JP2015009519A - Liquid jet apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid jet apparatus that enables anchored matter to be discharged from a nozzle in maintenance processing, even in a configuration for jetting a liquid susceptible to anchorage into the nozzle.SOLUTION: Control means consecutively applies a driving pulse for flushing to a piezoelectric element at intervals at which ink jetted from a nozzle continues without interruption, in anchored matter discharge flushing processing for discharging the anchored ink Is, which is anchored to an inner wall of a nozzle 37, from the nozzle 37.

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet recording apparatus, and in particular, by applying a driving waveform included in a driving signal to the pressure generating means, the pressure generating means is driven, and the liquid in the pressure chamber communicating with the nozzle is changed. The present invention relates to a liquid ejecting apparatus that ejects liquid from a nozzle by causing pressure fluctuation.

  The liquid ejecting apparatus includes a liquid ejecting head and ejects (discharges) various liquids from the liquid ejecting head. As this liquid ejecting apparatus, for example, there are image recording apparatuses such as an ink jet printer and an ink jet plotter. Recently, various types of liquid ejecting apparatuses are utilized by utilizing the feature that a very small amount of liquid can be accurately landed on a predetermined position. It is also applied to devices. For example, a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode forming apparatus for forming an electrode such as an organic EL (Electro Luminescence) display or FED (surface emitting display), a chip for manufacturing a biochip (biochemical element) Applied to manufacturing equipment. The recording head for the image recording apparatus ejects liquid ink, and the color material ejecting head for the display manufacturing apparatus ejects solutions of R (Red), G (Green), and B (Blue) color materials. The electrode material ejecting head for the electrode forming apparatus ejects a liquid electrode material, and the bioorganic matter ejecting head for the chip manufacturing apparatus ejects a bioorganic solution.

  Here, in recent years, the above-described printer may be used for printing on a recording medium larger than a recording medium such as a printing paper used in a general household printer, for example, an outdoor advertisement. As the recording medium in this case, in consideration of weather resistance, for example, a resin film made of vinyl chloride or a polyester fiber fabric called tarpaulin coated or laminated with a synthetic resin is used. As ink used for printing / recording on these recording media, ink containing thermoplastic resin particles (hereinafter also referred to as resin ink) may be used (see, for example, Patent Document 1). Since this resin ink forms a strong resin film when solidified on a recording medium, it is excellent in scratch resistance and weather resistance as compared with water-based ink, and is suitable for printing of outdoor advertisements and the like.

  By the way, when a resin ink is jetted onto the hydrophobic recording medium such as the resin film to record an image or the like, the resin ink that has landed on the recording medium is quickly solidified and fixed on the platen. There has been proposed a configuration in which a heating means (platen heater) for heating the recording medium is provided, and by heating the recording paper by the heating means, drying and fixing of the ink landed on the recording medium is promoted.

JP 2010-221670 A

In the configuration in which the recording medium is heated by the above heating unit, there is a problem that a part of the resin ink in the recording head is solidified by transferring the heat from the heating unit to the recording head. Similarly, in a configuration in which a photocurable ink that is cured by irradiation with light such as ultraviolet rays is ejected, the ink that has landed on the recording medium is solidified by being irradiated with ultraviolet rays from an ultraviolet irradiation device serving as a curing unit. In addition, the reflected light or the like also hits the meniscus at the nozzle of the recording head, which may cause the ink to solidify on the inner wall of the nozzle.
In particular, when the ink is solidified in the vicinity of the nozzle of the recording head, the flying direction of the ink droplet ejected from the nozzle is bent in an unintended direction due to the ink fixed on the inner wall of the nozzle, and the target on the recording medium. There was a problem that the landing position was deviated from the position where it was performed. As a result, the image quality of the image recorded on the recording medium may be degraded.

  The present invention has been made in view of such circumstances, and the object of the present invention is to allow the fixed matter to be discharged from the nozzle in the maintenance process even in a configuration in which a liquid that is easily fixed in the nozzle is ejected. The object is to provide a liquid ejecting apparatus.

The liquid ejecting apparatus of the present invention has been proposed to achieve the above-described object, and includes a pressure chamber communicating with the nozzle, and a pressure generating unit that causes a pressure fluctuation in the liquid in the pressure chamber. A liquid ejecting head capable of ejecting liquid from the nozzle by the operation of the pressure generating means;
Drive waveform generating means for generating a maintenance drive waveform for ejecting liquid from the nozzle;
Control means for controlling the ejection of the liquid from the nozzle of the liquid ejection head;
A liquid ejecting apparatus comprising:
The control means causes the pressure generating means to apply the maintenance driving waveform at a continuous interval without interruption of the liquid ejected from the nozzle in a maintenance process for discharging the solidified material from the nozzle. It is characterized by.

  According to the present invention, the maintenance process is performed so that continuously ejected liquids are connected in series without interruption, so that a relatively large pressure generated during the maintenance process is not attached to the inner wall of the nozzle. It can be made to act on the solidified product. Thereby, the solidified product can be easily discharged from the nozzle. For this reason, even in a configuration that uses a liquid that is easily fixed in the nozzle, occurrence of problems such as a flying curve of the liquid due to the solidified product is reduced. As a result, it is possible to suppress deterioration in the image quality of the recorded image.

