JP5428917B2 - Fluid ejecting apparatus and wiping method - Google Patents

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. In addition, when the back pressure is negative, clogging occurs due to the adhering material scraped off by the wiper being pushed into the nozzle, which may cause 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 supplied quickly even when the ink is drawn out from the nozzle. In order to suppress entry, occurrence of missing dots 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 wipes a fluid ejecting head provided with a nozzle for ejecting fluid and a nozzle forming surface in which the nozzle opening of the nozzle is formed in the fluid ejecting head. The wiper and the first wiping and the back pressure performed by making the pressure of the fluid in the fluid ejecting head, which is the back pressure of the liquid level formed in the nozzle, larger than the pressure of the gas in contact with the liquid level Selection means for selecting one of the second wiping operations performed at a pressure lower than the atmospheric pressure as a wiping method, and the selection means forcibly causes the fluid in the nozzle to be forced from the nozzle opening before the wiping operation is performed. The first wiping is selected when the cleaning is to be discharged automatically .

  According to this configuration, since the back pressure of the liquid level is larger than the atmospheric pressure during the first wiping, the fluid is quickly supplied even if the wiper comes into contact with the liquid level and the fluid is pulled out from the inside of the nozzle. , Mixing of foreign substances and the like is suppressed. Thereby, it is possible to suppress the occurrence of missing dots due to wiping. On the other hand, since the back pressure of the liquid level is equal to or lower than the atmospheric pressure during the second wiping, the fluid does not continuously flow out from the nozzle even if the wiper contacts the liquid level. Therefore, by selectively performing one of the first wiping and the second wiping as necessary, it is possible to suppress the occurrence of dot omission while suppressing the consumption of fluid accompanying the wiping.

In addition , since the selection unit selects the wiping method based on the operation of the fluid ejection device before the wiping is performed, either the first wiping or the second wiping can be selectively executed according to the situation.

Then , by selectively performing the first wiping after the cleaning that is highly likely to have foreign matters attached to the nozzle formation surface, the foreign matters can be prevented from being mixed into the nozzles.

  The fluid ejecting apparatus according to the aspect of the invention may further include a transport mechanism that transports the medium that receives the fluid, and the selection unit is configured such that the transport amount of the medium before the wiping is equal to or greater than a predetermined threshold. Selects the first wiping, but selects the second wiping when the transport amount of the medium before the wiping is less than the threshold.

  According to this configuration, when the transport amount of the medium before the wiping is equal to or more than a predetermined threshold value, there is a high possibility that foreign matter is attached to the nozzle formation surface. Therefore, the first wiping is selectively performed. By executing this, it is possible to suppress the entry of foreign matter into the nozzle. On the other hand, when the transport amount of the medium before the wiping is less than the threshold value, there is a low possibility that foreign matter has adhered to the nozzle formation surface. Therefore, by selectively executing the second wiping, the wiping is accompanied. The consumption of fluid can be suppressed.

In the fluid ejecting apparatus of the present invention, the selection means, while when the wiping performed before operation was injection of the fluid is selected the first wiping, injection said wiping performed before operation of said fluid If not, the second wiping is selected.

  According to this configuration, after the fluid has been ejected, the first wiping is selectively performed because there is a high possibility that foreign matter has adhered to the nozzle forming surface due to transport of a medium that receives the fluid or the like. Thereby, mixing of the foreign material in a nozzle can be suppressed. On the other hand, since it is unlikely that foreign matter has adhered to the nozzle forming surface before the fluid is ejected, the consumption of fluid accompanying wiping can be suppressed by selectively executing the second wiping. .

In order to achieve the above object, a fluid ejecting apparatus of the present invention wipes a fluid ejecting head provided with a nozzle for ejecting fluid and a nozzle forming surface in which the nozzle opening of the nozzle is formed in the fluid ejecting head. The wiper and the first wiping performed by setting the pressure of the fluid in the fluid ejection head, which is the back pressure of the liquid level formed in the nozzle, to be equal to or higher than the pressure of the gas in contact with the liquid level, and the back pressure is the pressure Selection means for selecting one of the second wiping operations performed at a smaller size as a wiping method, and the selection means forcibly moves the fluid in the nozzle from the nozzle opening before the wiping operation is performed. If the cleaning is to be discharged, the first wiping is selected .

