JP4543719B2 - Liquid ejection device and method for driving liquid ejection device - Google Patents

Description

The present invention relates to a liquid ejecting apparatus and a method for driving the liquid ejecting apparatus, and in particular, a droplet ejected from a nozzle by providing a plurality of pressure variable elements in one liquid chamber and changing the balance of driving of the plurality of pressure variable elements. It can be applied to a printer or the like that changes the direction of the image. The present invention can prevent wasteful consumption of ink and the like and reliably prevent nozzle clogging by changing the direction of random ejection during preliminary ejection to eject liquid droplets. Like that.

  2. Description of the Related Art Conventionally, in an inkjet printer, a desired image or the like is printed by ejecting ink droplets from nozzles provided in a printer head and attaching them to paper.

  In such an ink jet printer, for example, compared with a laser printer or the like, it is easy to downsize and has a low running cost. As the volatile components evaporate from the ink remaining in the ink, these inks thicken and solidify, which may clog the so-called nozzles and make it difficult to eject ink droplets normally.

  For this reason, conventionally, in this type of printer, a cleaning process is executed at the start of printing or the like, thereby preventing image quality deterioration. Here, this cleaning process is performed by, for example, removing the ink remaining on the nozzle by so-called preliminary discharge after wiping off and removing the thickened and solidified ink from the side surface of the nozzle opening with a blade made of hard rubber or the like. It is made like that.

  Regarding the removal by such a blade, Japanese Patent Application Laid-Open No. 57-34969 discloses that the blade is moved while rotating a rotating body provided with a plurality of such blades to increase the viscosity and solidify more reliably. There has been proposed a method for removing the ink. In addition, the preliminary ejection is performed by ejecting ink droplets toward a cap for receiving waste ink, for example.

Also in this type of printer, one provided with a plurality of pressure variable elements in the liquid chamber, the method of Ru by changing the direction of the droplet flying out from the nozzle by Rukoto alter the balance of driving of the plurality of pressure variable elements ( Hereinafter, it is called a variable discharge direction method). According to this ejection direction variable method, it is possible to perform printing normally by ejecting ink droplets from adjacent nozzles instead of nozzles that have made it difficult to eject ink droplets. Deterioration in image quality due to clogging can be prevented more reliably than in the past. Even when the nozzle formation position varies somewhat, it is possible to obtain a high-quality printing result by correcting the ejection direction.

However, when the direction of the ink droplet is changed by the variable ejection direction method, as shown in FIG. 14, the ejection amount of the ink droplet decreases as the ejection direction inclines from the front direction of the nozzle. In this way, when preliminary ejection is performed with the ejection direction corrected, most of the nozzles can completely eject the ink remaining in the nozzles, whereas the specific nozzles cannot completely eject the remaining ink. There is.

As a method of solving this problem, a method of increasing the number of ink discharges in preliminary discharge and completely discharging remaining ink from a nozzle having a small ink discharge amount can be considered. A large amount of nozzles consumes ink wastefully. However, although such wasteful ink consumption is very small for one nozzle, for example, in a full-line type printer, the number of nozzles is so large that it cannot be ignored. Become.
JP 57-34969 A

  The present invention has been made in consideration of the above points, and even when droplets are ejected by the variable ejection direction method, it is possible to prevent wasteful ink consumption and prevent nozzle clogging reliably. The present invention is intended to propose a liquid ejection device that can be used and a method for driving the liquid ejection device.

In the invention of claim 1 for solving the above problems, the pressure variable element for changing the pressure in the liquid chamber is provided two in one liquid chamber, by driving the two pressure variable element, and held in the liquid chamber Liquid discharge that changes the direction in which the liquid drop pops out by causing the liquid drop to jump out of the nozzle toward the target of the liquid drop, and by varying the energy for driving the two pressure variable elements in the liquid chamber. Applies to equipment. In the present invention, after the liquid remaining in the nozzle is discharged from the nozzle by the preliminary discharge process, the liquid droplet is ejected toward the processing target, and the liquid discharge by the preliminary discharge process is A process of ejecting the droplets from the nozzles is performed by randomly changing the droplet ejection direction.

In the invention of claim 6, the pressure variable element for changing the pressure in the liquid chamber is provided two in one liquid chamber, by driving the two pressure variable element, the droplets of liquid held in the liquid chamber A liquid ejecting apparatus driving method for changing the direction in which droplets are ejected by ejecting them from a nozzle toward a droplet processing target and by varying the energy for driving the two pressure variable elements in the liquid chamber. Apply. In the present invention, after the liquid remaining in the nozzle is discharged from the nozzle by the preliminary discharge process, the liquid droplet is ejected toward the processing target, and the liquid discharge by the preliminary discharge process is The direction in which the droplets are ejected is randomly changed to eject the droplets from the nozzles.