  In the above-described configuration, it is desirable to employ a configuration in which an application frequency of the maintenance drive waveform to the pressure generating unit is 40 kHz or more, and more preferably 45 kHz or more.

  According to the above configuration, when the application frequency of the maintenance drive waveform is 40 kHz or more, it is possible to continuously connect the continuously ejected liquids without interruption, and desirably 45 kHz or more. An effective flow can be generated by discharging the solidified material in the nozzle.

  In the above configuration, it is desirable to adopt a configuration in which the duration of the maintenance process is at least 50 [ms] or more.

  According to this configuration, if the duration of the maintenance process is at least 50 [ms] or more, the effect of discharging the solidified material in the nozzle by the maintenance process is likely to occur.

In addition, the present invention is suitable for a configuration having a curing unit that accelerates the curing of the liquid that has landed on the landing target.
In the above configuration, the liquid contains thermoplastic resin particles and has a viscosity at 50 ° C. of 2.1 mPa · s or more,
The recording / curing unit may employ a configuration that is a heating unit that heats the landing target.

  In the above configuration, the control unit may employ a configuration in which the maintenance process is performed when the duration of the liquid ejection process on the landing target is equal to or greater than a preset threshold value.

  According to this configuration, since the maintenance process is performed when the duration of the ejection process is equal to or greater than the threshold value, it is possible to easily and surely suppress problems such as a flying curve of liquid caused by the solidified product. Become.

In addition, it comprises a detecting means capable of detecting an ejection failure of the liquid ejected from the nozzle,
The control unit may employ a configuration in which the maintenance process is executed when an ejection failure is detected by the detection unit.

  According to this configuration, since the maintenance process is performed only when an injection failure occurs, it is possible to reduce unnecessary maintenance processes. Thereby, it becomes possible to suppress consumption of the liquid.

Further, wiping means for wiping the nozzle surface of the liquid jet head is provided,
The wiping means preferably employs a configuration in which the nozzle surface is wiped after the maintenance process is performed.

2 is a side view illustrating an internal configuration of the printer. FIG. 2 is a front view illustrating an internal configuration of the printer. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a schematic diagram explaining the principle of the inspection of the injection state by an injection inspection part. FIG. 2 is a cross-sectional view illustrating an internal configuration of a recording head. It is a schematic diagram explaining a mode that ink is ejected from a nozzle. It is a flowchart explaining the flow of the maintenance process performed during a recording process. It is a table | surface which shows the state of an ink flight curve when changing the execution space | interval of a solidified substance discharge flushing process with respect to the surface temperature of a recording medium. It is a wave form diagram explaining an example of the drive signal for flushing. It is a wave form diagram explaining an example of a structure of the drive pulse for flushing. It is a flowchart explaining the flow of the maintenance process in 2nd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet recording apparatus (hereinafter referred to as a printer) will be described as an example of the liquid ejecting apparatus of the invention.

  FIG. 1 is a side view illustrating the internal configuration of the printer 1, FIG. 2 is a front view illustrating the internal configuration of the printer 1, and FIG. 3 is a block diagram illustrating the electrical configuration of the printer 1. In FIG. 1, the platen 12 is shown in cross section. The external device 2 is an electronic device such as a computer, a digital camera, or a mobile phone. The external device 2 is electrically connected to the printer 1 wirelessly or in a wired manner. In order to print an image or text on a resin film or the like to be described later in the printer 1, print data corresponding to the image or the like is sent to the printer 1. Send.

  The printer 1 in this embodiment has a printer controller 7 and a print engine 13. A recording head 6, which is a kind of liquid ejecting head, is attached to the bottom surface side of a carriage 16 on which an ink cartridge 17 (liquid supply source) is mounted. The carriage 16 is configured to reciprocate along the guide rod 18 by the carriage moving mechanism 4. That is, the printer 1 sequentially transports the recording medium S (a kind of landing target) such as a resin film or a tarpaulin onto the platen 12 by the paper feed mechanism 3 and moves the recording head 6 in the width direction (main scanning direction) of the recording medium S. ) By ejecting ink (resin ink, which will be described later) from the nozzles 37 (see FIGS. 4 and 5 and the like) of the recording head 6 and landing the ink on the recording medium S. Record. It is also possible to adopt a configuration in which the ink cartridge 17 is disposed on the main body side of the printer, and the ink of the ink cartridge 17 is sent to the recording head 6 side through a supply tube.

  The platen 12 (a type of support member) of the printer 1 in this embodiment is divided into three parts in the conveyance direction (sub-scanning direction) of the recording medium S. Specifically, a main platen 12a disposed at a position facing the nozzle surface (surface on the ink ejection side of the nozzle plate 31) of the recording head 6 when ink is ejected onto the recording medium S, and the main platen 12a. An upstream platen 12b disposed on the upstream side (paper feeding side) in the sub-scanning direction, and a downstream platen 12c disposed on the downstream side (paper discharge side) in the sub-scanning direction with respect to the main platen 12a. It is configured. Each platen 6 is provided with a platen heater 14 as heating means (or curing means). Specifically, a main heater 14a is provided in the main platen 12a, a preheater 14b is provided in the upstream platen 12b, and an after heater (post heater) 14c is provided in the downstream platen 12c. ing. These heaters 14a to 14c are heating means or curing means for accelerating the curing and fixing of the ink landed on the recording medium S by heating the recording medium S. Each of the heaters 14a to 14c can be individually set in temperature according to the type of the recording medium S, the recording mode, and the like.

