow path 73a.

  In the pressure chamber 75, a biasing member 76 that biases the film member 74 in a direction of expanding the internal volume of the pressure chamber 75 is disposed. The urging member 76 can be composed of, for example, a coil spring or a leaf spring. A cam member 77 that contacts the pressing plate 74a is disposed above the pressing plate 74a. The cam member 77 is supported via a rotation shaft 78 and rotates together with the rotation shaft 78 as the motor 79 is driven.

  Accordingly, when the motor 79 is driven in the forward direction in the state shown in FIG. 6A, the cam member 77 rotates counterclockwise in FIG. 6 against the urging force of the urging member 76. As a result, the film member 74 is displaced in a direction to decrease the internal volume of the pressure chamber 75 as shown in FIG. 6B, and the ink in the ink supply tube 27 is pressurized by the ink pushed out from the pressure chamber 75. The Further, when the motor 79 is driven in the reverse direction in the state shown in FIG. 6B, the cam member 77 rotates in the clockwise direction in FIG. As a result, the urging force of the urging member 76 displaces the film member 74 in the direction of increasing the internal volume of the pressure chamber 75, and the ink supply tube 27 is decompressed by the ink drawn into the pressure chamber 75.

Next, a maintenance operation in the printer 11 will be described.
In the printer 11, when the ink cartridge 26 is replaced, bubbles are mixed in the ink supply tube 27 to cause missing dots, or the ink is thickened because the power is turned off and the nozzle 25 is clogged. May occur. In order to suppress a decrease in print quality due to such dot omission and clogging, the printer 11 uses the capping device 41 to perform suction cleaning and pressure cleaning. Hereinafter, cleaning in which ink is discharged from the nozzles 25 while supplying ink in the ink cartridge 26 in this manner is referred to as “ink supply cleaning”.

  When paper dust or the like adheres to the nozzle forming surface 24a by the printing process, the wiping device 42 wipes the nozzle forming surface 24a. After the ink supply cleaning, the discharged ink adheres to the nozzle forming surface 24a or a convex meniscus is formed in the nozzle opening 25a. Therefore, wiping is performed immediately after the ink supply cleaning.

  However, when such wiping is performed, the wiper 67 pushes air into the nozzle 25, and fine bubbles may be generated in the nozzle 25. Such bubbles are much smaller than bubbles mixed in when the ink cartridge 26 is replaced, and often remain near the nozzles 25. Therefore, in the printer 11, the ink non-supply cleaning by the pressure applying mechanism 29 is executed in order to discharge minute bubbles near the nozzle 25.

Next, ink non-supply cleaning by the pressure applying mechanism 29 will be described in detail.
Ink non-supply cleaning is performed in a pressurizing step in which the pressure applying mechanism 29 pressurizes and bulges ink from the nozzle 25, and in a state where the ink bulges from the nozzle 25 due to pressurization after the pressurizing step. The pressure applying mechanism 29 includes a pressure reducing process for reducing pressure. That is, in the pressurizing step, the pressure applying mechanism 29 pushes the ink in the pressure chamber 75 at a stroke to propagate the pressure into the nozzle 25 and draws bubbles adhering to the inner wall of the nozzle 25 as shown in FIG. Peel off. Then, as shown in FIG. 7B, the bubbles are pushed out from the nozzle 25 to the atmosphere side outside the nozzle opening 25a.

  In the decompression step, the pressure applying mechanism 29 increases the volume of the pressure chamber 75, thereby pulling back the ink that has been pushed into the pressure chamber 75. As a result, before the ink droplet Fb is ejected or dropped (dropped) from the nozzle 25, the ink in a bulging state from the nozzle 25 is collected in the nozzle 25 as shown in FIG. . When the bubbles are discharged, a gap corresponding to the volume of the bubbles is generated in the nozzle 25, but when left for a short time, the ink in the common ink chamber 30 is caused to enter the nozzle 25 by capillary force as shown in FIG. To be replenished.

