JP2011161829A - Fluid ejecting apparatus and wiping method - Google Patents

Abstract

Provided are a fluid ejecting apparatus and a wiping method capable of suppressing the occurrence of missing dots while suppressing the consumption of fluid associated with wiping.
A printer is in sliding contact with a fluid ejecting head having a nozzle forming surface and a nozzle forming surface formed with a nozzle opening and a nozzle opening of the nozzle. The first sliding contact portion 44a that draws ink from the nozzle 25 and applies it to the nozzle forming surface 24a, and moves relative to the nozzle forming surface 24a after the ink is applied to the nozzle forming surface 24a by the first sliding contact portion 44a. The second sliding contact portion 44b for wiping the nozzle forming surface 24a by sliding contact with the ink, and pressurizing the ink in the fluid ejecting head 24 when drawing out the ink, while back pressure is applied when wiping the nozzle forming surface 24a. A pressure adjusting mechanism that performs pressure reduction so as to be lower than that during pressurization.
[Selection] Figure 5

Description

  The present invention relates to a fluid ejecting apparatus and a wiping method of 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 paper (medium) by ejecting ink (fluid) from nozzles formed in a fluid ejecting head.

  In such a printer, in order to stably eject ink droplets from the nozzle of the fluid ejecting head, the pressure of the ink in the fluid ejecting head, which is the back pressure of the liquid level in the nozzle, is always a negative pressure lower than atmospheric pressure. Had to keep on. In addition, such a printer includes a wiper for performing wiping to remove deposits (thickened ink, paper dust, etc.) adhering to the nozzle formation surface of the fluid ejecting head in which the nozzle openings are formed by sliding contact. There were some (for example, Patent Documents 1 and 2).

  In the printer of Patent Document 1, after the front surface of the wiper comes into sliding contact with the nozzle formation surface in advance, the ink is drawn out from the nozzle, and then the deposit dissolved in the drawn ink is removed from the nozzle formation surface. On the other hand, the rear surface of the wiper that is in sliding contact with the rear surface is scraped off.

  Further, in the printer of Patent Document 2, wiping is performed after the ink in the nozzle has oozed out to the nozzle forming surface by pressurization, so that the deposits are dissolved and removed in the ink.

JP 2001-063077 A JP 2008-221534 A

  By the way, as in Patent Document 1, when ink is drawn out from the nozzle during wiping, the ink is supplied by capillary force from the upstream side of the nozzle. However, since the back pressure of the liquid level in the nozzle is always negative, especially when wiping is performed at a high speed, the ink supply is not in time, and bubbles are mixed in the nozzle or the position of the liquid level is There has been a problem that it has moved backwards significantly, leading to missing dots.

  On the other hand, when the back pressure of the liquid level in the nozzle is set to a positive pressure as in the printer of Patent Document 2, the ink is quickly supplied even when the ink is drawn out from the nozzle. Is suppressed. However, when the wiper comes into contact with the liquid surface that has oozed out on the nozzle forming surface, the back pressure is positive, so that the ink continuously flows out through the wiper and the ink is wasted. there were.

  The present invention has been made in view of these problems, and an object thereof is to provide a fluid ejecting apparatus and a wiping method capable of suppressing the occurrence of dot dropout while suppressing the consumption of fluid associated with wiping. It is in.

  In order to achieve the above object, a fluid ejecting apparatus of the present invention includes a fluid ejecting head having a nozzle for ejecting fluid and a nozzle forming surface in which a nozzle opening of the nozzle is formed, and a relative movement with respect to the nozzle forming surface. A first sliding contact portion that draws the fluid from the nozzle by sliding contact while applying the fluid to the nozzle forming surface, and the nozzle forming surface after application of the fluid to the nozzle forming surface by the first sliding contact portion A second sliding contact portion that wipes the nozzle forming surface by sliding while moving relative to the nozzle, and pressurizing the fluid in the fluid ejecting head when the fluid is drawn, while forming the nozzle When the surface is wiped, the pressure adjustment is performed to reduce the pressure of the fluid in the fluid ejecting head so that the pressure of the fluid in the fluid ejecting head is lower than that during the pressurization. Includes a mechanism, a.

  According to this configuration, when the first sliding contact portion is in sliding contact with the nozzle forming surface, the pressure adjusting mechanism pressurizes the fluid in the fluid ejecting head. As the fluid is drawn, the fluid is quickly supplied into the nozzle. Thereby, occurrence of missing dots can be suppressed. On the other hand, when the second sliding contact portion is in sliding contact with the nozzle forming surface, the pressure adjustment mechanism performs pressure reduction so that the pressure of the fluid in the fluid ejecting head is lower than that during pressurization. Pulled into the nozzle, the contact between the second sliding contact portion and the liquid level is suppressed. Thereby, since the drawing-out of the fluid by the 2nd sliding contact part is suppressed, generation | occurrence | production of a dot missing can be suppressed, suppressing consumption of the fluid accompanying wiping.