The arrangement of claim 1, the pressure variable element for changing the pressure in the liquid chamber is provided two in one liquid chamber, by driving the two pressure variable element, the droplets of liquid held in the liquid chamber, the liquid pops out from the nozzle toward a processing target by the droplets, more changing the balance of driving of the plurality of pressure variable elements, it applied to a liquid ejecting apparatus changes direction jumping out of the droplet. In the present invention, after the liquid remaining in the nozzle is discharged from the nozzle by the preliminary discharge process, the droplet is ejected toward the processing target, and the discharge of the liquid by the preliminary discharge process randomly determines the direction in which the liquid droplet is ejected. If the process is changed so that the droplets are ejected from the nozzle, even if the amount of droplets varies from nozzle to nozzle, this variation can be reduced and the preliminary ejection process can be executed. This makes it possible to prevent the nozzles from being clogged reliably.

  Thus, according to the configuration of the sixth aspect, it is possible to provide a driving method of the liquid discharge apparatus that can prevent wasteful consumption of ink or the like and reliably prevent nozzle clogging.

  According to the present invention, it is possible to prevent wasteful consumption of ink or the like and reliably prevent nozzle clogging.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

(1) Configuration of Embodiment FIG. 2 is a perspective view showing a line printer according to the present invention, and FIG. 3 is a sectional view of the line printer shown by cutting FIG. 2 along the line AA. The line printer 1 is a full line type line printer, and a printer main body 2 is formed in a substantially rectangular shape. The line printer 1 is configured to feed the paper 3 by mounting a paper tray 4 containing the paper 3 to be printed from a tray inlet / outlet formed on the front surface of the printer body 2.

  In the line printer 1, when the paper tray 4 is attached to the printer main body 2 from the tray entrance and the printing is instructed by the user, the printer main body 2 is rotated by the rotation of the paper feed roller 5 provided in the printer main body 2. The sheet 3 is fed out from the sheet tray 4 toward the back side of the printer, and the feeding direction of the sheet 3 is switched to the front direction by the reverse roller 6 provided on the back side of the printer body 2. In the line printer 1, the sheet 3 having the sheet feeding direction switched to the front direction is conveyed by the conveying belt 7 so as to cross the sheet tray 4, and is discharged from the discharge port disposed on the front side of the line printer 1. It is discharged to the tray 8. As a result, the line printer 1 forms a transport mechanism for the paper 3, and feeds and transports the paper 3 by driving the paper supply and discharge motors that drive the rollers 5, 6 and the transport belt 7 constituting the transport mechanism. It is designed to be discharged. Here, as indicated by an imaginary line in FIG. 3, the entire conveying belt 7 is located at a predetermined retraction position on the paper 3 side with the rotation axis of the roller 7 </ b> A provided on the reversing roller 6 side as the rotation center. It is formed so as to be able to rotate, and is held in this retracted position except during printing.

  In the line printer 1, an upper lid 10 is provided on the upper end surface, and the head cartridge 11 is disposed so as to be replaceable as indicated by an arrow B in the middle of the upper lid 10 and in the middle of paper conveyance in the front direction.

  Here, the head cartridge 11 is a full-line type printer head of four colors of yellow, magenta, cyan, and black, and ink tanks 12Y, 12M, 12C, and 12K for each color are provided on the upper side. The head cartridge 11 is provided on the side of the paper 3 of the head assembly 13 which is an assembly of printer heads related to the ink tanks 12Y, 12M, 12C and 12K, and is provided in the head assembly 13 when not in use. And a head cap 14 that closes the nozzle array and prevents the ink from drying. As a result, in the line printer 1, the head cap 14 is moved to expose the paper side surface of the head assembly 13, and then the ink droplets of each color are attached to the paper 3 by driving the head assembly 13 to obtain a desired image. Etc. can be printed in color.

  That is, as shown in a partial cross section in FIG. 4, the head assembly 13 has an end surface on the head cap 14 side formed by a nozzle sheet 22 in which a row of nozzles 21 corresponding to each ink is formed according to the paper width. Thus, when the head cap 14 is moved to expose the sheet side surface of the head assembly 13, the rows of the nozzles 21 are formed to be exposed.

  The head cap 14 is formed with a case 23 in a box shape formed by forming a wall surface around a hard resin material or the like. As shown in FIG. 5A, the head cap 14 is formed so that the case 23 completely closes the sheet side surface of the head assembly 13 in a state where the transport belt 7 is retracted to the retracted position. The evaporation of the ink component from the ink can be reduced.

  Further, the head cap 14 moves to the front side of the printer 1 along the sheet side surface of the head assembly 13 as shown by an arrow C in FIG. 5B by driving a cap opening / closing motor provided in the printer main body 2. Thus, the nozzle 21 can be exposed during printing. FIG. 5C is a diagram showing a state in which the head cap 14 has moved to the front side to the end. In the printer 1, when the movement of the head cap 14 is completed in this way, the transport belt 7 is moved to the retracted position. Further, the paper 3 is rotated to a printable position and conveyed by the head assembly 13 so as to be printable.

  The head cap 14 is provided with a cleaning mechanism for the head assembly 13 inside. That is, as shown in FIGS. 6A and 6B, the head cap 14 is provided with a cleaning roller 25 rotatably on the inner back surface side, and the arrow D is moved by the movement of the head assembly 13 along the paper side surface. As shown in FIG. 8, the cleaning roller 25 is pressed against the nozzle sheet 22 and rotates.