  A home position which is a standby position of the recording head 6 is set at a position deviated from one end side (right side in FIG. 2) in the main scanning direction with respect to the platen 12. In this home position, a capping mechanism 20 (capping means) and a wiping mechanism 22 (wiping means) are provided in this order from one end side. The home position is provided with a flushing box 23 as a flushing region at the other end (left side in FIG. 2) in the main scanning direction across the platen 12. The capping mechanism 20 includes, for example, a cap 25 made of an elastic member such as an elastomer, and the cap 25 is in contact with the nozzle surface (nozzle plate 31) of the recording head 6 and sealed (capping). State) or a retreat state separated from the nozzle surface. The cap 25 is formed in a tray shape having an opening on the surface that contacts the nozzle surface of the recording head 6, and is designed to have a size that can cover all nozzles on the nozzle surface. That is, when a plurality of nozzle rows (nozzle groups) composed of a plurality of nozzles are provided on the nozzle surface, all nozzle rows can be covered in a capped state.

  During standby such as when the printer 51 is turned off, the nozzle surface of the recording head 6 is capped, and the evaporation of the ink solvent from the nozzles is thereby suppressed. Although not shown, the capping mechanism 20 includes a drainage tube and a suction pump provided in the middle of the drainage tube. One end of the drainage tube is connected to the cap 25, and the other end communicates with a drainage tank (not shown). Then, the capping mechanism 20 operates the suction pump in a state where the nozzle surface is capped with the cap 25, thereby negative pressure is generated in the sealed empty portion of the cap 25. As a result, a so-called cleaning process is performed to discharge thickened ink, bubbles, and the like from the nozzles of the capped nozzle row. The capping mechanism 20 also functions as a part of an injection inspection unit 19 described later.

  The wiping mechanism 22 has a wiper 26 that can move along a direction (nozzle row direction or sub-scanning direction) intersecting the main scanning direction, and the wiper 26 with respect to the nozzle surface of the recording head 6. It can be converted into a contact state or a retracted state separated from the nozzle surface. For the wiper 26, various configurations can be adopted. For example, the blade body having elasticity has a surface covered with a cloth. The wiping mechanism 22 wipes the nozzle surface by sliding the wiper 26 from one side of the nozzle row to the other side in a state where the wiper 26 is in contact with the nozzle surface.

  The flushing box 23 has a tray-shaped ink receiving portion 27 that receives ink ejected in the flushing process for forcibly ejecting ink from the nozzles of the recording head 6 regardless of the recording process for the recording medium. The position of the ink receiving portion 27 is fixed. One end of a drain tube (not shown) is connected to the ink receiver 27 and communicates with the drain tank. In addition, a suction pump is provided in the middle of the drainage tube. By operating this suction pump, the ink in the ink receiving portion 27 is discharged to the drainage tank through the drainage tube.

  The printer controller 7 is a control unit that controls each part of the printer. The printer controller 7 in the present embodiment includes an interface (I / F) unit 8, a control unit 9, a storage unit 10, and a drive signal generation unit 11. The interface unit 8 transmits / receives printer status data when sending print data or a print command from the external device 2 to the printer 1 or outputting status information of the printer 1 to the external device 2 side. The control unit 9 is an arithmetic processing device for controlling the entire printer. The memory | storage part 10 is an element which memorize | stores the data used for the program and various control of the control part 9, and contains ROM, RAM, and NVRAM (nonvolatile memory element). The control unit 9 controls each unit according to a program stored in the storage unit 10. In addition, the control unit 9 according to the present embodiment generates ejection data indicating at which timing from which nozzle 37 the ink is ejected during the recording process based on the print data from the external device 2, and the ejection data is recorded on the recording head. 6 to the head control unit 15. Furthermore, the control part 9 in this embodiment functions as a control means for performing a solidified material discharge flushing process which is a kind of maintenance process. Details of this point will be described later.

  The drive signal generation unit 11 functions as drive waveform generation means in the present invention, and generates a drive signal including a drive pulse for recording an image or the like by ejecting ink onto the recording medium S. Further, the drive signal generator 11 in the present embodiment is configured to be able to generate a plurality of maintenance drive signals (flushing drive signals COM1, COM2) including a maintenance drive waveform (flushing drive pulse Pf). Details of the maintenance process using the maintenance drive signal will be described later.

  Next, the print engine 13 will be described. As shown in FIG. 3, the print engine 13 includes a paper feed mechanism 3, a carriage moving mechanism 4, a linear encoder 5, a platen heater 14, an ejection inspection unit 19, a recording head 6, and the like. The carriage moving mechanism 4 includes a carriage 16 to which the recording head 6 is attached and a drive motor (for example, a DC motor) that drives the carriage 16 via a timing belt or the like (not shown). The mounted recording head 6 is moved in the main scanning direction. The paper feed mechanism 3 includes a paper feed motor (not shown), paper feed rollers 3a and 3b, and the like, and sequentially feeds the recording medium S onto the platen 12 to perform sub-scanning. Further, the linear encoder 5 outputs an encoder pulse corresponding to the scanning position of the recording head 6 mounted on the carriage 16 to the printer controller 7 as position information in the main scanning direction. The printer controller 7 can grasp the scanning position (current position) of the recording head 6 based on the encoder pulse received from the linear encoder 5 side.