  According to this configuration, since the back pressure of the liquid level is equal to or higher than the atmospheric pressure during the first wiping, the fluid is promptly supplied even when the wiper comes into contact with the liquid level and the fluid is pulled out from the nozzle. Mixing of foreign substances and the like is suppressed. Thereby, it is possible to suppress the occurrence of missing dots due to wiping. On the other hand, since the back pressure of the liquid level is smaller than the atmospheric pressure during the second wiping, the fluid does not continuously flow out of the nozzle even if the wiper contacts the liquid level. Therefore, by selectively performing one of the first wiping and the second wiping as necessary, it is possible to suppress the occurrence of dot omission while suppressing the consumption of fluid accompanying the wiping.

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. The first wiping performed by making the pressure of the fluid in the fluid ejection head, which is the back pressure of the liquid level formed in the nozzle, larger than the pressure of the gas in contact with the liquid level, and the back pressure to be equal to or lower than the pressure. A selection step of selecting any one of the second wiping methods performed as a wiping method, and the operation before the wiping is cleaning for forcibly discharging the fluid in the nozzle from the nozzle opening. Selects the first wiping in the selection step .

  According to this configuration, since either the first wiping or the second wiping is selected as the wiping method in the selection stage, it is possible to execute appropriate wiping according to the situation. That is, since the back pressure of the liquid level is larger than the atmospheric pressure during the first wiping, the fluid is quickly supplied even if the wiper comes into contact with the liquid level and the fluid is pulled out from the nozzle, Mixing is suppressed. Thereby, it is possible to suppress the occurrence of missing dots due to wiping. On the other hand, since the back pressure of the liquid level is equal to or lower than the atmospheric pressure during the second wiping, the fluid does not continuously flow out from the nozzle even if the wiper contacts the liquid level. Therefore, by selectively performing one of the first wiping and the second wiping as necessary, it is possible to suppress the occurrence of dot omission while suppressing the consumption of fluid accompanying the 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) is the time of the 1st wiping, (c) shows the time of the 2nd wiping. The flowchart which shows the selection process of the wiping method. The flowchart which shows a 1st wiping process. The flowchart which shows a 2nd wiping process.

  Hereinafter, 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 kind of fluid ejecting apparatus will be described 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 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 pressurizing 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 pressurizing 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 pressurizing mechanism 30, the capping device 35, and the wiping device 36 are provided for each fluid ejecting head 24.

  The pressurizing mechanism 30 includes a rotating shaft 30a and a cam member 30b that rotates together with the rotating shaft 30a. The pressurizing mechanism 30 pressurizes the ink in the ink supply tube 27 and the fluid ejecting 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 pressurizing 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 with the wiper 44 in contact with the nozzle forming surface 24a, the lead screw 41 rotates, and the wiper 44 moves along with the support member 43 along the front-rear direction. Make sliding contact. 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 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 pressurizing 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 the atmospheric pressure and the ink pressure, and is disposed between the ink cartridge 26 and the pressurizing 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. The partial enlarged view of FIG. 5A shows the liquid level 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”). ing.

  In the 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 25 a and the vicinity of the center of the liquid level Sf is drawn into the nozzle 25. 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. For example, when the back pressure is increased from the steady state to a positive pressure, and the liquid level Sf bulges from the nozzle opening 25a as shown in FIG. If it is inside, the boundary of the liquid surface Sf can be kept in contact with the nozzle opening 25a.

  “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.

  Further, since the execution of the printing process involves the conveyance of the paper P, paper dust is often attached to the nozzle forming surface 24a and the like after the execution of the printing process. The paper P that has been cut to a predetermined size often has paper dust generated at the time of cutting attached to the edge that becomes the cutting part. This is because it scatters around it.

  Note that the paper dust refers to fiber fragments constituting the paper P, powders of contained substances and coating substances, and the like. For example, the paper P may contain or be coated with calcium carbonate as a pigment that produces whiteness, kaolin for producing gloss, or the like. And when calcium carbonate of these becomes paper powder, in the case of primary particles having a aggregate structure, the particle diameter is about 100 micrometers, but in the case of secondary particles with a collapsed aggregate structure, The particle size is about 10 micrometers. In contrast, since the nozzle opening 25a has a diameter of about 20 micrometers, fine calcium carbonate particles can enter the nozzle 25 through the nozzle opening 25a. If calcium carbonate enters the nozzle 25 and mixes with the ink, the viscosity of the ink increases remarkably, and there is a risk of causing severe clogging that is difficult to resolve.

  Further, during wiping, foreign matters such as paper dust and thickened ink enter the nozzle 25 with the wiper 44 attached, or the wiper 44 pushes the adhered material scraped from the nozzle forming surface 24a into the nozzle 25. There are times when At this time, if the back pressure is a negative pressure, the pushed-in foreign matter is taken into the ink in the nozzles, causing clogging, which may lead to missing dots.