  Here, the cleaning roller 25 is a cleaning member that removes ink residue adhering to the nozzle sheet 22 including the tip portion of the nozzle 21, and has elasticity and a porous material that can sufficiently absorb ink, It is formed by at least the length of the nozzle row. Specifically, the cleaning roller 25 is formed of, for example, sponge or felt. Accordingly, as shown in FIG. 7, the cleaning roller 25 absorbs and removes the liquid component from the ink residue 26 attached to the paper side surface of the nozzle sheet 22. Of such ink residue 26, the ink residue thickened on the nozzle sheet 22 by evaporation of volatile components and the ink residue adhered and solidified on the nozzle sheet 22 are peeled off from the nozzle sheet 22 and removed. It is made like that. As shown in FIG. 6A, when the nozzle 21 is traversed, the ink 26 is also absorbed from the nozzle 21 by capillary action, thereby reducing the amount of ink remaining in the nozzle 21. When the cleaning roller 25 is formed of a porous member, the ink residue is absorbed more efficiently by absorbing the ink when the portion deformed by pressing against the nozzle sheet 22 returns to its original shape by rotation. Can be removed.

  The cleaning roller 25 is held by the head cap 14 so as to be movable in the vertical direction. When the head cap 14 is moved to expose the nozzle 21, the cleaning roller 25 is pressed by the nozzle sheet 22, but this is not the case. When the exposure of the nozzle 21 is stopped, it is held so as not to contact the nozzle sheet 22. Thus, in this embodiment, the nozzle sheet 22 is not cleaned at the end of printing.

  Further, the head cap 14 is provided with a scraper 27 on the front side of the cleaning roller 25. Here, the scraper 27 is formed of, for example, hard rubber and is provided so as to contact the cleaning roller 25. As a result, the scraper 27 scrapes off the ink residue adhering to the cleaning roller 25 from the cleaning roller 25 and keeps the cleaning roller 25 in a clean state.

  Further, the head cap 14 is formed with an area AR in which the bottom surface is exposed between the back surface side and the wall surface of the cleaning roller 25, and this area AR is assigned as a preliminary discharge area, and this area crosses under the nozzle 21. At the timing, the corresponding nozzles are preliminarily ejected, and ink droplets related to the preliminary ejection are received in this area AR.

  Further, the head cap 14 is provided with a hygroscopic sheet material 28 that absorbs ink over almost the entire bottom surface including the preliminary ejection area AR. The sheet material 28 is formed of, for example, a sponge. As a result, the head cap 14 absorbs ink droplets related to the preliminary discharge by the sheet material 28, and prevents the ink related to the preliminary discharge, and further, the ink received to the inside from splashing back to the nozzle sheet 22 side. It is made to do. Further, by replacing the sheet material 28, so-called waste ink can be easily removed.

  Accordingly, as shown in FIG. 8, the head cartridge 11 starts from the state in which the head cap 14 covers the nozzle 21 (FIG. 8A), as indicated by an arrow E, by the start of printing. (FIG. 8B), and a cleaning process is executed during this movement. Further, with the head cap 14 completely moved to the front side (FIG. 8C), an image or the like is printed, and the head cap 14 is moved to the original position as indicated by an arrow F upon completion of printing. The nozzle 21 is prevented from being exposed (FIGS. 8D and 8E).

  In this way, the printer 1 is provided with a plurality of photoelectric switches for detecting the position of the head cap 14 by moving the head cap 14 to the front side of the printer 1 at the start of printing. In addition, it is possible to detect the state in which the preliminary discharge area AR is positioned directly below the nozzles 21 of the respective colors.

  FIG. 9 is an exploded perspective view showing the head assembly 13 by enlarging a portion related to ejection of ink droplets as viewed from the paper 3 side. The head assembly 13 is formed by attaching a head chip 31 to a nozzle sheet 22 held in a predetermined frame and holding it in a case.

  Here, the nozzle sheet 22 is a sheet-like member in which rows of nozzles 21 having paper widths respectively corresponding to yellow, magenta, cyan, and black inks are arranged side by side. In this embodiment, nickel containing cobalt is formed by electroforming. It is made of material.

  On the other hand, the entire head chip 31 is formed in a rectangular shape when viewed from the nozzle sheet 22 side by a semiconductor substrate formed with the partition 33 of the ink liquid chamber 32. In the head chip 31, the partition 33 of the ink liquid chamber 32 is formed in a comb tooth shape corresponding to each nozzle 21 provided on the nozzle sheet 22 so that one side of the long side of the rectangular shape is open. . A set of heating elements 34A and 34B is sequentially provided at a predetermined pitch in each ink liquid chamber 32 corresponding to each nozzle 21, and a drive circuit for driving the set of heating elements 34A and 34B is formed. The Thus, the head chip 31 is affixed to the nozzle sheet 22 to form the ink liquid chamber 32, and the corresponding ink tanks 12Y are respectively formed by the ink flow paths formed along one side where the heating elements 34A and 34B are provided. , 12M, 12C, and 12K inks can be guided to the ink liquid chambers 32. Further, a set of heat generating elements 34A and 34B provided in each ink liquid chamber 32 is driven by a corresponding drive circuit to heat the ink in each ink liquid chamber 32 to generate bubbles, and the pressure caused by the bubbles increases. Ink droplets can be ejected from the corresponding nozzles 21.