  By performing the pressurization and decompression of the ink non-supply cleaning repeatedly a plurality of times, bubbles that are difficult to be discharged can be gradually moved outward. For example, when pressurization and depressurization are repeated a plurality of times, not only the inside of the nozzle 25 but also the bubbles in the fluid ejecting head 24 and the common ink chamber 30 can be discharged. In addition, even when a gap is generated in the nozzle 25 as the bubbles are discharged, the liquid surface position of the nozzle 25 is gradually aligned by repeatedly performing pressurization and pressure reduction.

  In the decompression step, the volume decreased in the pressurization step may be returned to the original, or the volume increased for decompression may be made smaller than the volume decreased for pressurization. For example, when a relatively large bubble in the common ink chamber 30 is discharged by repeating pressurization and depressurization a plurality of times, there is a possibility that a nozzle omission occurs in which the entire nozzle 25 becomes a gap. When such nozzle omission occurs, it may be difficult to replenish ink by capillary force. Therefore, it is preferable to reduce the amount of ink drawn in, particularly at the time of final depressurization in which pressurization and depressurization are repeated a plurality of times.

  Here, as shown in FIG. 8, it is preferable that the depressurization time Td during which pressure is reduced in the depressurization step is set longer than the pressurization time Ta during which pressurization is performed in the pressurization step. Also, if the pressurization time Ta is too short, the ink droplet Fb is ejected by the propagating pressure and the ink is wasted, or the ink is pulled back before the air pressure is started and the bubbles are pushed out. There is a risk of getting lost. On the other hand, if the pressurization time Ta is too long, the flow rate of the ink becomes slow and the bubbles cannot be removed from the inner wall of the nozzle 25, or the ink cannot be pulled back due to the reduced pressure and the ink is consumed. There is a risk of getting lost.

  On the other hand, if the decompression time Td is too long, there is a risk that the ink will be consumed in the same time because the ink cannot be pulled back in time. Conversely, if the pressure reduction time Td is too short, air may be drawn from the outside of the nozzle 25 and bubbles may be generated.

  An appropriate pressurization time Ta for ensuring ejection of bubbles while suppressing ejection of the ink droplets Fb is a very short time, for example, 0.05 seconds to 0.5 seconds. On the other hand, if the pressure is reduced in such a short time, air is drawn in. Therefore, for the pressurization time Ta of 0.05 to 0.5 seconds, the pressurization time Ta <the depressurization time Td. preferable.

  In the present embodiment, pressurization and pressure reduction are performed by changing the volume of the pressure chamber 75 to such an extent that the ink droplet Fb is not ejected from the nozzle 25. Therefore, appropriate values for the amount of ink to be pushed out in accordance with the volume variation for pressurization (hereinafter referred to as “pressurized ink amount Vd”), pressurization time Ta, and decompression time Td are the nozzle 25 and the fluid. It fluctuates depending on flow path conditions such as the number of ejection heads 24 installed. Accordingly, the range of appropriate values for the pressurized ink amount Vd, the pressure time Ta, and the pressure reduction time Td and the flow path conditions will be described.

  As a flow path condition (hereinafter referred to as “flow path condition 1”) of the printer 11 of the present embodiment, as shown in FIG. 9, the ink cartridge 26 has an internal volume (region No. 1) of about 50 cc, and the ink cartridge 26. The internal volume (area No. 2) of the ink supply tube 27 from the pressure chamber 75 to the pressure chamber 75 is about 3.5 cc. Further, the variable volume (region No. 3) of the pressure chamber 75 is about 1.0 cc, the internal volume (region No. 4) of the ink supply tube 27 on the downstream side of the pressure chamber 75 is about 1.9 cc, and the contents of the common ink chamber 30. The product (region No. 5) is about 3.1 cc, and the total internal volume (region No. 6) of the eight fluid ejecting heads 24 is about 0.9 cc.