  In the fluid ejecting apparatus according to the aspect of the invention, the pressure adjusting mechanism may be configured such that the pressure of the fluid in the fluid ejecting head that is the back pressure of the liquid level formed in the nozzle is equal to or higher than the pressure of the gas in contact with the liquid level. The pressurization is performed as follows.

  According to this configuration, the pressure adjusting mechanism pressurizes so that the back pressure of the liquid level formed in the nozzle is equal to or higher than the atmospheric pressure of the gas in contact with the liquid level. As the fluid is drawn, the fluid is quickly supplied into the nozzle.

In the fluid ejecting apparatus according to the aspect of the invention, the pressure adjusting mechanism may form a concave liquid surface in the nozzle by reducing the pressure of the fluid in the fluid ejecting head.
According to this configuration, since the concave liquid surface is formed in the nozzle due to the reduced pressure, the contact between the second sliding contact portion and the liquid surface is suppressed when the second sliding contact portion wipes the nozzle forming surface. Is done.

  The fluid ejecting apparatus according to the aspect of the invention further includes a wiper that can reciprocate along the nozzle forming surface, and the first sliding contact portion is provided on one surface side of the wiper, and the nozzle moves with the forward movement of the wiper. The second sliding contact portion is provided on the other surface side of the wiper while being in sliding contact with the forming surface, and is in sliding contact with the nozzle forming surface as the wiper moves backward, and the pressure adjusting mechanism moves forward of the wiper. The pressure is sometimes applied, while the pressure is reduced when the wiper moves backward.

  According to this configuration, the first slidable contact portion is provided on the one surface side of the wiper, while the second slidable contact portion is provided on the other surface side of the wiper. Therefore, it is not necessary to provide a plurality of wipers. Further, since the first sliding contact portion comes into sliding contact with the nozzle forming surface when the wiper moves in the forward direction and the second sliding contact portion comes into sliding contact with the nozzle formation surface when the wiper moves in the backward direction, wiping is performed as the wiper reciprocates. Can do. Since the pressure adjustment mechanism performs pressurization when the wiper moves in the forward path, and only needs to perform pressure reduction when the wiper moves in the backward path, control of pressure adjustment can be simplified.

In the fluid ejecting apparatus according to the aspect of the invention, the first sliding contact portion has higher affinity for the fluid than the second sliding contact portion.
According to this configuration, since the first sliding contact portion has a higher affinity for the fluid than the second sliding contact portion, the fluid can be efficiently drawn out when contacting the liquid level in the nozzle. On the other hand, since the second sliding contact portion has low affinity for the fluid, it is difficult for the fluid to be drawn even if it contacts the liquid level in the nozzle. Therefore, when wiping by the second sliding contact portion, consumption of fluid is suppressed and occurrence of missing dots is suppressed.

  In order to achieve the above object, a wiping method of the present invention is a wiping method for wiping a nozzle forming surface in which a nozzle opening of the nozzle is formed in a fluid ejecting head provided with a nozzle for ejecting a fluid. In a state where the fluid in the fluid ejecting head is pressurized, the first sliding contact portion slides while moving relative to the nozzle forming surface, draws the fluid from the nozzle, and applies the fluid to the nozzle forming surface. After the first sliding contact step and after the first sliding contact step, the fluid in the fluid ejecting head is depressurized so that the pressure of the fluid in the fluid ejecting head is lower than that during the pressurization. A second sliding contact step in which the second sliding contact portion is in sliding contact with the nozzle forming surface while moving relative to the nozzle forming surface and wipes the nozzle forming surface.

  According to this configuration, in the first sliding contact step, the first sliding contact portion draws the fluid from the nozzle while the fluid in the fluid ejecting head is pressurized, so that the fluid can be quickly replaced with the drawn fluid. The fluid is supplied into the nozzle, and the occurrence of missing dots can be suppressed. Further, in the second sliding contact process, the second sliding contact portion wipes the nozzle forming surface in a state where the pressure of the fluid in the fluid ejecting head is reduced so as to be lower than that during pressurization, so that the liquid level is kept in the nozzle. The contact between the second sliding contact portion and the liquid level can be suppressed. Thereby, generation | occurrence | production of a dot missing can be suppressed, suppressing consumption of the fluid accompanying wiping.

1 is a schematic diagram illustrating a schematic configuration of an ink jet printer according to an embodiment. Sectional drawing which shows schematic structure of a wiping apparatus. The block diagram which shows the electric constitution of a control apparatus. 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. It is a schematic diagram for demonstrating wiping, (a) is a steady state, (b) shows a 1st sliding contact process, (c) shows a 2nd sliding contact process. The flowchart which shows a wiping process.

  Hereinafter, an embodiment in which the present invention is embodied in an ink jet printer (hereinafter simply referred to as “printer”) which is a kind of fluid ejecting apparatus will be described with reference to FIGS. 1 to 6. 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 mechanism 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 mechanism 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 (front-rear direction) of the paper P, and the maintenance unit 15 is disposed between the conveyor belts 17 arranged in the front-rear direction. Is arranged.