  The head chip 31 is actually scribed on each chip after a drive circuit for a plurality of chips, heating elements 34A and 34B, and a partition wall 33 for the ink liquid chamber are formed on the semiconductor wafer, and then the nozzle sheet 22 is pasted. It is made to be created efficiently by this.

As shown in a plan view and a cross-sectional view in FIG. 10, in each ink liquid chamber 32, a pair of heating elements 34 </ b> A and 34 </ b> B having substantially the same shape and the same resistance value are arranged side by side in the direction in which the nozzles 21 are arranged. The FIG. 10A is a plan view showing a state in which the nozzle sheet 22 is removed. As a result, in the head assembly 13, the ink droplet ejection direction can be changed with respect to the arrangement direction of the nozzles 21 by controlling the driving of the heating elements 34 </ b> A and 34 </ b> B that are pressure variable elements that change the pressure of the ink liquid chamber 32. It is made so that.

  FIG. 11 is a connection diagram for explaining the principle of drive control of the heating elements 34A and 34B. The head assembly 13 is connected to the heat generating elements 34A and 34B by a predetermined wiring pattern, thereby forming a series circuit of the heat generating elements 34A and 34B. In the head assembly 13, one end of the series circuit including the heat generating elements 34 </ b> A and 34 </ b> B is connected to the main control circuit 41, and the other end is connected to the power source 42. Here, the main control circuit 41 is a drive circuit that drives the series circuit of the heating elements 34A and 34B at the timing of ejecting the ink droplets. One end of the series circuit by the heating elements 34A and 34B is connected via the switch circuit 44. Ground.

In the head assembly 13, the connection midpoint between the heat generating elements 34 </ b> A and 34 </ b> B is connected to the sub-control circuit 45. Here, the sub control circuit 45 changes the driving balance of the heating elements 34A and 34B by the main control circuit 41 in accordance with the direction in which the ink droplets are ejected. That is, the sub-control circuit 45 switches the contact of the selector 46 according to the direction in which the ink droplets are ejected, thereby changing the driving balance of the heating elements 34A and 34B. In this embodiment, such balance control is performed by switching between the inflow and outflow of current to the connection midpoint of the heating elements 34A and 34B, and further by changing the current value to be inflowed and outflowed. However, it can also be executed by changing the potential at the midpoint of connection instead of these.

In FIG. 11, such a potential and current variable mechanism is constituted by a selector 46, a power supply 47, and resistors 48A to 48D. That is, when the resistor 48A or 48B connected to the power source 47 is selected, the selector 46 generates a current determined by the resistance value of the heating elements 34A and 34B, the resistor 48A or 48B and the voltage of the power source 47, and the connection of the heating elements 34A and 34B. Let it flow into the midpoint. When a contact point that is not connected at all is selected, the change in the balance of the heating elements 34A and 34B is stopped. When the grounded resistors 46C and 46D are selected, a current determined by the resistance values of the heat generating elements 34A and 34B and the resistors 46C or 46D flows out from the connection midpoint of the heat generating elements 34A and 34B. Thus, in this embodiment is made so that changing efficiently heating elements 34A, the balance of driving of 34B by the sub-control circuit 45.

  FIG. 12 is a connection diagram showing a specific configuration of the main control circuit 41 and the sub control circuit 45. The main control circuit 41 grounds the other ends of the heat generating elements 34A and 34B to which the power source 42 is connected by a constant current circuit 51 using a MOSFET, and this constant control signal SC1 through an AND circuit 52 having an inverter circuit configuration. The operation of the current circuit 51 is controlled. Here, the signal level of the control signal SC1 rises at the timing when ink droplets are ejected from the nozzles 21 to which the main control circuit 41 is assigned in correspondence with the paper feed, and thereby the heating element 34A, A series circuit 34B is driven by a power source 42.

  The sub-control circuit 45 includes power supply circuits 55A, 55B, 55C, and 55D that allow a predetermined current to flow into the connection midpoints of the heat generating elements 34A and 34B, and to discharge a predetermined current from the connection midpoint. . Here, in the power supply circuits 55A, 55B, 55C, and 55D, the value of the current flowing into the connection middle point or the value of the current flowing out from the connection middle point is 4: 2: 1 depending on the setting of the built-in constant current circuit. 1 and the same configuration except that the control signals SA, SB, SC, SD are set to control the SA, SB, SC, SD, respectively, except that the current elements bias the driving of the heating elements 34A, 34B. In the following description, the power supply circuit 55A will be described in detail.

  Therefore, in this embodiment, the current values of the power supply circuits 55A, 55B, 55C, and 55D are set to 4: 2: 1: 1, so that the power supply circuits 55A, 55B, and 55C have a current value of 2. The power is changed stepwise by the power, and thereby the driving of the heating elements 34A and 34B is efficiently biased with a simple configuration as a whole.