  FIG. 10A shows an appropriate range of the pressurized ink amount Vd when ink non-supply cleaning is performed under the flow path condition 1, and FIG. 10B shows an appropriate range of the pressurizing time Ta and the depressurizing time Td. .

  Regarding the pressurized ink amount Vd, it is preferable to pressurize by reducing the volume in the range of 0.22 cc ≦ Vd ≦ 0.62 cc out of the volume of about 1.0 cc of the pressure chamber 75. When 0.22 cc> Vd, there is a possibility that a pressure sufficient to discharge bubbles may not be obtained, and when 0.62 cc <Vd, there is a possibility that ink is consumed.

  Further, when 0.22 cc ≦ Vd ≦ 0.62 cc, the pressurization time Ta is 0.05 seconds ≦ Ta ≦ 0.5 seconds, and the decompression time Td is 0.09 seconds ≦ Td ≦ 0.7 seconds (however, Ta <Td) is preferred.

  Ink non-supply cleaning by the pressure applying mechanism 29 does not cause ink to adhere to the nozzle forming surface 24a after execution, and the meniscus of the nozzle 25 can be adjusted, so that wiping is performed as post-processing like ink supply cleaning. There is no need. In addition, the ink consumption can be reduced to zero and can be performed in a very short time.

According to the embodiment described above, the following effects can be obtained.
(1) When the pressure application mechanism 29 pressurizes the ink in the ink supply tube 27, a part of the ink is swelled from the nozzle 25, and bubbles mixed in the swelled part of the ink are removed. It can extrude to the atmosphere side which becomes the outer side of the nozzle opening 25a. Further, when the pressure application mechanism 29 continuously reduces the pressure, the fluid ejection is performed so that the ink swelled from the nozzle 25 due to the pressurization is not wasted by dropping from the nozzle opening 25a. It can be pulled back into the head 24. Therefore, according to the ink non-supply cleaning by the pressure applying mechanism 29, it is possible to discharge bubbles while suppressing ink consumption.

  (2) By performing pressurization in a short time to ensure the discharge of bubbles, and by making the decompression time Td longer than the pressurization time Ta, it is possible to suppress the entrainment of bubbles from the nozzle opening 25a.

  (3) Since the pressure applying mechanism 29 reduces the volume of the pressure chamber 75, the ink corresponding to the reduced volume can be pushed out and the pressure can be applied to the nozzle 25 side. Further, since the pressure reduction is performed by increasing the volume of the pressure chamber 75, the pressure reduction can be continuously performed with the pressure by returning the volume reduced for the pressurization.

  (4) When air bubbles are discharged from the nozzle 25 along with the pressurization, a gap is generated in the nozzle 25 correspondingly, but the pressure chamber 75 is increased in pressure for reducing the volume of the pressure chamber 75 for increasing pressure. By making it smaller than the volume of the chamber 75, it is possible to suppress the occurrence of nozzle omission due to the gap.

  (5) By adjusting the back pressure of each nozzle 25 in the common ink chamber 30, the meniscus of the nozzle 25 can be uniformly adjusted. For example, the flow of ink accompanying the pressurization or decompression of the ink non-supply cleaning is spilled into the nozzle 25 via the common ink chamber 30. Therefore, even when a gap is generated in one nozzle 25 from which bubbles are discharged, the liquid surface position is aligned with the other nozzles 25 by repeating pressurization and pressure reduction. Since the pressure applying mechanism 29 is provided upstream of the common ink chamber 30 in the ink flow path, the configuration is not complicated even when the number of fluid ejecting heads 24 is increased.

  (6) Since the pressurization time Ta during which the pressure applying mechanism 29 performs pressurization in the flow path condition 1 is as short as 0.05 seconds to 0.5 seconds, the bubbles adhering to the inner wall of the nozzle 25 are removed. It can be peeled off and discharged.