  In this way, it can be said that dot missing due to wiping is more likely to occur as the back pressure is lower and 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, the CPU 150 performs any one of “first wiping performed by setting the back pressure to a positive pressure larger than atmospheric pressure” and “second wiping performed by setting the back pressure to a negative pressure lower than the atmospheric pressure”. One of the wiping operations is executed after a selection step for selecting the wiping method.

Next, as a wiping method selection step, a wiping method selection process by the CPU 150 will be described with reference to FIG.
As shown in FIG. 6, when the control device 100 receives a wiping execution command, the CPU 150 reads the operation history of the printer 11 stored in the nonvolatile memory 153 in step S11, and immediately before the printer 11 (before wiping is executed). ) Select the wiping method based on the action. Specifically, if the operation immediately before the printer 11 is cleaning (suction cleaning or pressure cleaning) in step S11, the CPU 150 selects the first wiping as the wiping method and proceeds to step S12. This is because there is a high possibility that foreign matter has adhered to the nozzle forming surface 24a after cleaning. In step S12, the CPU 150 ends the process after executing the first wiping.

  In step S11, if the operation immediately before the printer 11 is printing (printing process), the process proceeds to step S13, and the number of sheets P (number of printed sheets) N on which the CPU 150 has printed is a predetermined threshold value. It is determined whether or not it is Na or more. The threshold value Na is arbitrarily set based on experiments or the like, and is stored in the ROM 151 or the like.

  If the number of printed sheets N is greater than or equal to the threshold value Na in step S13, the CPU 150 selects the first wiping method as the wiping method and proceeds to step S12. This is because it is highly possible that paper dust has adhered to the nozzle forming surface 24a after printing a large number of sheets. In step S12, the CPU 150 ends the process after executing the first wiping.

  On the other hand, if the number of printed sheets N is less than the threshold value Na in step S13, the CPU 150 selects the second wiping method as the wiping method and proceeds to step S14. This is because when the number of printed sheets is small, the possibility that paper dust is attached to the nozzle forming surface 24a is low. In step S14, the CPU 150 ends the process after executing the second wiping.

Next, the first wiping execution process will be described with reference to FIG.
As shown in FIG. 7, first, as an ascending process in step S <b> 21, the CPU 150 drives the motor 48 of the elevating mechanism 38 in the forward direction to raise the wiper 44 to a position where it contacts the nozzle forming surface 24 a. Next, as a pressurizing step in step S22, the CPU 150 drives and controls the motor 46 of the pressurizing mechanism 30 in the forward direction to rotate the cam member 30b in the forward direction (clockwise direction in FIG. 5). As a result, the ink in the fluid ejecting head 24 is pressurized and the back pressure becomes positive.

  At the time of pressurization, as shown in FIG. 5B, the liquid surface Sf has a downwardly convex shape or the nozzle forming surface with the boundary of the liquid surface Sf clipped to the step of the nozzle opening 25a. It is preferable to have a planar shape that is substantially flush with 24a. 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.

  Here, 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, Sf has a planar shape with zero curvature. Further, when the back pressure is about −1 kPa, the probability of dot dropout is 80% or more, whereas when the back pressure is 0.3 to 1 kPa, the probability of dot dropout is reduced to about 20%. The experimental results are obtained. Furthermore, if the back pressure exceeds 3 kPa, the ink may drop from the nozzle opening 25a. Therefore, the back pressure during pressurization is preferably about 0 to 2 kPa.

  Next, as a sliding contact process (wiping process) in step S23, the CPU 150 drives and controls the motor 42 of the wiping device 36 to move the wiper 44 in the front-rear direction (a direction orthogonal to the paper surface in FIG. 5). Then, in the process in which the wiper 44 is in sliding contact with the nozzle formation surface 24a, the nozzle formation surface 24a is wiped while the nozzle formation surface 24a is wetted with the ink drawn from the nozzle 25 and the deposits are dissolved in the ink. Further, when the wiper 44 comes into contact with the liquid surface Sf, the back pressure is a positive pressure. Therefore, even when the wiper 44 moves in the front-rear direction at a high speed, the inside of the nozzle 25 is extracted as the wiper 44 draws out the ink. Ink is supplied promptly and contamination of the deposits into the nozzle 25 is suppressed.

  Next, as a pressurization releasing process in step S24, the motor 46 of the pressurizing mechanism 30 is driven and controlled in the reverse direction to rotate the cam member 30b in the opposite direction (counterclockwise direction in FIG. 5). . 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. As a result, the pressure is released and the back pressure returns to a negative pressure of about −1 kPa.