  Here, in this embodiment, the control signals SA, SB, SC, SD are set so that the ink droplets ejected from the nozzles 21 have a predetermined pitch, and thereby various errors such as mounting errors when the head chip 31 is mounted. Thus, the deviation of the ink adhesion position due to the manufacturing variation is corrected, and as a result, a higher quality printing result is output as compared with the conventional case.

  Thus, the power supply circuit 55A uses the exclusive NOR circuit to switch the direction switching signal SC3 for switching between the inflow of the current to the connection midpoint of the heating elements 34A and 34B and the outflow of the current from the connection midpoint. 57, whereby the polarity of the control signal SA is switched by this direction switching signal SC3. The power supply circuit 55A directly inputs the output signal of the exclusive NOR circuit 57 to the AND circuit 59, and inverts the polarity via the inverter circuit 60 and inputs it to the AND circuit 61. The AND circuits 59 and 61 respectively gate the output signal of the exclusive NOR circuit 57 and the output signal of the inverter circuit 60 by the control signal SC1 and output them to the MOSFETs 62 and 63, thereby generating the heating elements 34A and 34B by the control signal SC1. During the period of driving, the MOSFETs 62 and 63 are complementarily controlled according to the direction switching signal SC3 and the control signal SA.

  Further, the power supply circuit 55A controls the on / off of the constant current circuit 58 by the MOSFET by a control signal SC2 as to whether or not the driving of the heating elements 34A, 34B is biased. In the power supply circuits 55A to 55C, the current value for biasing the driving of the heat generating elements 34A and 34B is set to 4: 2: 1: 1 by the setting of the constant current circuit 58, respectively.

  The MOSFETs 62 and 63 receive the constant current circuit 58 at their sources, and the drains of the MOSFETs 62 are connected to the connection midpoints of the heating elements 34A and 34B. The drain of the MOSFET 63 is connected to a current mirror circuit formed of MOSFETs 64 and 65 provided on the power supply side, and a constant current equal to the current value of the constant current circuit 58 is applied to the heating elements 34A and 34B by the MOSFET 65. Let it flow into the midpoint of connection. As a result, the MOSFETs 62 and 63 are complementarily turned on and off in accordance with the direction switching signal SC3 and the control signal SA during the period in which the heating elements 34A and 34B are driven by the control signal SC1. In a constant current circuit 58, when the drive of the heating elements 34A and 34B is biased by operating according to the control signal SC2, and when the current flows out from the midpoint of connection, the MOSFET 62 side is turned on. Instead, the current from the constant current circuit 58 is sucked, and conversely, when the current is allowed to flow into the connection midpoint, the MOSFET 63 side is switched to the on state so that the current from the constant current circuit 58 flows out. As a result, the nozzle 2 by the heating elements 34A and 34B For, it is configured so as to be able to control the ejection direction of ink droplets.

  FIG. 13 is a block diagram showing the configuration of the printer 1. In the printer 1, an interface (I / F) 71 inputs and outputs various commands related to printing, status information, print data used for printing, and the like with a host device such as a computer. The mechanical drive unit 72 drives the drive mechanism of the printer 1 under the control of the control unit 73. Specifically, the cap opening / closing motor 74 that moves the head cap 14, the rollers 5 and 6 constituting the transfer mechanism, and the transfer The feeding and discharging motor 75 for the belt 7 and a motor for rotating the conveying belt 7 are driven. The photoelectric switch 79 detects the movement of the ejection area AR <b> 1 below the nozzles 21 for each color in the preliminary ejection area AR due to the movement of the head cap 14.

  The head drive unit 76 is an electrothermal conversion unit for each color and a plurality of main control circuits 41 and corresponding sub-control circuits 45 related to the heating elements 34A and 34B that are variable pressure units for each ink chamber. The control signal SC1, SC2, SA to SD, the interface of the direction switching signal SC3 to the circuit 41 and the sub-control circuit 45, the interface with the mechanical drive unit 72, and the like. Ink droplets are ejected from the nozzle 21 in a desired direction.

  The control unit 73 controls the overall operation of the printer 1 by executing the processing program recorded in the read-only memory (ROM) 77 by the central processing unit (CPU) 78, and prints by print data input from the host device. And the cleaning process is executed. As a result, although this processing program is installed and provided in the printer 1 in advance, it can be replaced by downloading via a network such as the Internet instead of such prior installation. Alternatively, it may be provided by a recording medium. In such a recording medium, various recording media such as a memory card, an optical disk, and a magnetic disk can be widely applied.

  That is, FIG. 1 is a flowchart showing the processing procedure of the central processing unit 78. When printing is instructed from the host device, the central processing unit 78 starts this processing procedure and proceeds from step SP1 to step SP2. Here, the central processing unit 78 starts the movement of the head cap 14 from the state in which the nozzle 21 of the nozzle sheet 22 is blocked by the start of driving of the cap opening / closing motor 74 via the mechanical drive unit 72, and the cleaning by the cleaning roller 25. To start.