(Second Embodiment)
Next, 2nd Embodiment of this invention is described based on FIGS.
In the printer 11 according to the first embodiment, the areas No1 to No6 constituting the ink flow path communicate with each other, so that the ink pushed out from the pressure chamber 75 is not only the downstream areas No3 to No6 but also the upstream. It moves also to the area | region No1, No2 of the side. For this reason, the pressure reaching the nozzle 25 is weakened by the amount of the pressure spreading upstream. Therefore, in the second embodiment, a printer 11A capable of causing the extruded ink to flow only downstream will be described.

  As illustrated in FIG. 11, the printer 11 </ b> A according to the second embodiment includes an ink supply unit 14 </ b> A instead of the ink supply unit 14 of the printer 11. In the ink supply unit 14 </ b> A, the ink supply tube 27 is provided with a differential pressure valve 80 and an on-off valve 81.

The on-off valve 81 is a valve that can be arbitrarily opened and closed, and is provided immediately upstream of the pressure applying mechanism 29. As the on-off valve 81, an electromagnetic valve or a mechanically operated valve can be employed. When the ink non-supply cleaning is executed, the on- off valve 81 is closed, so that the ink pushed out from the pressure chamber 75 flows down only to the downstream side.

  The differential pressure valve 80 is a diaphragm-type self-sealing valve that opens and closes using the differential pressure between the atmospheric pressure and the ink pressure, and is disposed between the ink cartridge 26 and the open / close valve 81. In the printer 11 </ b> A, an ink cartridge 26 (a cartridge holder (not shown)) is provided at a position higher than the line head 13. For this reason, the pressure inside the fluid ejecting head 24 is set to a negative pressure of about −1 kPa by the differential pressure valve 80.

  As shown in FIG. 12A, the differential pressure valve 80 has a flow path forming member 82 having a regular shape. A connecting portion 83 connected to the upstream ink supply tube 27 is provided at the left end of the flow path forming member 82, while a connecting portion connected to the downstream ink supply tube 27 is provided at the right end of the flow path forming member 82. 84 is provided. Further, a concave portion 82a having a circular shape in plan view is formed on the upper surface side of the flow path forming member 82, and a convex portion 82b having a truncated cone shape is formed at a position eccentric to the left from the center on the inner bottom surface of the concave portion 82a. One is formed. In addition, an inflow path 83a is formed in the connection portion 83 to communicate the upstream ink supply tube 27 and the recess 82a so that an opening into the recess 82a is formed at the upper end surface of the projection 82b. ing. On the other hand, in the connecting portion 84, an outflow path 84a that connects the downstream ink supply tube 27 and the inside of the recess 82a is formed.

  On the upper surface side of the flow path forming member 82, a flexible film member 85 is fixed in a bent state so as to seal the opening of the recess 82a. In addition, a disc-shaped pressing plate 86 having an area smaller than the opening area of the recess 82a is fixed to a substantially central portion on the inner surface facing the recess 82a of the film member 85. A pressure chamber 87 is surrounded by the film member 85 and the recess 82a.

  In the pressure chamber 87, a base portion 88, an arm member 89 supported by the base portion 88 so as to be tiltable, and one end side (left end side) of the arm member 89 are attached to the convex portion 82b side. An energizing spring 90 is accommodated. The arm member 89 normally receives the urging force of the urging spring 90, and one end side seals the opening of the inflow passage 83a provided on the upper end surface of the convex portion 82b, and the other end side (right end side) is pressed. The plate 86 is pushed upward. As a result, the film member 85 is deflected and displaced in the direction in which the internal volume of the pressure chamber 87 is enlarged, and the pressure in the pressure chamber 87 and the fluid ejecting head 24 located in the downstream area thereof becomes a negative pressure of about −1 kPa.