  The line head 13 includes a support portion 22 and a fluid ejecting head 24 supported by the support portion 22. The fluid ejecting head 24 is provided with a plurality of nozzles 25 for ejecting ink. In addition, nozzle openings 25 a of a plurality of nozzles 25 are formed on a nozzle forming surface 24 a formed from the lower surface (bottom surface) of the fluid ejecting head 24.

  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. It is done. Then, the printing process is executed by superposing four color ink droplets on the conveyed paper P from the four line heads 13 supported by the support unit 22.

  The ink supply unit 14 includes an ink cartridge 26 that contains ink, an elastically deformable ink supply tube 27 that forms a fluid supply path that supplies ink from the ink cartridge 26 toward the fluid ejection head 24, and an ink supply unit. And a pressurizing pump 28 for supplying pressure. The ink cartridge 26 is connected to the ink supply tube 27 by being detachably mounted on a cartridge holder (not shown). Further, a differential pressure valve 29 and a pressure adjusting mechanism 30 are provided in the middle of the ink supply tube 27.

  As shown in an enlarged cross-sectional view of a portion surrounded by a two-dot chain line in FIG. 1, in the fluid ejecting head 24, the upstream side communicates with the ink supply tube 27 through an ink flow path (not shown), while the downstream side communicates with the nozzle 25. A cavity 31 is formed. The upper wall surface of the cavity 31 is constituted by a diaphragm 32, and a piezoelectric element 33 is disposed on the upper surface side of the diaphragm 32 at a position above the cavity 31. The nozzle 25 is formed by penetrating a nozzle plate 34 that constitutes the lower surface of the fluid ejecting head 24.

  The diaphragm 32 is attached so as to vibrate in the vertical direction, and the piezoelectric element 33 expands and contracts in response to the drive signal to vibrate the diaphragm 32 in the vertical direction. Further, when the diaphragm 32 vibrates in the vertical direction, the volume of the cavity 31 is expanded and contracted. When the volume of the cavity 31 is reduced, the ink supplied into the cavity 31 via the ink supply tube 27 is ejected from the nozzle 25 as ink droplets.

  The nozzle 25 is formed so as to have a high affinity (wetting property) with ink. Therefore, a concave liquid surface Sf (meniscus) is formed in the nozzle 25. Here, the meniscus is a curved shape caused by the magnitude relationship between the adhesion force acting between the molecules and the cohesive force between the fluid molecules when the fluid (ink) is in contact with the solid surface (nozzle 25 or nozzle forming surface 24a). The fluid surface.

Next, the maintenance unit 15 will be described.
The maintenance unit 15 includes a pressure adjusting mechanism 30, a capping device 35 for capping the nozzle forming surface 24a of the fluid ejecting head 24, a wiping device 36 (see FIG. 2) for wiping the nozzle forming surface 24a, and a control. The apparatus 100 (refer FIG. 3) is provided. The pressure adjusting mechanism 30, the capping device 35, and the wiping device 36 are provided for each fluid ejecting head 24.

  The pressure adjusting mechanism 30 includes a rotating shaft 30a and a cam member 30b that rotates together with the rotating shaft 30a. The pressure adjustment mechanism 30 pressurizes the ink in the ink supply tube 27 and the fluid ejection head 24 by crushing the ink supply tube 27 as the cam member 30b rotates in the positive direction of the rotation shaft 30a. It is like that. Further, when the cam member 30b of the pressure adjusting mechanism 30 rotates in the reverse direction and returns to the original position, the pressurization is released.

  The capping device 35 is used for capping to prevent the nozzle 25 from drying, and also performs suction cleaning for discharging air bubbles and thickened ink by sucking ink in the ink cartridge 26 from the nozzle 25. Used when. Further, the capping device 35 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.

  As shown in FIG. 1, the capping device 35 includes a bottomed rectangular box-shaped cap 37, a lifting mechanism 38 that lifts and lowers the cap 37, and a suction pump 39. When the suction pump 39 is driven in a state where the cap 37 moved upward by the elevating mechanism 38 is in contact with the nozzle forming surface 24a, suction cleaning in which ink is discharged from the nozzle 25 is executed.

The wiping device 36 is used when performing wiping for wiping the nozzle forming surface 24a to remove deposits such as paper dust and ink.
As shown in FIG. 2, the wiping device 36 includes a holder 40, a lead screw 41 installed on the holder 40 so as to extend in the front-rear direction, a motor 42 for rotating the lead screw 41, and a support member 43. And a plate-like wiper 44 made of an elastic body such as rubber. The wiper 44 is supported in a manner standing on the support member 43, and the support member 43 is supported by the lead screw 41. A storage recess 45 is formed on the upper surface side of the support member 43.