  Subsequently, the central processing unit 78 proceeds to step SP3, and determines whether or not the head cap 14 has moved to the preliminary discharge position by determining whether or not the discharge area AR1 has moved below the nozzles 21 of each color by the photoelectric switch 79. If a negative result is obtained here, step SP3 is repeated. As a result, the central processing unit 78 waits for the discharge area AR1 of the head cap 14 to be positioned below the nozzle 21 after starting the movement of the head cap 14. When the discharge area AR1 is positioned below the nozzle 21, an affirmative result is obtained in step SP3, and the process proceeds to step SP4, where the corresponding color nozzle 21 is preliminarily discharged.

In this preliminary discharge, the central processing unit 78 discharges ink droplets a predetermined number of times by randomly changing the discharge direction. In this embodiment, as described above, the angle of the discharge direction is switched by the control signals SA to SD, and the angle of the discharge direction is switched to 15 sides by switching the discharge direction by the direction switching signal SC3. On both sides, the discharge direction can be switched in 30 steps. If the case where the discharge direction is not changed is added to this, the discharge direction of one nozzle 21 can be switched among 31 types.

As a result, the central processing unit 78 generates control signals SC2, SA to SD, and direction switching signals by generating a random number for each ejection of each ink droplet so that these 31 types of ejection directions are selected with equal occurrence probability. SC3 is set, thereby changing the ejection direction randomly. Here, when the ink droplets are ejected in the front direction of the nozzle 21, that is, in the extension direction of the tube axis of the nozzle 21, the amount of the ink droplet is the largest, and gradually decreases as the ejection direction is inclined from the front direction. To do. As a result, even when the discharge amount of one ink droplet varies at each nozzle 21, when the ink droplet is discharged a predetermined number of times by changing in the random discharge direction in this way, The total amount of ink droplets ejected from each nozzle 21 is averaged and variation is reduced. Thereby, in this embodiment, the variation in the discharge amount in the preliminary discharge is reduced.

  When ink droplets are ejected in various directions in this way, the ink remaining in the ink liquid chamber can be agitated as compared with the case where ink droplets are ejected in a certain direction. As a result, in the printer 1, for example, when the ink density is high near the nozzle due to nonuse for a long period of time, even if the ink having such high density is not ejected from the nozzle, The ink density can be made uniform in the ink liquid chamber, thereby further preventing unnecessary ink consumption and improving the printing quality.

  Further, in this preliminary discharge, after the ink remaining on the nozzle 21 is sucked by the cleaning roller 25, the ink droplets are discharged in an amount sufficient for discharging the previous ink remaining on the nozzle 21. Has been made. Accordingly, in the printer 1, volatile components are evaporated from the ink, and the highly viscous ink remaining in the nozzle 21 is completely discharged from the nozzle 21.

  When the processing of step SP4 is completed in this way, the central processing unit 78 moves to step SP5, determines whether or not the preliminary ejection processing has been completed for all inks, and if a negative result is obtained here, The process returns to step SP3. As a result, the central processing unit 78 repeats the processing procedure of steps SP3-SP4-SP5-SP3 for each of the inks on the front side from the ink provided on the back side of the printer 1 and thereby reserves the nozzles 21 for each ink. A discharge process is executed.

  When the preliminary ejection is completed for all inks, the central processing unit 78 moves from step SP5 to step SP6. Here, based on the detection result of the photoelectric switch 79, it waits for the head cap 14 to move to the printing position, and then the transport belt 7 is rotated from the retracted position to the printing position. When these processes are completed, the host device is notified of the completion of print preparation via the interface 71, and the mechanical drive unit 72 and the head drive unit 76 are driven by the print data sequentially input from the host device by this notification. Execute the printing process.

  At this time, the central processing unit 78 outputs the control signals SA to SD, SC2, and SC3 to the sub control circuit 45 by recording the correction data table held in the built-in memory. Correct the droplet ejection direction. In this embodiment, by correcting the ink ejection direction by recording in the correction data table, the vertical portion of printing that each nozzle 21 is responsible for is replaced with the adjacent nozzle 21, and the same nozzle 21 is moved vertically. Image quality deterioration due to printing of the same portion is effectively avoided. Such image quality degradation is a phenomenon that is observed as a weak vertical stripe pattern when a large area is printed with a specific color ink.

  When printing is performed in this manner, the central processing unit 78 moves to step SP7, waits for a subsequent printing instruction for a predetermined time, and instructs the printing again from the host device during this waiting period. Then, the process returns to step SP6. On the other hand, if printing is not instructed after waiting for a predetermined time, the central processing unit 78 moves from step SP7 to step SP8, moves the conveyor belt 7 to the standby position, and then drives the cap opening / closing motor 74. The head cap 14 is moved to close the nozzle 21, and the process proceeds to step SP9 to end this processing procedure.

(2) Operation of Embodiment In the above configuration, the printer 1 uses the print data supplied from the host device to transfer the ink droplets from the head cartridge 11 while conveying the paper 3 to be processed by a predetermined paper feed mechanism. The ink droplets adhere to the paper 3 being transported, whereby an image, text, etc. are printed according to the driving of the head cartridge 11 (FIG. 1).