  FIG. 4 is a schematic diagram for explaining the principle of the injection state inspection by the injection inspection unit 19. The ejection inspection unit 19 detects the flying speed of the ink when the ink is ejected from the nozzle 37 of the recording head 6 to the cap 25 as a liquid receiving unit provided in the capping mechanism 20 at the home position. This is a mechanism for inspecting the ejection state of each nozzle 37 of the head 6. Inside the cap 25 of the capping mechanism 20, a mesh-like electrode member 29 is disposed together with the conductive ink absorber 28. For example, the electric field is applied so that the electrode member 29 is a positive electrode and the nozzle plate 31 of the recording head 6 is a negative electrode. Here, since the electrode member 29 is in contact with the conductive ink absorbing material 28, the surface of the ink absorbing material 28 has the same potential as the electrode member 29. The ejection inspecting unit 19 is configured to detect a voltage change until the ink is ejected from the nozzle 37 and land on the surface of the ink absorbing material 28 in the cap 25, and output the detected signal to the printer controller 7. ing. The maintenance process using this injection inspection unit 19 will be described later in the second embodiment.

FIG. 5 is a cross-sectional view of the main part for explaining the internal configuration of the recording head 6.
The recording head 6 in the present embodiment is schematically configured from a nozzle plate 31, a flow path substrate 32, a piezoelectric element 33, and the like, and is attached to the case 35 in a state where these members are laminated. The nozzle plate 31 is a plate-like member in which a plurality of nozzles 37 are opened in a row along the same direction at a pitch corresponding to the dot formation density. In the present embodiment, two nozzle rows (a kind of nozzle group) composed of a plurality of nozzles 37 arranged side by side are arranged side by side on the nozzle plate 31. The surface of the nozzle plate 31 on which ink is ejected corresponds to the nozzle surface.

  In the flow path substrate 32, a plurality of pressure chambers 38 partitioned by a plurality of partition walls are formed corresponding to the respective nozzles 37. A common liquid chamber 39 that partitions a part of the common liquid chamber 39 is formed outside the row of pressure chambers 38 in the flow path substrate 32. The common liquid chamber 39 communicates with each pressure chamber 38. Further, the ink from the ink cartridge 17 side is introduced into the common liquid chamber 39 through the ink introduction path 42 of the case 35. A piezoelectric element 33 (a kind of pressure generating means) is formed on the upper surface of the flow path substrate 32 opposite to the nozzle plate 31 via an elastic film 40. The piezoelectric element 33 is formed by sequentially laminating a metal lower electrode film, a piezoelectric layer made of, for example, lead zirconate titanate and the like, and an upper electrode film made of metal (both not shown). Yes. The piezoelectric element 33 is a so-called flexural mode piezoelectric element, and is formed so as to cover the upper portion of the pressure chamber 38. In the present embodiment, two piezoelectric element arrays corresponding to the two nozzle arrays are juxtaposed in a direction orthogonal to the nozzle array in a state where the piezoelectric elements 33 are staggered when viewed in the nozzle array direction. Each piezoelectric element 33 is deformed when a drive signal is applied through the wiring member 41. As a result, a pressure fluctuation occurs in the ink in the pressure chamber 38 corresponding to the piezoelectric element 33, and the ink is ejected from the nozzle 37 by controlling the pressure fluctuation of the ink.

Next, the operation of the printer 1 having the above configuration will be described.
The ink used in this embodiment is a resin ink containing thermoplastic resin particles. As this resin ink, one having a viscosity at 50 ° C. of 2.1 mPa · s or more is used. The printer 1 ejects the ink from the nozzles 37 of the recording head 6 onto a hydrophobic recording medium S such as a resin film, and performs a printing process (recording process, a kind of liquid ejection process) such as an image. At this time, the recording medium S is heated by the heater 14 provided on the platen 12. Specifically, first, the recording medium S is heated by the preheater 14b in the upstream platen 12b (preliminary heating). Thereafter, the recording medium S is sent to the main platen 12a, and the recording process is performed by ejecting ink while the recording head 6 moves relative to the recording medium S in the main scanning direction while being heated by the main heater 14a. . By heating the recording medium S, the resin ink that has landed on the recording medium S is heated to such an extent that it does not solidify, so that it is quickly fixed at the landing position (temporarily fixed). Then, when the recording medium S after recording is discharged from the printer 1, it is further heated by the after heater 14c in the downstream platen 12c, and the solvent component of the ink on the recording medium S is evaporated, and the resin is removed. Filmed and fixed (main fixing). In this way, the pigment component is fixed on the recording medium S while being covered with the resin.

  FIG. 6 is a schematic diagram for explaining how ink is ejected from the nozzles 37 of the recording head 6. FIG. 6A shows a state in which the ink droplet Id is normally ejected from the nozzle 37 during the recording process on the recording medium S. Under normal conditions, the ink droplet Id ejected from the nozzle 37 can land on the target landing position with respect to the recording medium S. However, in the configuration in which the recording medium S is heated by the heater 14 and the fixing and curing (solidification) of the resin ink is promoted as in the present embodiment, the heat from the heater 14 is transmitted to the recording head 6, thereby the recording head 6. There was a problem that a part of the resin ink solidified. In particular, as shown in FIG. 6B, when the ink is solidified inside the nozzle 37 of the recording head 6, the ink droplet Id ejected from the nozzle 37 due to the ink Is fixed to the inner wall of the nozzle 37. There is a problem that the flying direction is bent in an unintended direction and the landing position is deviated from the target dot formation position on the recording medium S. In view of such a problem, in the printer 1 according to the present invention, in the maintenance process (solidified substance discharge flushing process) periodically performed during the recording process (printing process), the solidified substance inside the nozzle 37 is fixed. It is devised to remove the ink Is. Hereinafter, this point will be described.