  The wiping device 36 can be moved up to a position where the wiper 44 comes into contact with the nozzle forming surface 24 a by the lifting mechanism 38. When the motor 42 is driven in the forward direction, the wiper 44 moves forward along with the support member 43 as the lead screw 41 rotates in the forward direction. On the other hand, when the motor 42 is driven in the reverse direction, the wiper 44 moves backward along with the support member 43 as the lead screw 41 rotates in the reverse direction. Therefore, as the motor 42 is driven, the wiper 44 can reciprocate along the nozzle forming surface 24a.

  As shown in the partially enlarged view of FIG. 2, a first sliding contact portion 44 a having high surface roughness and high affinity for ink is formed on one surface side (front surface side) of the wiper 44. Further, on the other surface side (back side) of the wiper, a second sliding contact portion 44b having a low surface roughness and having a lower affinity for ink than the first sliding contact portion 44a is formed. The first sliding contact portion 44a slides in contact with the nozzle forming surface 24a while moving relative to the nozzle forming surface 24a as the wiper 44 moves forward, thereby drawing out ink from the nozzle 25 and the nozzle forming surface 24a. It is designed to be applied to. On the other hand, the second sliding contact portion 44b is moved relative to the nozzle forming surface 24a as the wiper 44 moves backward after the ink is applied to the nozzle forming surface 24a by the first sliding contact portion 44a. The nozzle forming surface 24a is wiped off by sliding on the nozzle.

  In this manner, wiping for cleaning the nozzle forming surface 24a by wiping is performed as the wiper 44 reciprocates. At this time, the ink or paper powder wiped from the nozzle forming surface 24 a flows down through the wiper 44 and is stored in the storage recess 45.

Next, the electrical configuration of the control device 100 and the maintenance unit 15 will be described.
As illustrated in FIG. 3, the control device 100 includes a CPU 150 that functions as a selection unit, a ROM 151, a RAM 152, and a nonvolatile memory 153. The ROM 151 stores a control program executed by the CPU 150 and the like. Further, the RAM 152 temporarily stores calculation results of the CPU 150 and various data to be processed by executing the control program. The rewritable nonvolatile memory 153 stores an operation history of the printer 11 and the like.

  The control device 100 further includes motor drive circuits 154 to 157, which are connected to the CPU 150, the ROM 151, the RAM 152, and the nonvolatile memory 153 via the bus 160. Then, the CPU 150 performs drive control of the maintenance unit 15. The control device 100 may also be used as a control device that controls the overall operation of the printer 11.

  Specifically, the CPU 150 drives and controls the motor 46 for rotating the rotation shaft 30 a of the pressure adjustment mechanism 30 via the motor drive circuit 154. Further, the CPU 150 drives and controls the pump motor 47 for driving the suction pump 39 of the capping device 35 via the motor drive circuit 155, and moves the cap 37 and the wiper 44 up and down via the motor drive circuit 156. The motor 48 of the lifting mechanism 38 is driven and controlled. Further, the CPU 150 drives and controls the motor 42 for moving the wiper 44 of the wiping device 36 in the front-rear direction via the motor drive circuit 157.

  Next, the differential pressure valve 29 will be described. The differential pressure valve 29 is a diaphragm-type self-sealing valve that opens and closes using a differential pressure between atmospheric pressure and ink pressure, and is disposed between the ink cartridge 26 and the pressure adjustment mechanism 30.

  As shown in FIG. 4A, the differential pressure valve 29 has a flow path forming member 50 having a regularity. One end of the flow path forming member 50 (left end in FIG. 4) is provided with a connecting portion 51 connected to the upstream ink supply tube 27 communicating with the ink cartridge 26. On the other hand, a connecting portion 52 connected to the downstream ink supply tube 27 communicating with the fluid ejecting head 24 is provided at the right end of the flow path forming member 50. Further, a concave portion 50a having a circular shape in a plan view is formed on one surface side (the upper surface side in FIG. 4) of the flow path forming member 50, and a conical shape is provided at a position eccentric to the left from the center on the inner bottom surface of the concave portion 50a. One trapezoidal convex portion 50b is formed. An inflow passage 51a is formed in the connection portion 51 to allow the upstream ink supply tube 27 and the recess 50a to communicate with each other so that an opening into the recess 50a is formed on the upper end surface of the protrusion 50b. ing. On the other hand, in the connection portion 52, an outflow path 52a that connects the downstream ink supply tube 27 and the inside of the recess 50a is formed.

  On the upper surface side of the flow path forming member 50, a flexible film member 53 is fixed in a bent state so as to seal the opening of the recess 50a. Further, a disc-shaped pressing plate 54 having an area smaller than the opening area of the recess 50a is fixed to the substantially central portion on the inner surface facing the recess 50a of the film member 53. And the pressure chamber 55 is enclosed and formed by the film member 53 and the recessed part 50a.

  In the pressure chamber 55, a base part 56, an arm member 57 supported by the base part 56 in a tiltable manner, and one end side (left end side) of the arm member 57 are attached to the convex part 50b side. A biasing spring 58 that biases is accommodated. The arm member 57 normally receives the urging force of the urging spring 58, and seals the opening of the inflow passage 51a provided at the upper end surface of the convex portion 50b at one end side and presses the other end side (right end side). The plate 54 is pushed upward.