In the printer 1, nozzle rows for yellow, magenta, cyan, and black are sequentially formed on the nozzle sheet 22 that is a sheet-like member according to the paper width, and each nozzle 21 in the nozzle row is used for printing. Ink droplets pop out (FIG. 9). In each nozzle 21, heating elements 34A and 34B as pressure variable elements that increase the pressure of the ink liquid chamber are provided in the corresponding ink liquid chamber in the extending direction of the nozzle row. these heating elements 34A, is to balance the drive change in 34B, the direction of jumping out of the ink droplets is varied in the arrangement direction of the nozzles 21, by this change, adjacent longitudinal portions of the printing to each nozzle 21 is responsible Thus, a desired image or the like can be printed with high image quality.

  Thus, by repeating printing, in the printer 1, ink droplets ejected from the nozzles 21 adhere to the nozzle sheet surface. On the opening side of the nozzle 21, it becomes wet with ink, and the ink remains inside the nozzle 21.

  In the printer 1, in the case of the droplets adhering to the nozzle sheet surface and the ink that wets the opening side of the nozzle 21, the volatile component of the ink gradually evaporates, the viscosity gradually increases, and finally the solid It becomes a state stuck to the nozzle sheet 22. Further, even in the ink remaining inside the nozzle, the viscosity gradually increases. As a result, the nozzle 21 is finally clogged and printing cannot be performed normally.

  Therefore, in this embodiment, when printing is not performed, the conveyance belt 7 that conveys the paper 3 is retreated to a retreat position that is a position away from the nozzle 21 (FIGS. 3 and 5). In the space formed between the nozzle 7 and the nozzle 21, the head cap 14 prevents the nozzle 21 from being exposed, thereby reducing the evaporation of volatile components that cause such clogging.

  Further, when printing is started by preventing the nozzle 21 from being exposed by the head cap 14 in this way, the head cap 14 moves and is attached to the nozzle sheet surface by the cleaning roller 25 provided inside the head cap 14. Ink residue is removed. At this time, the ink remaining on the nozzles 21 is sucked out by the cleaning roller 25, and the ink remaining on the nozzles 21 is discharged. Also in this way, the ink component remaining in the nozzle 21 is discharged from the nozzle 21 by the subsequent preliminary discharge.

  However, in this type of printer 1, since the amount of ink droplets changes due to the change in the ejection direction (FIG. 14), the preliminary ejection process is not executed as in the case of driving by print data. Most of the nozzles 21 can completely discharge the ink remaining in the nozzles 21, whereas the specific nozzle 21 cannot completely discharge the remaining ink. Further, if the ink remaining completely from such a specific nozzle 21 is to be discharged, the ink consumption increases.

  For this reason, in this embodiment, the ejection direction of ink droplets is changed randomly, and ink droplets are ejected by a predetermined number of droplets to perform preliminary ejection processing. Thus, in the printer 1, even when the ink discharge amount varies at the nozzles 21, the variation in the discharge amount is averaged, thereby reducing the variation between the nozzles 21 with respect to the discharge amount of the ink droplets. Accordingly, the amount of ink consumption can be reduced, and the situation where the ink remaining at the specific nozzle 21 cannot be completely discharged can be effectively avoided. As a result, the printer 1 can prevent wasteful ink consumption and reliably prevent nozzle clogging.

(3) Advantages of the embodiment According to the above configuration, in the preliminary ejection, by randomly changing the ejection direction, wasteful ink consumption is prevented and nozzle clogging is reliably prevented. be able to.

  Further, before the preliminary ejection, at least ink residue adhering to the tip portion of the nozzle is removed by a cleaning roller which is a cleaning member, so that nozzle clogging can be reliably prevented.

  In addition, when the cleaning member is a hygroscopic member that absorbs ink remaining in the nozzles when removing the residue, the ink left by the cleaning member is discharged during preliminary ejection. Thus, the processing can be completed, and the number of preliminary ink ejections can be reduced accordingly, and nozzle clogging can be efficiently prevented.

  In the above-described embodiments, the case where the preliminary discharge is performed by executing the cleaning process at the start of printing has been described. However, the present invention is not limited to this. When performing each fixed amount of ink consumption, when defective ejection occurs, when a paper jam occurs, when turning on the power, replacing the ink cartridge, etc. Can be set.

  In the above-described embodiment, the case where cleaning and preliminary discharge are performed by the cleaning roller is described for each cleaning process. However, the present invention is not limited to this, and cleaning and preliminary discharge by the cleaning roller are individually performed. Even if these processes are performed, such as when performing preliminary ejection every time the cleaning by the cleaning roller is performed a predetermined number of times, it can be performed at various timings as necessary.

Also in the embodiment described above has dealt with the case of improving the longitudinal direction of the image quality due to a change in the discharge direction in the line printer, the present invention is not limited to this, the change in the discharge direction only correct assembly variations of the printer head It can be widely applied to the case of using the.

