JP2017043036A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device capable of satisfying both of improvement of intermittent capability and securement of discharge stability.SOLUTION: A drive pulse generating circuit can generate a first vibration driving pulse causing polarities of a potential change from a reference potential to alternately differ and potential to vary three times in total and to return to the reference potential and a second vibration driving pulse causing the polarities of the potential change from the reference potential to alternately differ and the potential to vary four times in total and to return to the reference potential. When elapsed time in a non-discharge state in which liquid is not discharged after discharge treatment is started or the liquid is discharged previous time in the discharge treatment is equal to a preset threshold value or less, a liquid discharge device selects the first vibration driving pulse and applies it to an actuator corresponding to a nozzle. On the other hand, when the elapsed time exceeds the threshold value, the liquid discharge device selects the second vibration driving pulse, applies it to the actuator corresponding to the nozzle, and performs micro-vibration operation.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet recording apparatus, and more particularly to a liquid ejecting apparatus that performs a fine vibration operation that vibrates a liquid in a nozzle and a pressure chamber to such an extent that the liquid is not ejected.

  The liquid discharge apparatus includes a liquid discharge head, and discharges (sprays) various liquids from the liquid discharge head. As this liquid ejection device, for example, there are image recording devices such as an ink jet printer and an ink jet plotter, but recently, various kinds of manufacturing have been made 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 ejection head for the display manufacturing apparatus ejects a solution of each color material of R (Red), G (Green), and B (Blue). The electrode material discharge head for the electrode forming apparatus discharges a liquid electrode material, and the bioorganic discharge head for the chip manufacturing apparatus discharges a bioorganic solution.

  Here, in the above liquid discharge apparatus, while the liquid discharge process is being performed by the liquid discharge head, the nozzles of the liquid discharge head are released from the sealed state (capping state) by the sealing member such as a cap. Exposed to the air. For this reason, with the passage of time, the solvent evaporates through the surface (meniscus) of the ink exposed to the nozzle, and the liquid in the nozzle gradually thickens. When the viscosity of the liquid increases, there may be a discharge failure such that the liquid is not discharged from the nozzle or the flight direction of the liquid discharged from the nozzle is bent. In general liquid ejection devices, in order to avoid such ejection failure due to thickening of liquid such as ink, so-called flushing operation for forcibly ejecting liquid from the nozzle, cleaning operation for sucking liquid from the nozzle, etc. It was necessary to perform recovery operations periodically. However, if such a recovery operation is frequently executed, the liquid is wasted.

  Here, the ability to continue the liquid discharge process without any trouble without performing the recovery operation is referred to as intermittent ability. In other words, from the time when the discharge process as a series or batch of jobs based on the execution command from the user is started (when the nozzle surface of the liquid discharge head is released from the sealed state by the cap), or It can be said that the intermittent capability is higher as the time from the last (previous) execution of the recovery operation in the series of discharge processing to the time when the discharge processing is continued without performing the recovery operation and the discharge failure occurs is longer. In order to improve such intermittent capability, in this type of liquid ejection apparatus, for the nozzle that does not eject liquid during ejection processing (for example, during a printing operation in a printer), the nozzle is not ejected to the extent that liquid is not ejected from the nozzle. A fine vibration operation for vibrating the liquid in the inside and the pressure chamber is performed. That is, by this fine vibration operation, the liquid in the vicinity of the nozzle is agitated to suppress the progress of thickening (see, for example, Patent Document 1).

JP 2012-96423 A

  From the viewpoint of improving the intermittent capability, it is conceivable to make the micro-vibration operation stronger. Specifically, by increasing the voltage of the drive pulse applied to the actuator during the fine vibration operation, or increasing the number of drive pulses applied to the actuator per unit time, The operation can be made more powerful. However, when the fine vibration operation is made stronger, the meniscus vibration in the nozzle increases correspondingly, and the residual vibration may adversely affect the discharge stability in the subsequent discharge operation. Specifically, there is a possibility that a variation in the amount of droplets discharged from the nozzle, a flying curve, or the like may occur.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid ejection apparatus capable of achieving both improvement in intermittent capability and securing of ejection stability.

[Means 1]
The liquid discharge apparatus of the present invention has been proposed to achieve the above object, and generates a pressure vibration in a nozzle from which the liquid is discharged, a pressure chamber communicating with the nozzle, and the liquid in the pressure chamber. A liquid ejection head having an actuator and ejecting liquid from the nozzle by driving the actuator;
A drive pulse generation circuit that drives the actuator to generate a vibration drive pulse that vibrates the liquid in the pressure chamber and the nozzle;
The drive pulse generation circuit alternately changes the polarity of the potential change from the reference potential and the first vibration drive pulse in which the potential is changed three times in total and returns to the reference potential. And a second vibration drive pulse that changes the potential a total of four times and returns to the reference potential.
When the elapsed time in the non-ejection state in which no liquid is ejected after the ejection process is started or after the previous ejection of liquid in the ejection process is less than or equal to a predetermined threshold, While one vibration drive pulse is selected and applied to the actuator corresponding to the nozzle, if the elapsed time exceeds the threshold, the second vibration drive pulse is selected and applied to the actuator corresponding to the nozzle. And performing a slight vibration operation.

  According to the present invention, either the first vibration drive pulse or the second vibration drive pulse is selectively applied to the actuator in accordance with the elapsed time in the non-ejection state in the ejection process, so that more and more can be achieved. Appropriate micro-vibration is performed. As a result, it is possible to improve both the intermittent capability and ensure the ejection stability after the fine vibration operation. Since the intermittent capability is improved, the frequency of executing the recovery process such as the flushing operation and the cleaning operation can be reduced, so that the liquid consumption can be suppressed accordingly.