Finally, as a lowering step of step S25, the CPU 150 drives and controls the motor 48 of the lifting mechanism 38 in the reverse direction to lower the wiper 44 to the original position, and the process is finished.
Next, the second wiping execution process will be described with reference to FIG.

  As shown in FIG. 8, first, as an ascending step in step S31, the CPU 150 drives the motor 48 of the elevating mechanism 38 in the forward direction to raise the wiper 44 to a position where it contacts the nozzle forming surface 24a. Next, as a sliding contact process (wiping process) in step S32, the CPU 150 drives and controls the motor 42 of the wiping device 36 to move the wiper 44 in the front-rear direction (a direction orthogonal to the paper surface in FIG. 5). At this time, as shown in FIG. 5 (c), the liquid surface Sf in the nozzle 25 is in contact with the nozzle opening 25a at the boundary of the liquid surface Sf and the vicinity of the center of the liquid surface Sf is in the nozzle, as in the steady state. It has been pulled in. Therefore, in the process in which the wiper 44 is in sliding contact with the nozzle forming surface 24a, contact between the wiper 44 and the liquid surface Sf is suppressed.

  Finally, as the lowering step of step S33, 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) Since the back pressure of the liquid level Sf is larger than the atmospheric pressure during the first wiping, the ink is promptly supplied even if the wiper 44 comes into contact with the liquid level Sf and the ink is pulled out from the nozzle 25. In addition, mixing of foreign substances and the like is suppressed. Thereby, it is possible to suppress the occurrence of missing dots due to wiping. On the other hand, since the back pressure of the liquid level Sf is equal to or lower than the atmospheric pressure during the second wiping, even if the wiper 44 comes into contact with the liquid level Sf, the ink does not flow out from the nozzle 25 continuously. Therefore, by selectively executing one of the first wiping and the second wiping as necessary, it is possible to suppress the occurrence of dot omission while suppressing the consumption of ink accompanying the wiping.

  (2) Since the CPU 150 selects the wiping method based on the operation of the printer 11 before the wiping operation, it is possible to selectively execute either the first wiping or the second wiping according to the situation.

  (3) By selectively executing the first wiping after cleaning that is highly likely to have foreign matter attached to the nozzle forming surface 24a, it is possible to prevent foreign matter from entering the nozzle 25.

  (4) When the operation of the printer 11 before the wiping is a printing process and the number of printed sheets N (the number of conveyed sheets P) is equal to or greater than a predetermined threshold value Na, foreign matter is present on the nozzle forming surface 24a. There is a high possibility of adhesion. Therefore, by selectively executing the first wiping, it is possible to suppress foreign matter from entering the nozzle 25. On the other hand, when the number N of printed sheets before the wiping is less than the threshold value Na, there is a low possibility that foreign matter has adhered to the nozzle forming surface 24a. Therefore, the second wiping is selectively executed to perform wiping. Concomitant ink consumption can be suppressed.

(5) Since either the first wiping or the second wiping is selected as the wiping method in the selection step, appropriate wiping can be executed according to the situation.
The above embodiment may be changed to another embodiment as described below.

  The CPU 150 may select one of the first wiping performed by setting the back pressure to be equal to or higher than the atmospheric pressure and the second wiping performed by setting the back pressure to be lower than the atmospheric pressure as the wiping method.

  According to this configuration, since the back pressure of the liquid level Sf is equal to or higher than the atmospheric pressure at the time of the first wiping, even if the wiper 44 comes into contact with the liquid level Sf and the ink is pulled out from the nozzle 25, the ink is quickly discharged. While being supplied, mixing of foreign matters and the like is suppressed. Thereby, it is possible to suppress the occurrence of missing dots due to wiping. On the other hand, since the back pressure of the liquid level Sf is smaller than the atmospheric pressure during the second wiping, the ink does not continuously flow out from the nozzle 25 even if the wiper 44 contacts the liquid level Sf. Therefore, by selectively executing one of the first wiping and the second wiping as necessary, it is possible to suppress the occurrence of dot omission while suppressing the consumption of ink accompanying the wiping.

  The CPU 150 selects the first wiping when the operation immediately before the printer 11 is printing (fluid ejection), while selecting the second wiping when the operation immediately before the printer 11 is not printing. You may make it do.

  In this case, after printing, there is a high possibility that foreign matter has adhered to the nozzle forming surface 24a due to the conveyance of the paper P. Therefore, by selectively executing the first wiping, the foreign matter into the nozzle 25 is removed. Mixing can be suppressed. On the other hand, since it is unlikely that foreign matter has adhered to the nozzle forming surface 24a before printing, the consumption of fluid associated with wiping can be suppressed by selectively executing the second wiping.