  As a result, the film member 53 is deflected and displaced in a direction in which the internal volume of the pressure chamber 55 is enlarged, and the pressure in the pressure chamber 55 and the fluid ejecting head 24 located in the downstream area is negative. In addition, ink is supplied to the inflow passage 51 a in a pressurized state by the pressurizing pump 28, and is always supplied into the pressure chamber 55 by one end side of the arm member 57 that receives the biasing force of the biasing spring 58. Inflow is suppressed.

  When ink is consumed by ejection or outflow from the nozzle 25, the negative pressure in the pressure chamber 55 increases, and the film member 53 resists the urging force of the urging spring 58 as shown in FIG. Thus, the pressure chamber 55 is deflected and displaced in a direction to reduce the internal volume of the pressure chamber 55. Then, the other end side of the arm member 57 is pressed and tilted by the film member 53 via the pressing plate 54, and the one end side opens the opening of the inflow passage 51a, so that the pressure chamber 55 is pressurized through the inflow passage 51a. Ink flows in.

  When the negative pressure in the pressure chamber 55 decreases with the inflow of ink, the arm member 57 and the film member 53 are returned to their original positions again by the biasing force of the biasing spring 58. Therefore, ink corresponding to the amount of consumption is supplied to the fluid ejecting head 24.

  As described above, when the differential pressure valve 29 is in a closed state where the steady state is reached, the pressure in the pressure chamber 55 and the fluid ejecting head 24 located on the downstream side is negative. In the printer 11, the pressure of the ink in the fluid ejecting head 24 (hereinafter referred to as “back pressure”) is set to about −1 kPa by the differential pressure valve 29 in order to prevent the ink from dropping due to gravity and to stabilize the ejecting operation. Holding at negative pressure.

  That is, in this embodiment, the ink in the fluid ejecting head 24 is decompressed in preparation for the ink ejecting operation, and the concave liquid level Sf is formed in the nozzle 25 as shown in FIG. Is in a steady state. FIG. 5A shows the liquid surface position when the inside of the fluid ejecting head 24 is depressurized to about −1 kPa by the differential pressure valve 29 (hereinafter referred to as “at the time of depressurization”).

  In a steady state, the liquid level Sf is formed in the nozzle 25 so that the boundary of the liquid level Sf is in contact with the nozzle opening 25a and the vicinity of the center of the liquid level Sf is drawn into the nozzle. Then, the boundary of the liquid surface Sf is clipped to the nozzle opening 25a, so that even if the back pressure changes within a predetermined range, the position of the boundary of the liquid surface Sf does not change and only the curvature changes. It has become. “Clipped” refers to a state in which the liquid surface Sf is caught by a portion where the shape or surface state changes, and the liquid surface position is less likely to move than a flat portion. In the steady state, the curvature of the liquid level Sf formed in the nozzle 25 is larger than that when the back pressure is equal to the pressure of the gas in contact with the liquid level Sf (atmospheric pressure in this embodiment). The back pressure is displayed as a differential pressure (gauge pressure) with respect to the pressure of the gas in contact with the liquid level Sf.

Next, wiping in the present embodiment will be described.
At the time of wiping, the wiper 44 is in sliding contact with the nozzle forming surface 24a with the tip elastically deformed in order to scrape off the adhered matter. Therefore, when the wiper 44 passes through the nozzle opening 25a, it may enter the nozzle 25 and come into contact with the ink surface Sf. At this time, if the adhesion force (wetting property) acting between the wiper 44 and the ink is large, the ink in the nozzle 25 is drawn out by the wiper 44. In addition, when the wiper 44 is made of a material having a high affinity with the ink or a material having a rough surface, or when the thickened ink or paper powder scraped on the wiper 44 is adhered, Adhesive force acting between the two increases.

  When ink is drawn from the nozzle 25 during wiping, the ink is supplied from the cavity 31 on the upstream side of the nozzle 25 by capillary force. However, since the back pressure of the ink is always kept at a negative pressure, particularly when wiping is performed at a high speed, the supply of ink is not in time, and bubbles are mixed in the nozzle 25 or the liquid level position is large inside. Or retreat. Such mixing of bubbles and the receding position of the liquid level cause dot dropout when printing is performed.

  Dot omission due to wiping is caused by the fact that ink supply due to capillary force is not in time for the outflow of ink, so it can be said that it is more likely to occur as the back pressure is lower, and it is less likely to occur as the back pressure is higher. However, if the wiper 44 comes into contact with the liquid level Sf with the back pressure being positive, the ink may continue to bleed and the ink may be wasted.