  In the above-described embodiment, a case has been described in which the present invention is applied to a full-line type printer head for color printing to create four nozzle arrays. However, the present invention is not limited to this, for example, monochrome printing. For example, when the present invention is applied to a full-line type printer head for producing a single nozzle array, the present invention can be widely applied to the production of nozzle arrays with various numbers.

  In the above-described embodiments, the case where the present invention is applied to a full-line type printer head has been described. However, the present invention is not limited to this. For example, the present invention is applied to a so-called serial type printer head that moves the printer head in a specific direction. The present invention can also be widely applied when applied.

  In the above-described embodiments, the case where the present invention is applied to a thermal line printer and the pressure variable element is configured by a heating element is described. However, the present invention is not limited to this, and the piezo system, the electrostatic system, etc. The present invention can be widely applied to printers in which a pressure variable element is constituted by various elements.

  In the above-described embodiments, the case where the present invention is applied to a printer head to eject ink droplets has been described. However, the present invention is not limited to this, and instead of ink droplets, the droplets are liquids of various dyes. Droplets, liquid discharge heads that are droplets for forming a protective layer, etc., microdispensers where the droplets are reagents, various measuring devices, various test devices, and various types of droplets that are agents that protect members from etching The present invention can be widely applied to pattern drawing apparatuses and the like.

The present invention applies a plurality of pressure variable elements in one liquid chamber is provided, a printer or the like method that Ru changing the direction of the droplet flying out from the nozzle by Rukoto alter the balance of driving of the plurality of pressure variable elements can do.

6 is a flowchart illustrating a processing procedure of a central processing unit of the printer according to the embodiment of the present invention. 1 is a perspective view showing a printer according to an embodiment of the present invention. It is sectional drawing which cuts and shows the printer of FIG. 2 by the AA line. FIG. 3 is a side view showing an ink cartridge applied to the printer of FIG. 2. FIG. 3 is a cross-sectional view for explaining movement of a head cap in the printer of FIG. 2. FIG. 3 is a cross-sectional view showing a head cap in the printer of FIG. 2. It is sectional drawing with which it uses for description of the cleaning roller of the head cap of FIG. It is sectional drawing with which it uses for description of the cleaning roller of FIG. FIG. 5 is an exploded perspective view for explaining the ink cartridge of FIG. 4. It is the top view and sectional drawing which show arrangement | positioning of a heat generating element. It is a connection diagram with which it uses for description of a drive of the heat generating element of FIG. It is a connection diagram which shows the drive circuit of the heat generating element of FIG. FIG. 3 is a block diagram illustrating the printer of FIG. 2. FIG. 6 is a characteristic curve diagram showing a relationship between an ink ejection direction and an ink droplet amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Printer main body, 3 ... Paper, 7 ... Conveyor belt, 11 ... Ink cartridge, 14 ... Head cap, 21 ... Nozzle, 22 ... Nozzle sheet, 25 ... Cleaning roller , 34A, 34B... Heating element, 32... Ink chamber, 41... Main control circuit, 45 .. sub control circuit, 78.

Claims (6)

Pressure variable element for changing the pressure in the liquid chamber is provided two in one liquid chamber,
By driving the two pressure variable element, the droplets of the liquid held in the liquid chamber, pops out from the nozzle toward a processing object of the droplets,
A liquid ejecting apparatus that changes the direction in which the liquid knob pops out by differentiating energy for driving the two pressure variable elements in the liquid chamber ;
After discharging the liquid remaining in the nozzle from the nozzle by the preliminary discharge process, the liquid droplets are ejected toward the processing target,
Discharging the liquid by the preliminary ejection process is a process of ejecting the liquid droplets from the nozzle by randomly changing the direction in which the liquid droplets are ejected. The liquid discharge apparatus according to claim 1, wherein before the preliminary discharge, at least a residue of the liquid adhering to a tip portion of the nozzle is removed by a cleaning member. The cleaning member is a hygroscopic member that absorbs the liquid remaining in the nozzle when removing the residue.
The liquid discharge apparatus according to claim 2, wherein The nozzles are formed side by side,
The liquid ejecting apparatus according to claim 1, wherein the plurality of pressure variable elements are first and second heat generating elements provided side by side in the arrangement direction of the nozzles. The nozzle is an opening formed in a sheet-like member;
The liquid ejecting apparatus according to claim 3, wherein the cleaning member is a roller that moves by being pressed against a portion of the sheet-like member where the nozzle is formed. Pressure variable element for changing the pressure in the liquid chamber is provided two in one liquid chamber,
By driving the two pressure variable element, the droplets of the liquid held in the liquid chamber, pops out from the nozzle toward a processing object of the droplets,
A method of driving a liquid ejecting apparatus that changes the direction in which the droplets eject by changing the energy for driving the two pressure variable elements in the liquid chamber .
After discharging the liquid remaining in the nozzle from the nozzle by the preliminary discharge process, the liquid droplets are ejected toward the processing target,
The method for driving a liquid ejection apparatus according to claim 1 , wherein the discharge of the liquid by the preliminary ejection process is a process of randomly ejecting the liquid droplets from the nozzles by randomly changing a direction in which the liquid droplets are ejected.

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