  Further, ink is supplied to the inflow passage 83a in a pressurized state by the pressurizing pump 28, and is always introduced into the pressure chamber 87 by one end side of the arm member 89 that receives the biasing force of the biasing spring 90. Inflow is suppressed. When ink is consumed by ejection or outflow from the nozzle 25, the negative pressure in the pressure chamber 87 increases, and the film member 85 resists the urging force of the urging spring 90 as shown in FIG. Thus, the pressure chamber 87 is deflected and displaced in the direction of decreasing the internal volume. Then, the other end side of the arm member 89 is pressed and tilted by the film member 85 via the pressing plate 86, and the one end side opens the opening of the inflow path 83a, so that the pressure chamber 87 is pressurized through the inflow path 83a. Ink flows in.

  When the negative pressure in the pressure chamber 87 decreases with the inflow of ink, the arm member 89 and the film member 85 are returned to their original positions by the biasing force of the biasing spring 90 again. Therefore, ink corresponding to the amount of consumption is supplied to the fluid ejecting head 24.

Next, ink non-supply cleaning in this embodiment will be described.
In the printer 11A, when the ink non-supply cleaning is executed, the on- off valve 81 is closed (hereinafter, this state is referred to as “flow path condition 2”). In the flow path condition 2, among the areas shown in FIG. 9, areas Nos. 3 to 6 excluding the areas Nos. 1 and 2 are affected ranges of pressurization and pressure reduction.

  FIG. 13A shows an appropriate range of the pressurized ink amount Vd when ink non-supply cleaning is performed under the flow path condition 2, and FIG. 13B shows an appropriate range of the pressurizing time Ta and the depressurizing time Td. .

With respect to the pressurized ink amount Vd, it is preferable to pressurize by reducing the volume in the range of 0.18 cc ≦ Vd ≦ 0.48 cc in the volume of about 1.0 cc of the pressure chamber 75. That is, since the pressure loss caused by the ink flowing to the regions No. 1 and No. 2 is eliminated, the bubbles can be discharged with the pressure ink amount Vd smaller than the flow channel condition 1 under the flow channel condition 2. In this case, since one line head 13 is provided with 5280 nozzles 25, the good bulging area of ink per nozzle is approximately 3.5 × 10 ⁻⁵ cc to 9.0 × 10. ^-5 cc. It has been confirmed that particularly good results can be obtained by applying pressure at Vd = 0.33 cc and Ta = 0.15 seconds and reducing pressure at Td = 0.35 seconds.

  Further, when 0.18 cc ≦ Vd ≦ 0.48 cc, the pressurization time Ta is 0.025 seconds ≦ Ta ≦ 0.2 seconds, and the decompression time Td is 0.1 seconds ≦ Td ≦ 0.5 seconds (however, Ta <Td) is preferred. That is, when the flow path conditions 1 and 2 are taken into account, it can be said that the pressurization time Ta during which the pressure application mechanism 29 performs pressurization in the pressurization step is preferably set to 0.025 seconds to 0.5 seconds.

According to the embodiment described above, in addition to the same effects as the above (1) to (5), the following effects can be obtained.
(6) In the flow path condition 2, the pressurization time Ta during which the pressure applying mechanism 29 pressurizes is a very short time from 0.025 seconds to 0.2 seconds, so that the bubbles adhering to the inner wall of the nozzle 25 are removed. It can be peeled off and discharged.

The above embodiment may be changed to another embodiment as described below.
The pressure applying mechanism 29 may be a pressure applying mechanism 29A configured as shown in FIG.
The pressure applying mechanism 29A includes a flow path forming member 91 having a regularity. A connecting portion 92 connected to the ink supply tube 27 is provided at the left end of the flow path forming member 91, while a connecting portion 93 connected to the ink supply tube 27 is provided at the right end of the flow path forming member 91. Further, a concave portion 91 a having a circular shape in plan view is formed on the upper surface side of the flow path forming member 91. An inflow path 92 a that connects the ink supply tube 27 and the recess 91 a is formed in the connection portion 92. On the other hand, in the connection portion 93, an outflow passage 93a that connects the ink supply tube 27 and the recess 91a is formed.