  Therefore, in the printer 11, when the first sliding contact portion 44 a of the wiper 44 pulls out the ink from the nozzle 25, the pressure adjusting mechanism 30 pressurizes the ink in the fluid ejecting head 24. On the other hand, when the first sliding contact portion 44a of the wiper 44 wipes the nozzle forming surface 24a, the pressure adjustment mechanism 30 releases the pressurization so that the pressure of the ink in the fluid ejecting head 24 is lower than that during pressurization. By doing so, the ink in the fluid ejecting head 24 is decompressed.

  In the following description, the steady state of the fluid ejecting head 24 described above is referred to as “during pressure reduction”, while the pressure adjustment mechanism 30 pressurizes the decompressed ink in the fluid ejecting head 24 as “pressurization”. "Time". When the pressure adjustment mechanism 30 releases the pressurization, the ink in the fluid ejecting head 24 is depressurized more than the pressurization, and the concave liquid level Sf is formed in the nozzle 25 as in the steady state. .

  Here, at the time of pressurization, it is preferable that the boundary of the liquid surface Sf is clipped to the step of the nozzle opening 25a. This is because when the liquid level Sf is in a state of being wet and spread on the nozzle forming surface 24a, the contact time between the wiper 44 and the liquid level Sf becomes long, and ink is continuously drawn out.

  In addition, when the back pressure is equal to the atmospheric pressure, the liquid surface Sf has a concave shape due to the capillary force and the wettability of the nozzle 25. Therefore, when the back pressure becomes a positive pressure slightly higher than the atmospheric pressure, the liquid surface Sf. Becomes a planar shape with zero curvature. If the back pressure is about −1 kPa, the probability of missing dots is 80% or more, whereas if the back pressure is 0.3 to 1 kPa, the probability of missing dots is reduced to about 20%. The experimental results are obtained. Further, if the back pressure exceeds 3 kPa, the ink may drop from the nozzle opening 25a. Therefore, the back pressure at the time of pressurization is preferably set to atmospheric pressure or more, and particularly preferably about 0 to 2 kPa.

Next, wiping execution processing by the CPU 150 will be described with reference to FIG.
As shown in FIG. 6, when the control device 100 receives the wiping execution command, the CPU 150 drives and controls the motor 48 of the lifting mechanism 38 in the forward direction so as to apply the wiper 44 to the nozzle forming surface 24a as the ascending process of step S11. Raise to contact position. Next, as a pressurizing step in step S12, the CPU 150 drives and controls the motor 46 of the pressure adjusting mechanism 30 in the forward direction to rotate the cam member 30b in the forward direction. As a result, the ink in the fluid ejecting head 24 is pressurized and the back pressure becomes positive.

  Next, as a first sliding contact process in step S13, the CPU 150 drives and controls the motor 42 of the wiping device 36 in the forward direction to move the wiper 44 forward as shown in FIG. 5B. As a result, in a state where the ink in the fluid ejecting head 24 is pressurized by the pressure adjusting mechanism 30, the first sliding contact portion 44 a comes into sliding contact with the nozzle forming surface 24 a while moving relative thereto, and draws ink from the nozzle 25. To the nozzle forming surface 24a. And when the 1st sliding contact part 44a contacts the liquid level Sf, the back pressure is a positive pressure. Therefore, even when the wiper 44 moves forward at a high speed, ink is quickly supplied into the nozzle 25 as the wiper 44 draws out the ink.

  Next, as a depressurization step of step S14, the motor 46 of the pressure adjusting mechanism 30 is driven and controlled in the reverse direction to rotate the cam member 30b in the direction opposite to the pressurization step. In the case where the rotating shaft 30a is rotated 180 degrees in the pressurizing process, the rotating shaft 30a may be rotated 180 degrees in the same direction as the pressurizing process in the pressurizing release process. Thereby, the pressurization by the pressure adjusting mechanism 30 is released, and the back pressure returns to a negative pressure of about −1 kPa.

  Next, as a second sliding contact process in step S15, the CPU 150 controls the motor 42 of the wiping device 36 in the reverse direction to move the wiper 44 in the backward direction as shown in FIG. 5C. Thereby, in a state where the back pressure is reduced so as to be lower than that during pressurization, the second sliding contact portion 44b is slidably contacted with the nozzle forming surface 24a while being relatively moved, and wipes the nozzle forming surface 24a. At this time, since the back pressure is a negative pressure, the outflow of ink is suppressed even when the second sliding contact portion 44b contacts the liquid surface Sf.

Finally, as the lowering step of step S16, the CPU 150 drives and controls the motor 48 of the elevating mechanism 38 in the reverse direction to lower the wiper 44 to the original position, and the process ends.
According to the embodiment described above, the following effects can be obtained.

  (1) When the first sliding contact portion 44a is in sliding contact with the nozzle forming surface 24a, the pressure adjusting mechanism 30 pressurizes the ink in the fluid ejecting head 24. As ink is drawn out from the inside of the nozzle 25, the ink is quickly supplied into the nozzle 25. Thereby, occurrence of missing dots can be suppressed. On the other hand, when the second sliding contact portion 44b is in sliding contact with the nozzle forming surface 24a, the pressure adjustment mechanism 30 releases the pressure so that the back pressure is lower than that during the pressurization. The liquid surface Sf is drawn into the nozzle 25, and the contact between the second sliding contact portion 44b and the liquid surface Sf is suppressed. Thereby, since the drawing of the ink by the second sliding contact portion 44b is suppressed, it is possible to suppress the occurrence of dot omission while suppressing the consumption of the ink accompanying the wiping.