  FIG. 7 is a flowchart for explaining the flow of the maintenance process executed during the recording process. The solidified product discharge flushing process in the present embodiment is a maintenance process performed separately from a general flushing process performed for each pass during the recording process. Below, it demonstrates on the premise of the solidification discharge | emission flushing process. First, when the printer controller 7 receives print data from the external device 2 (step S1), the recording medium S is fed to the platen 12 and recording processing is started (step S2). As described above, the recording medium S is sequentially heated by the platen heaters 14a, 14b, and 14c. In the recording process, the control unit 9 functioning as a control unit determines whether or not the flushing timing has come (step S3). In the present embodiment, the flushing timing is determined based on the elapsed time from when the recording process is started or when the previous solidified product discharge flushing process is performed in the recording process that is being executed. A threshold is set for the elapsed time. In the present embodiment, for example, the solidified product discharge flushing process is executed every 20 minutes. The threshold value is a time that is based on the time before the occurrence of ink flying bend due to the fixed ink Is according to the surface temperature of the recording medium S (temperature estimated from the set temperature of the platen heater). Since this threshold varies depending on conditions such as the type of ink and temperature, an optimal value is determined by performing a test or the like in advance.

  FIG. 8 is a table showing the state of the flying curve of ink when the execution interval of the solidified product discharge flushing process is changed with respect to the surface temperature of the recording medium S. In the drawing, “◯” indicates that the flying curve of the ink is within the allowable range in all the nozzles 37 of the recording head 6. Similarly, “△” indicates that the number of nozzles 37 in which the flying curve of ink exceeds the allowable range is 1 or more and 10 or less, and “×” indicates that the flying curve of ink exceeds the allowable range. This indicates that the number of nozzles 37 exceeds 10. If the solidified product discharge flushing process is performed more than necessary, the ink is wasted, and it is desirable to execute the solidified product discharge flushing process at the maximum interval within the allowable range. Accordingly, when the surface temperature of the recording medium S is 50 ° C., the maximum value within the allowable range is set to 20 minutes. Similarly, when the surface temperature of the recording medium S is 45 ° C., the maximum value within the allowable range is set to 20 minutes, and when the surface temperature of the recording medium S is 40 ° C., the maximum value within the allowable range is set. If it is set to 30 minutes and the surface temperature of the recording medium S is 50 ° C., it is set to 35 minutes which is the maximum value within the allowable range. These values are examples, and change according to the glass transition point and curing characteristics of the ink.

  If it is determined in step S3 that the flushing timing has not arrived (No), the solidified product discharge flushing process is not executed, and the process proceeds to step S6. On the other hand, when it is determined in step S3 that the flushing timing has arrived (Yes), the control unit 9 controls the carriage moving mechanism 4 to move the carriage 16 onto the flushing box 23. In this state, the solidified product discharge flushing process is executed (step S4). In the solidified product discharge flushing process according to the present embodiment, the flushing drive pulse Pf (a kind of maintenance drive waveform) shown in FIG. 10 is continuously applied to the piezoelectric element 33, whereby the ink in the pressure chamber 38 is recorded. By applying a stronger pressure fluctuation, ink is forcibly ejected from the nozzle 37 to the flushing box 23.

  FIG. 9 is a waveform diagram for explaining an example of a flushing drive signal used in the solidified product discharge flushing process. FIG. 10 is a waveform diagram for explaining an example of the configuration of the flushing drive pulse Pf (a kind of maintenance drive waveform) included in the flushing drive signal COM. In the solidified product discharge flushing process according to the present embodiment, the drive signal generator 11 simultaneously generates two drive signals, a first flushing drive signal COM1 and a second flushing drive signal COM2. These flushing drive signals COM1 and COM2 are repeatedly generated at a period T (unit period) defined by the timing signal LAT generated based on the encoder pulse. In the present embodiment, the unit period T is divided into a first period T1 in the first half and a second period T2 in the second half. In the first flushing drive signal COM1, one fine vibration drive pulse Pv is generated within the first period T1, and two flushing drive pulses Pf are generated within the second period T2. The second flushing drive signal COM2 generates two flushing drive pulses Pf within the first period T1, and the potential is constant at the reference potential Vs in the second period T2. In the solidified product discharge flushing process, the drive pulses included in the drive signals COM1 and COM2 are selectively applied to the piezoelectric element 33 to perform the solidified product discharge flushing process or the fine vibration process. In the fine vibration process, a fine vibration drive pulse Pv is applied to the piezoelectric element 33 to cause a pressure fluctuation in the ink in the pressure chamber 38 to such an extent that the ink is not ejected from the nozzle 37. In this process, the ink in 37 is slightly vibrated and stirred.