  A piston 94 is slidably accommodated in the recess 91 a of the flow path forming member 91. One end side (lower end side) of the piston 94 constitutes a disc-shaped movable portion 94a constituting one wall surface of the pressure chamber 75, and the other end side (upper end side) of the piston 94 constitutes a disc-shaped pressure receiving portion 94b. . The pressure chamber 75 is surrounded by the movable portion 94 a of the piston 94 and the recess 91 a of the flow path forming member 91.

  An urging member 76 made of a spring is disposed between the upper surface side of the flow path forming member 91 and the lower surface side of the pressure receiving portion 94b. Therefore, when the motor 79 is driven in the forward direction and the cam member 77 is rotated in the counterclockwise direction in the drawing, the movable portion 94a of the piston 94 is moved away from the rotating shaft 78. Then, the volume of the pressure chamber 75 decreases, and the ink in the ink supply tube 27 is pressurized by the ink pushed out from the pressure chamber 75. Further, when the motor 79 is driven in the reverse direction and the cam member 77 is rotated in the clockwise direction in the drawing, the movable portion 94a of the piston 94 is moved in the direction close to the rotating shaft 78 by the urging force of the urging member 76. To do. Then, the volume of the pressure chamber 75 increases, and the ink supply tube 27 is depressurized by the ink drawn into the pressure chamber 75.

  In the pressure applying mechanism 29, the piston 94 of the pressure applying mechanism 29A may be configured with a movable iron core, and a solenoid may be provided around the piston 94. In this case, the piston 94 made of a movable iron core can be moved by causing a current to flow through the solenoid to generate a magnetic field.

The pressure applying mechanism may include a piezoelectric element, and pressurization or decompression may be performed by changing the volume of the fluid supply path using the piezoelectric element.
The pressure may be applied by crushing the elastically deformable ink supply tube 27 with the cam member 77. In this case, the flow path forming member 71 need not be provided, so that the configuration can be simplified.

  The common ink chamber 30 is not provided, and for example, one end side (base end side) of the ink supply tube 27 is connected to the ink cartridge 26, while the other end side (tip end side) branches into a plurality of fluid ejecting heads 24. You may make it connect. In this case, the pressure applying mechanism 29 may be provided on the proximal end side, or the pressure applying mechanism 29 may be provided on the branched distal end side.

The pressure application mechanism may be provided between the common ink chamber 30 and the reservoir 36, or may be provided between the reservoir 36 and the cavity 39.
The liquid supply path may be configured from a rigid pipe line that is not easily elastically deformed. In this case, the pressure fluctuation accompanying pressure reduction in the pressurization step and pressure reduction in the pressure reduction step can be propagated into the nozzle 25 without being absorbed by the elastic deformation of the pipe line.

  ・ If the flow path condition or the fluid to be ejected is changed, the frictional resistance, flow path resistance, viscosity, etc. change, so the pressure ink amount Vd, pressurization time Ta, and decompression time Td are also changed to appropriate values. It is preferable to do this.

The number of fluid ejecting heads 24 and nozzles 25, the number of nozzle rows N, and the like can be arbitrarily set.
A non-removable ink tank may be adopted as the fluid container.