  (2) The pressure adjusting mechanism 30 pressurizes the liquid surface Sf formed in the nozzle 25 so that the back pressure becomes equal to or higher than the atmospheric pressure, so that the ink is drawn from the nozzle 25 by the first sliding contact portion 44a. As a result, ink is quickly supplied into the nozzle 25.

  (3) Since the concave liquid surface Sf is formed in the nozzle 25 by decompression, when the second sliding contact portion 44b wipes the nozzle forming surface 24a, the second sliding contact portion 44b and the liquid surface Sf Contact is suppressed.

  (4) Since the first slidable contact portion 44 a is provided on one surface side of the wiper 44, the second slidable contact portion 44 b is provided on the other surface side of the wiper 44, so that it is not necessary to provide a plurality of wipers 44. Further, when the wiper 44 moves forward, the first sliding contact portion 44a comes into sliding contact with the nozzle forming surface 24a, and when the wiper 44 moves backward, the second sliding contact portion 44b comes into sliding contact with the nozzle forming surface 24a. Accordingly, wiping can be performed. Since the pressure adjusting mechanism 30 performs pressurization when the wiper 44 moves in the forward path, while pressure reduction (release of pressurization) may be performed when the wiper 44 moves in the backward path, control of pressure adjustment can be simplified.

  (5) Since the first sliding contact portion 44a has a higher affinity for ink than the second sliding contact portion 44b, the ink can be efficiently drawn out when it contacts the liquid surface Sf in the nozzle 25. On the other hand, since the second sliding contact portion 44b has a low affinity for the ink, the ink is hardly pulled out even if it contacts the liquid surface Sf in the nozzle 25. Therefore, when wiping by the second sliding contact portion 44b, ink consumption is suppressed and occurrence of missing dots is suppressed.

  Further, since the second sliding contact portion 44b has a low affinity for ink, it is possible to quickly cause the deposits to flow down toward the storage recess 45. As a result, it is possible to prevent the affinity for ink from increasing due to the adhering matter adhering to the second sliding contact portion 44b.

  (6) In the first sliding contact step, since the first sliding contact portion 44a pulls out the ink from the nozzle 25 in a state where the ink in the fluid ejecting head 24 is pressurized, it can be quickly replaced with the drawn ink. Ink is supplied into the nozzle 25, and the occurrence of missing dots can be suppressed. Further, in the second sliding contact step, the second sliding contact portion 44b wipes the nozzle forming surface 24a in a state where the pressure of the ink in the fluid ejecting head 24 is reduced so as to be lower than that during pressurization. Sf can be drawn into the nozzle 25 to suppress contact between the second sliding contact portion 44b and the liquid level Sf. Thereby, it is possible to suppress the occurrence of missing dots while suppressing the consumption of ink accompanying wiping.

The above embodiment may be changed to another embodiment as described below.
In the first sliding contact step, pressure is applied so that the pressure adjustment mechanism 30 forms a convex liquid surface Sf, while in the second sliding contact step, the pressure adjustment mechanism 30 forms a flat liquid surface Sf. The pressurizing force may be adjusted as described above. That is, the back pressure in the second sliding contact process may be equal to or higher than atmospheric pressure. In this case, the adhering matter can be prevented from being mixed into the nozzle 25.

  In the first sliding contact step, the position of the boundary of the liquid level Sf may be held before and after the pressurization, and the pressurization may be performed in a range in which the vicinity of the center of the liquid level Sf does not bulge from the nozzle opening. That is, the pressing force may be adjusted within a range in which the curvature of the concave liquid surface Sf is smaller than that in the steady state.

The pressure applied by the pressure adjusting mechanism 30 may be changed according to the moving speed of the wiper 44, the shape of the wiper 44, etc. (wetting property).
An open / close valve that can be opened / closed at an arbitrary timing may be provided between the differential pressure valve 29 of the ink supply tube 27 and the pressure adjustment mechanism 30. In this case, at the time of suction cleaning or pressure cleaning, the on-off valve is closed and then suction or pressurization is performed, and the on-off valve is opened with the pressure in the ink flow path increased. As a result, the flow rate of the ink can be increased and the bubble discharge performance can be improved. Further, by closing the on-off valve when pressurizing by the pressure adjusting mechanism 30, it is possible to suppress the applied pressure from reaching the upstream side and concentrate the applied pressure on the downstream side.

  The differential pressure valve 29 may not be provided. Also in this case, a concave liquid surface may be formed in the nozzle 25 depending on the type of fluid and the wettability of the nozzle 25. Further, by disposing the ink cartridge 26 (cartridge holder not shown) at a position lower than the fluid ejecting head 24, the inside of the fluid ejecting head 24 can be set to a negative pressure due to a water head difference.