When the paper P is a long paper, the length of the transported paper P may be set as a threshold in step S13.
The wiping method may be selected depending on the type of medium that receives the fluid. For example, the second wiping may be selected when a film that hardly generates paper dust or the like is used as the medium. Alternatively, the first wiping may be selected when glossy paper containing a large amount of calcium carbonate or the like or paper with high whiteness is used as the medium.

  -If the transport speed of the paper P is high, paper dust or the like is likely to scatter. Therefore, when the transport speed of the paper P is equal to or higher than a predetermined threshold, the first wiping is selected, while the transport speed of the paper P is The second wiping may be selected when it is less than a predetermined threshold.

  -As a wiping method, you may enable it to select the 3 or more wiping methods from which back pressure differs. In this case, it is preferable to change the back pressure in a plurality of stages in accordance with the threshold (number of printed sheets, transport speed, etc.), the type of medium, and the like. The applied pressure for changing the back pressure can be adjusted by the rotation angle of the cam member 30b.

The first wiping may be selected when wiping is performed at high speed, while the second wiping may be selected when wiping is performed at low speed.
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 pressurizing 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, when the pressurization mechanism 30 performs pressurization, the on-off valve is closed, so that the applied pressure can be prevented from reaching the upstream side, and the applied pressure can be concentrated on the downstream side.

-The back pressure during the second wiping may be lower than the steady state. In this case, the contact between the wiper 44 and the liquid level Sf can be further suppressed.
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 employ | adopt the pressurization mechanism provided with the piezoelectric element, the pump, the piston. 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 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 pressurizing mechanism 30 is provided in a single fluid supply path (ink supply tube 27) connected to the ink cartridge 26. Alternatively, the pressurizing 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 ejection apparatus, 12 ... Conveyance mechanism, 24 ... Fluid ejection head, 24a ... Nozzle formation surface, 25 ... Nozzle, 25a ... Nozzle opening, 44 ... Wiper, 150 ... CPU functioning as selection means, Na ... Threshold value, P: paper as medium, Sf: liquid level.

Claims (5)

A fluid ejecting head provided with a nozzle for ejecting fluid;
A wiper for wiping a nozzle forming surface in which a nozzle opening of the nozzle is formed in the fluid ejecting head;
The first wiping performed by making the pressure of the fluid in the fluid ejecting head, which is the back pressure of the liquid level formed in the nozzle, larger than the pressure of the gas in contact with the liquid level and the back pressure below the pressure Selecting means for selecting one of the second wiping methods performed as a wiping method ;
The selection unit selects the first wiping when the operation before performing the wiping is cleaning that forcibly discharges the fluid in the nozzle from the nozzle opening. . A transport mechanism for transporting the medium that receives the fluid;
The selection unit selects the first wiping when the transport amount of the medium before the wiping is performed is equal to or greater than a predetermined threshold, while the transport amount of the medium before the wiping is the threshold. 2. The fluid ejecting apparatus according to claim 1, wherein the second wiping is selected when the number is less than the second wiping. The selecting means selects the first wiping when the operation before performing the wiping is the ejection of the fluid, and selects the first wiping when the operation before performing the wiping is not the ejection of the fluid. The fluid ejecting apparatus according to claim 1 , wherein two wiping is selected. A fluid ejecting head provided with a nozzle for ejecting fluid;
A wiper for wiping a nozzle forming surface in which a nozzle opening of the nozzle is formed in the fluid ejecting head;
First wiping performed by setting the pressure of the fluid in the fluid ejecting head, which is the back pressure of the liquid level formed in the nozzle, to be equal to or higher than the pressure of the gas in contact with the liquid level, and the back pressure is made smaller than the pressure. Selecting means for selecting one of the second wiping performed as a wiping method ,
The fluid jet is characterized in that the selection means selects the first wiping when the operation before the wiping is cleaning that forcibly discharges the fluid in the nozzle from the nozzle opening. apparatus. 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,
The first wiping performed by making the pressure of the fluid in the fluid ejecting head, which is the back pressure of the liquid level formed in the nozzle, larger than the pressure of the gas in contact with the liquid level and the back pressure below the pressure A selection step of selecting one of the second wiping methods performed as the wiping method ;
The wiping method of selecting the first wiping in the selection step when the operation before the wiping is cleaning for forcibly discharging the fluid in the nozzle from the nozzle opening .

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