  The flushing drive pulse Pf is a drive pulse that is set so that the pressure fluctuation generated in the pressure chamber 38 when the piezoelectric element 33 is driven is larger than the drive pulse for recording processing. The flushing drive pulse Pf includes the preliminary expansion part p1, the expansion hold part p2, the contraction part p3, the contraction hold part p4, the first reexpansion part p5, the intermediate hold part p6, and the second reexpansion part. It consists of p7, a re-expansion hold part p8, and a return contraction part p9. The preliminary expansion portion p1 is a waveform portion in which the potential changes from the reference potential Vs to the expansion potential VL toward the ground potential GND (minus (first potential) side). This preliminary expansion part p1 is comprised from the front side preliminary expansion part p1a and the back side preliminary expansion part p1b. The potential change rate (slope) of the front side pre-expansion part p1a is set more gently than the potential change rate of the rear side pre-expansion part p1b. The expansion hold part p2 is a waveform part that maintains the expansion potential VL that is the terminal potential of the preliminary expansion part p1 (rear side preliminary expansion part p1b) for a certain period of time. The contraction part p3 is a waveform part in which the potential changes from the expansion potential VL to the contraction potential VH beyond the reference potential Vs toward the plus (second potential) side with a relatively steep slope. The contraction hold unit p4 is a waveform unit that maintains the contraction potential VH for a predetermined time. The first reexpansion portion p5 is a waveform portion in which the potential changes to the GND side with a relatively steep gradient from the contraction potential VH to the first intermediate potential VM1 (Vs <VM1 <VH). The intermediate hold unit p6 is a waveform unit that maintains the first intermediate potential VM1 for a certain period of time. The second reexpansion part p7 is a waveform part in which the potential changes to the GND side with a relatively gentle gradient from the first intermediate potential VM1 to the reference potential Vs to the second intermediate potential VM2. The re-expansion hold unit p8 is a waveform unit that maintains the second intermediate potential VM2 for a certain period of time, and the return contraction unit p9 is a waveform unit in which the potential gradually returns from the second intermediate potential VM2 to the reference potential Vs.

  When the flushing drive pulse Pf configured as described above is applied to the piezoelectric element 33, first, the piezoelectric element 33 is deflected to the outside of the pressure chamber 38 (side away from the nozzle plate 31) by the preliminary expansion portion p1, Along with this, the pressure chamber 38 expands from the reference volume corresponding to the reference potential Vs to the expansion volume corresponding to the expansion potential VL (first changing step). By this expansion, the ink surface (meniscus) in the nozzle 37 is largely drawn toward the pressure chamber 38 side. Here, since the potential change rate of the front side pre-expansion part p1a is set more moderately than the potential change rate of the rear side pre-expansion part p1b, the initial pressure chamber 38 expands relatively moderately, It expands rapidly. Thereby, when the flushing drive pulse Pf is continuously applied to the piezoelectric element 33 and the ink is continuously ejected from the nozzle 37, the ink is prevented from being interrupted. That is, the rear end portion of the ink droplet ejected by the previous flushing drive pulse Pf is less likely to be drawn into the pressure chamber 38 side during the preliminary expansion of the pressure chamber 38 by the preliminary expansion portion p1 of the subsequent flushing drive pulse Pf. In addition, the ink droplets are prevented from being interrupted during continuous ejection. Further, since the potential change rate of the rear side pre-expansion part p1b is set steeper than the potential change rate of the front side pre-expansion part p1a, it is reduced that the time of the pre-expansion part p1 becomes redundant. The expanded state of the pressure chamber 38 is maintained for a certain period of time by the expansion hold part p2 (hold process).

  After the hold by the expansion hold part p2, the piezoelectric element 33 bends inside the pressure chamber 38 (side close to the nozzle plate 31) by the contraction part p3. Accordingly, the pressure chamber 38 is rapidly contracted from the expansion volume to the contraction volume corresponding to the reference potential Vs (second change process). As a result, the ink in the pressure chamber 38 is pressurized and an ink droplet Id is ejected from the nozzle 37. Subsequently, when the first re-expansion part p <b> 5 is applied, the piezoelectric element 33 is bent slightly toward the outside of the pressure chamber 38. Accordingly, the pressure chamber 38 expands again from the contracted volume to the intermediate volume corresponding to the first intermediate potential VM1 (third change process). Thereby, the meniscus is slightly pulled toward the pressure chamber 38 side. The pull-in at this time prevents the so-called dot omission that prevents the ink from being ejected after being dragged by the ejected ink droplet Id and destroying the meniscus, and also causes the trailing edge portion of the ink droplet Id to fly. This is to make it easier to combine with the subsequent ink droplet Id by suppressing the speed. The expansion state of the pressure chamber 38 is maintained for a predetermined time by the intermediate hold part p6 (intermediate hold process). Thereafter, the second re-expansion part p <b> 7 is applied, so that the piezoelectric element 33 is slightly bent toward the outside of the pressure chamber 38. Accordingly, the pressure chamber 38 expands again from the intermediate volume to the re-expansion volume corresponding to the second intermediate potential VM2 (fourth changing step). As a result, the meniscus is further pulled slightly toward the pressure chamber 38 side. The ink droplet Id is temporarily separated from the meniscus by this series of meniscus drawing. After the re-expansion / expansion volume is maintained for a certain period of time by the re-expansion hold part p8 (re-expansion hold process), the piezoelectric element 33 is bent toward the inside of the pressure chamber 38 by the return contraction part p9, and corresponds to the reference potential Vs. Return to the steady position. As a result, the pressure chamber 38 expands and returns from the re-expanded volume to the reference volume (returning step). At this time, the meniscus is slightly pushed out to the ejection side.