  -You may form a 1st sliding contact part and a 2nd sliding contact part in the separate member which can move separately. In this case, it is possible to realize shapes optimized for ink drawing and wiping, such as making the first sliding contact portion into a brush shape and making the second sliding contact portion into a plate shape. Alternatively, the amount of ink drawn out by the second sliding contact portion may be suppressed by making the first sliding contact portion longer than the second sliding contact portion.

  The first sliding contact portion 44a may be formed by increasing the surface roughness on one surface side of the wiper 44, or the first sliding contact portion 44a and the second sliding contact portion 44b made of different materials The wiper 44 may be configured by stacking layers.

-You may make it change the moving speed of the wiper 44 by a 1st sliding contact process and a 2nd sliding contact process.
The affinity for ink may be equal on one side of the wiper 44 and the other side.

The surface roughness may be made equal between the first sliding contact portion 44a and the second sliding contact portion 44b, while the shape and elastic force may be changed.
-You may employ | adopt the pressure adjustment mechanism provided with the piezoelectric element and the pump. In this case, the fluid supply path can be composed of a rigid pipe line that is not easily elastically deformed. Thereby, the pressure fluctuation accompanying pressurization etc. can be propagated in the fluid ejecting head 24 without being absorbed by the elastic deformation of the pipe line.

  When ink is supplied from one ink cartridge 26 to a plurality of fluid ejecting heads 24, the pressure adjustment mechanism 30 is provided in a single fluid supply path (ink supply tube 27) connected to the ink cartridge 26. Alternatively, the pressure adjusting mechanism 30 may be provided for each fluid ejecting head 24.

The ink cartridge 26 may be an ink tank that is not attached or detached.
The number of fluid ejecting heads 24 and nozzles 25 can be set arbitrarily.
The printer 11 may be realized as a full-line type line head printer having a long fluid ejection head, a lateral printer, or a serial 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 ... Printer as fluid ejecting apparatus, 24 ... Fluid ejecting head, 24a ... Nozzle formation surface, 25 ... Nozzle, 25a ... Nozzle opening, 44 ... Wiper, 44a ... First sliding contact portion, 44b ... Second sliding contact portion, 30: Pressure adjusting mechanism, Sf: Liquid level.

Claims (6)

A fluid ejecting head having a nozzle that ejects fluid and a nozzle forming surface in which a nozzle opening of the nozzle is formed;
A first sliding contact portion that draws the fluid out of the nozzle and applies it to the nozzle forming surface by sliding while moving relative to the nozzle forming surface;
A second sliding contact portion for wiping the nozzle forming surface by sliding while moving relative to the nozzle forming surface after application of the fluid to the nozzle forming surface by the first sliding contact portion;
When the fluid is drawn out, the fluid in the fluid ejecting head is pressurized, while the nozzle forming surface is wiped so that the pressure of the fluid in the fluid ejecting head is lower than that during the pressurizing. A pressure adjusting mechanism for depressurizing the fluid in the fluid ejecting head;
A fluid ejecting apparatus comprising: The pressure adjusting mechanism performs the pressurization so that the pressure of the fluid in the fluid ejecting head, which is the back pressure of the liquid level formed in the nozzle, is equal to or higher than the pressure of the gas in contact with the liquid level. The fluid ejecting apparatus according to claim 1. The pressure adjusting mechanism forms a concave liquid level in the nozzle by reducing the pressure of the fluid in the fluid ejecting head. Fluid ejection device. Further comprising a wiper capable of reciprocating along the nozzle forming surface;
The first sliding contact portion is provided on one surface side of the wiper and slidably contacts the nozzle forming surface as the wiper moves forward, while the second sliding contact portion is provided on the other surface side of the wiper. As the wiper moves backward, it comes into sliding contact with the nozzle forming surface,
4. The fluid according to claim 1, wherein the pressure adjusting mechanism performs the pressurization when the wiper moves in the forward path, and performs the pressure reduction when the wiper moves in the backward path. 5. Injection device. 5. The fluid ejecting apparatus according to claim 1, wherein the first sliding contact portion has higher affinity for the fluid than the second sliding contact portion. A wiping method for wiping a nozzle forming surface in which a nozzle opening of the nozzle is formed in a fluid ejecting head provided with a nozzle for ejecting fluid,
In a state where the fluid in the fluid ejecting head is pressurized, the first sliding contact portion is in sliding contact with the nozzle forming surface while moving relative to the nozzle forming surface, and the fluid is drawn out from the nozzle and applied to the nozzle forming surface. A first sliding contact process,
After the first sliding contact step, the second sliding is performed in a state where the pressure in the fluid in the fluid ejecting head is reduced so that the pressure of the fluid in the fluid ejecting head is lower than that in the pressurization. And a second sliding contact step in which the contact portion slides while moving relative to the nozzle forming surface and wipes the nozzle forming surface.

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