-You may implement | achieve as a full line type line head type printer provided with a long fluid ejection head, a lateral type printer, or a serial type printer.
In the above embodiment, the fluid ejecting apparatus is embodied as an ink jet printer, but a fluid ejecting apparatus that ejects or ejects fluid other than ink may be employed, and a minute amount of liquid droplets is ejected. The present invention can be applied to various liquid ejecting apparatuses including a liquid ejecting head to be used. In addition, a droplet means the state of the liquid discharged from the said liquid ejecting apparatus, and shall also include what pulls a tail in granular shape, tear shape, and thread shape. The liquid here may be any material that can be ejected by the liquid ejecting apparatus. For example, it may be in the state when the substance is in a liquid phase, such as a liquid state with high or low viscosity, sol, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals (metal melts ) And a liquid as one state of a substance, as well as a material in which particles of a functional material made of a solid such as a pigment or metal particles are dissolved, dispersed or mixed in a solvent. Further, representative examples of the liquid include ink and liquid crystal as described in the above embodiment. Here, the ink includes general water-based inks and oil-based inks, and various liquid compositions such as gel inks and hot melt inks. As a specific example of the liquid ejecting apparatus, for example, a liquid containing a material such as an electrode material or a color material used for manufacturing a liquid crystal display, an EL (electroluminescence) display, a surface emitting display, a color filter, or the like in a dispersed or dissolved state. It may be a liquid ejecting apparatus for ejecting, a liquid ejecting apparatus for ejecting a bio-organic material used for biochip manufacturing, a liquid ejecting apparatus for ejecting a liquid as a sample used as a precision pipette, a textile printing apparatus, a microdispenser, or the like. In addition, transparent resin liquids such as UV curable resin to form liquid injection devices that pinpoint lubricant oil onto precision machines such as watches and cameras, and micro hemispherical lenses (optical lenses) used in optical communication elements. A liquid ejecting apparatus that ejects a liquid onto the substrate or a liquid ejecting apparatus that ejects an etching solution such as an acid or an alkali to etch the substrate may be employed. The present invention can be applied to any one of these injection devices.

  DESCRIPTION OF SYMBOLS 11, 11A ... Printer as fluid ejecting apparatus, 24 ... Fluid ejecting head, 25 ... Nozzle, 27 ... Ink supply tube constituting fluid supply path, 29, 29A ... Pressure applying mechanism, 30 ... Common ink as fluid storage chamber Chamber, 75 ... pressure chamber constituting the fluid supply path, Ta ... pressurization time, Td ... pressure reduction time.

Claims (6)

A fluid ejecting head provided with a plurality of nozzles for ejecting fluid;
A fluid supply path for supplying the fluid toward the fluid ejecting head;
A pressure application mechanism that pressurizes the fluid in the fluid supply path to bulge the fluid from the nozzle and performs pressure reduction in a state in which the fluid bulges from the nozzle with the pressurization. It equipped with a door,
The pressure applying mechanism is a mechanism that performs the pressurization by decreasing the volume of the fluid supply path and performs the pressure reduction by increasing the volume of the fluid supply path,
In the pressure applying mechanism, the volume of the fluid supply path that is increased for the pressure reduction is smaller than the volume of the fluid supply path that is decreased for the pressurization . 2. The fluid ejecting apparatus according to claim 1, wherein in the pressure applying mechanism, a depressurization time for performing the depressurization is longer than a pressurization time for performing the pressurization. A plurality of the fluid ejecting heads are provided,
3. The fluid storage chamber according to claim 1, further comprising a fluid storage chamber for storing the fluid supplied through the fluid supply path and supplying the stored fluid to the plurality of fluid ejecting heads. The fluid ejecting apparatus according to the description. In the pressure applying mechanism, a fluid ejecting apparatus according to any one of claims 1 to 3, wherein the pressurization time for the pressure is 0.5 seconds 0.025 seconds . 5. The fluid ejection according to claim 1, further comprising a valve for closing the fluid supply path upstream of the pressure applying mechanism in the fluid supply path. apparatus. A fluid ejecting head provided with a plurality of nozzles for ejecting fluid, a fluid supply path for supplying the fluid toward the fluid ejecting head, and pressurization and decompression of the fluid in the fluid supply path are continuously performed And a method of cleaning a fluid ejection device having a pressure execution mechanism that can be executed in an automated manner,
The pressure application mechanism performs the pressurization by reducing the volume of the fluid supply path to bulge the fluid from the nozzle, and the fluid swells from the nozzle after the pressurization process. A pressure reducing step for reducing the pressure by increasing the volume of the fluid supply path in the discharged state ,
The cleaning method according to claim 1, wherein a volume of the fluid supply path that is increased for the pressure reduction in the pressure reducing process is smaller than a volume of the fluid supply path that is decreased for the pressurization in the pressurizing process.

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