  In the solidified product discharge flushing process, two flushing drive pulses Pf of the second flushing drive signal COM2 are selected and applied to the piezoelectric element 33 in the first period T1. In the second period T2, two flushing drive pulses Pf of the first flushing drive signal COM1 are selected and applied to the piezoelectric element 33. Therefore, four flushing drive pulses Pf per unit period T are sequentially applied to the piezoelectric element 33. The application frequency (drive frequency) of the flushing drive pulse Pf to the piezoelectric element 33 is set to 40 kHz or more, more desirably 45 kHz or more. In this manner, ink is ejected continuously to all the nozzles 37 of the recording head 6. As a result, as shown in FIG. 6C, the ink droplets Id ejected from the nozzles 37 are connected in series without interruption. Then, a continuous flow is generated in the nozzle 37, so that the solidified product discharge flushing process is relatively large (compared with the pressure change during jetting in the printing process and the pressure change during jetting in the conventional general flushing process). The large pressure change also acts on the fixed ink Is attached to the inner wall of the nozzle 37. At this time, the pressure applied to the ink inside the nozzle 37 or the fixed ink Is is preferably 370 kPa or more, and preferably 400 kPa or more. By repeating such a strong pressure change, it is possible to discharge from the nozzle 37 the air bubbles that have accumulated in the ink flow path the fixed ink Is on the inner wall of the nozzle 37 together with the ink.

  By performing the solidified product discharge flushing process for at least 50 [ms] or more, the discharge effect of the fixed ink Is in the nozzle 37 is easily generated. The upper limit for continuing the solidified material discharge flushing process is until a dot dropout occurs in any of the nozzles 37 or a limit based on excessive heat generation by driving the piezoelectric element 33 occurs, but before these reductions occur. You may end. If the frequency of applying the flushing drive pulse Pf to the piezoelectric element 33 is 40 kHz or more, the continuously ejected inks can be connected in series without interruption, and 45 kHz or more. If so, an effective flow can be generated by discharging the solidified material in the nozzle 37.

  After the solidified product discharge flushing process is completed, there is a possibility that dots are missing from the nozzle 37. Therefore, by performing the cleaning process (step S5) in the capping mechanism 20, ink or bubbles are forced from the nozzle 37. Then, the meniscus of the nozzle 37 is restored to a normal state. Further, in the solidified product discharge flushing process, since a large amount of ink is discharged, there is a possibility that ink is attached to the surface of the nozzle plate 31, so that the nozzle surface is wiped by the wiper 26 of the wiping mechanism 22. Then, it is determined whether or not a series of printing processes (print job) based on the print data is completed (step S6). If it is determined that a series of printing processes is not completed (No), the process returns to step S2. The subsequent processing is repeated. On the other hand, if it is determined that a series of printing processes has been completed, the process ends.

As described above, in the printer 1 according to the present invention, the solidified product discharge flushing process is performed so that the continuously ejected ink droplets Id are continuously connected without interruption, thereby generating a continuous flow in the nozzle 37. A relatively large pressure change due to the solidified product discharge flushing process can be applied to the fixed ink Is attached to the inner wall of the nozzle 37. Thereby, the fixed ink Is can be discharged from the nozzle 37. For this reason, even in a configuration in which ink that is easily fixed in the nozzle 37 is used, occurrence of ink flying bend caused by the fixed ink Is is reduced. As a result, it is possible to suppress deterioration in the image quality of the recorded image.
In the present embodiment, the solidified material discharge flushing process is executed when the duration of the recording process is equal to or greater than the threshold value. Therefore, it is possible to easily and surely solve problems such as ink flying bend caused by the fixed ink Is. It becomes possible to suppress.

Next, a second embodiment of the present invention will be described.
FIG. 11 is a flowchart for explaining the flow of maintenance processing in the second embodiment. In the first embodiment, the configuration in which the flushing timing is determined based on the elapsed time of the recording process is illustrated. However, in the present embodiment, the ejection inspection of the nozzle 37 by the ejection inspection unit 19 is periodically performed during the recording process. Is executed, and the flashing timing is determined based on the result of the injection inspection, which is different from the first embodiment. Since other processes are generally the same as those in the first embodiment, the differences will be mainly described below.
After the recording process is started, the recording process is interrupted every certain time or every predetermined number of passes, and the injection inspection process is executed (step S3a). That is, the controller 9 moves the carriage 16 to the capping mechanism 20 at the home position, and in this state, ejects ink from each nozzle 37 toward the cap 25 of the capping mechanism 20 to execute the ejection inspection process. . When the ejection direction of the ink ejected from the nozzle 37 is significantly bent or an ejection abnormality such as the ink not ejecting from the nozzle 37 occurs, the value of the detection signal from the ejection inspection unit 19 is normal. It changes from the value of. The controller 9 determines whether or not there is an ejection abnormality in the nozzle 37 based on the change in the detection signal (step S3b). If it is determined in step S4 that no injection abnormality has occurred (No), the solidified product discharge flushing process is not executed, and the process proceeds to step S6. On the other hand, if it is determined in step S <b> 3 b that an injection abnormality has occurred (Yes), the control unit 9 controls the carriage moving mechanism 4 to move the carriage 16 onto the flushing box 23. Then, in this state, the same solidified product discharge flushing process as that of the first embodiment is executed (step S5).
According to the present embodiment, since the solidified product discharge flushing process is performed when an ejection abnormality occurs in the nozzle 37, the wasteful execution of the solidified product discharge flushing process is reduced. For this reason, it is possible to suppress ink consumption.

In the above-described embodiment, the so-called flexural vibration type piezoelectric element 23 is exemplified as the pressure generating unit. However, the pressure generation unit is not limited thereto, and for example, a so-called longitudinal vibration type piezoelectric element can be employed. In this case, the drive pulse Pf (or Pv) illustrated in the above embodiment has a waveform in which the direction of potential change, that is, the top and bottom are inverted.
In addition, the pressure generating means is not limited to the piezoelectric element, and various pressure generating means such as a heat generating element that generates bubbles in the pressure chamber and an electrostatic actuator that changes the volume of the pressure chamber using electrostatic force are used. The present invention can also be applied.

  Further, in each of the above-described embodiments, the configuration in which the resin ink containing the thermoplastic resin particles is ejected is exemplified. However, the present invention is not limited to this. For example, the photocurable ink that is cured by irradiating light such as ultraviolet rays is ejected. The present invention is also suitable for such a configuration. That is, in the case of using a photocurable ink, a configuration is adopted in which the ink that has landed on the recording medium S is irradiated with ultraviolet rays from an ultraviolet irradiation device serving as a curing unit to promote curing and fixing of the ink. In this case, the reflected light or the like also hits the meniscus in the nozzles of the recording head, which may cause the ink to solidify on the nozzle inner wall. Therefore, by adopting the present invention even in such a configuration, it is possible to suppress problems such as flying bending due to the fixed ink.

  Moreover, in the said embodiment, although the platen heater 14 was illustrated as a heating means, it is not restricted to this. As long as the ink on the recording medium S can be heated, the present invention can be applied to a configuration in which the ink is heated from above the recording medium S on the platen 12 using an infrared heater, for example.

  Furthermore, in the said embodiment, although the ejection test | inspection part 19 was illustrated using the voltage change when an ink ejects between the nozzle member 31 which functions as an electrode, and the electrode member 29 of the cap 25 as a detection means, This is not a limitation. For example, other detection means such as a configuration for optically inspecting the ejection state of ink from the nozzles and a configuration for detecting the ejection state of ink based on the residual vibration of the piezoelectric element 33 may be employed.

  The present invention is not limited to the above printer as long as it is a liquid ejecting apparatus that ejects a liquid that is easily fixed in the nozzle, and various ink jet recording apparatuses such as a plotter, a facsimile machine, and a copying machine, or a landing target. The present invention can also be applied to a printing apparatus that performs printing by landing ink from a liquid ejecting head on a fabric (printing material) that is a kind of the above.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 6 ... Recording head, 7 ... Printer controller, 9 ... Control part, 11 ... Drive signal generation part, 12 ... Platen, 14 ... Platen heater, 16 ... Carriage, 19 ... Injection inspection part, 20 ... Capping mechanism, DESCRIPTION OF SYMBOLS 22 ... Wiping mechanism, 23 ... Flushing box, 25 ... Cap, 26 ... Wiper, 27 ... Ink receiving part, 28 ... Ink absorber, 29 ... Electrode member, 31 ... Nozzle plate, 33 ... Piezoelectric element, 37 ... Nozzle, 38 ... pressure chamber

Claims (8)

A pressure chamber that communicates with the nozzle, and a pressure generating unit that generates a pressure fluctuation in the liquid in the pressure chamber, and a liquid ejecting head capable of ejecting the liquid from the nozzle by the operation of the pressure generating unit;
Drive waveform generating means for generating a maintenance drive waveform for ejecting liquid from the nozzle;
Control means for controlling the ejection of the liquid from the nozzle of the liquid ejection head;
A liquid ejecting apparatus comprising:
The control means causes the pressure generating means to apply the maintenance driving waveform at a continuous interval without interruption of the liquid ejected from the nozzle in a maintenance process for discharging the solidified material from the nozzle. A liquid ejecting apparatus.   2. The liquid ejecting apparatus according to claim 1, wherein an application frequency of the maintenance drive waveform to the pressure generating unit is 40 kHz or more, and more desirably 45 kHz or more.   The liquid ejecting apparatus according to claim 1, wherein the maintenance process has a duration of at least 50 [ms] or more.   The liquid ejecting apparatus according to claim 1, further comprising a curing unit that accelerates curing of the liquid that has landed on the landing target. The liquid is a liquid containing thermoplastic resin particles and having a viscosity at 50 ° C. of 2.1 mPa · s or more,
The liquid ejecting apparatus according to claim 4, wherein the curing unit is a heating unit that heats the landing target.   The liquid ejecting apparatus according to claim 6, wherein the control unit causes the maintenance process to be executed when a duration of the liquid ejecting process on the landing target is equal to or longer than a preset threshold value. Comprising a detecting means capable of detecting an ejection failure of the liquid ejected from the nozzle;
The liquid ejecting apparatus according to claim 1, wherein the control unit causes the maintenance process to be executed when an ejection failure is detected by the detection unit. Wiping means for wiping the nozzle surface of the liquid jet head,
The liquid ejecting apparatus according to claim 1, wherein the wiping unit performs wiping of the nozzle surface after the maintenance process is performed.

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