[Means 2]
In the configuration of the means 1, the drive pulse generating circuit can generate a third vibration drive pulse that changes the potential of the potential alternately from the reference potential and changes the potential twice in total to return to the reference potential. Yes,
If the elapsed time is less than or equal to the first threshold, the third vibration drive pulse is selected and applied to the actuator corresponding to the nozzle,
When the elapsed time exceeds the first threshold and is equal to or less than a second threshold that is longer than the first threshold, the first vibration drive pulse is selected and applied to the actuator corresponding to the nozzle. When the elapsed time exceeds the second threshold, it is preferable to adopt a configuration in which the second vibration drive pulse is selected and applied to the actuator corresponding to the nozzle.

  According to the configuration of the means 2, the fine vibration operation in which one of the first vibration drive pulse, the second vibration drive pulse, and the third vibration drive pulse is selected based on the two threshold values for the elapsed time is performed. As a result, the micro-vibration operation is executed without excess or deficiency.

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. FIG. 2 is a cross-sectional view illustrating an internal configuration of a recording head. It is a wave form diagram of the drive signal for fine vibration operation. It is a wave form diagram which shows the example of a 1st minute vibration pulse (3rd vibration drive pulse). It is a wave form diagram which shows the example of a 2nd fine vibration pulse (1st vibration drive pulse). It is a wave form diagram which shows the example of a 3rd micro vibration pulse (2nd vibration drive pulse). It is the table | surface which showed the selection example of the vibration drive pulse with respect to idle time, and the effect of the intermittent capability in that case, and discharge stability. It is a flowchart explaining the flow of the selection process of a vibration drive pulse.

  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 ejection apparatus of the present invention.

  FIG. 1 is a front view illustrating the internal configuration of the printer 1, and FIG. 2 is a block diagram illustrating the electrical configuration of the printer 1. 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 to instruct / instruct recording (ejection processing) of an image or text on a recording medium (liquid landing target) such as recording paper. Print data corresponding to the image and the like is transmitted to the printer 1 together with the instruction / command.

  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 ejection head, is attached to the bottom surface side of a carriage 16 on which an ink cartridge (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 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 6 while the nozzle 37 ( An image or the like is recorded by ejecting ink which is a kind of liquid in the present invention and landing on a recording medium. 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.

  A home position that 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 and a wiping mechanism 22 are provided in order from one end side. The capping mechanism 20 has, for example, a cap 21 made of an elastic member such as an elastomer, and the cap 21 is in contact with the nozzle surface (nozzle plate 25) of the recording head 6 and sealed (capping). State) or a retreat state separated from the nozzle surface. The capping mechanism 20 capping the nozzle surface of the recording head 6 in a standby state where the recording head 6 is not performing a recording operation on the recording medium on the platen 12, or in a state where the printer 1 is turned off. And

  The wiping mechanism 22 has a wiper 23 that can move along a direction (nozzle row direction or sub-scanning direction) intersecting the main scanning direction, and the wiper 23 is moved 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. The wiper 23 can employ various configurations. For example, the wiper 23 is formed by covering the surface of an elastic blade body with a cloth. The wiping mechanism 22 wipes the nozzle surface by sliding the wiper 23 from one side of the nozzle row to the other side with the wiper 23 in contact with the nozzle surface.

  The printer controller 7 is a control unit that controls each unit in the printer 1. The printer controller 7 in the present embodiment includes an interface (I / F) unit 8, a main control circuit 9, a storage unit 10, and a drive signal generation circuit 11 (corresponding to the drive pulse generation circuit in the present invention). . The interface unit 8 receives print data and a print command from the external device 2 to the printer 1 and outputs status information of the printer 1 to the external device 2 side. The storage unit 10 is an element that stores a program for the main control circuit 9 and data used for various controls, and includes a ROM, a RAM, and an NVRAM (nonvolatile storage element).

  The main control circuit 9 controls each unit according to a program stored in the storage unit 10. In addition, the main control circuit 9 in the present embodiment generates discharge data indicating at which timing from which nozzle 37 the ink is discharged based on the print data from the external device 2, and records the discharge data. It transmits to the head controller 15 of the head 6. Further, the timing pulse PTS is generated from the encoder pulse output from the linear encoder 5 (see FIG. 4). The main control circuit 9 controls transfer of print data, generation of a drive signal by the drive signal generation circuit 11 and the like in synchronization with the timing pulse PTS. Further, the main control circuit 9 generates a timing signal such as a latch signal LAT based on the timing pulse PTS and outputs it to the head controller 15 of the recording head 2. Further, the main control circuit 9 starts from the time when the recording operation is started based on the print command (the time when the nozzle surface of the recording head 6 is released from the capping state) or in a series of recording operations based on the print command. The elapsed time (hereinafter referred to as idle time) in the non-ejection state where ink is not ejected thereafter (however, the minute vibration operation is performed as will be described later) from the last ejection time is referred to for each nozzle 37. It also functions as a timekeeping means for keeping time. That is, at the same time as the recording operation is started, the idle running time is started for each nozzle 37 and reset (returned to the initial value) each time ink is ejected from the nozzle 37 (including ejection in the flushing operation). However, it is timed until a series of recording operations are completed.

  The head controller 15 selectively applies a drive signal to the piezoelectric element 23 based on the ejection data and the timing signal. As a result, the piezoelectric element 23 is driven, and ink droplets are ejected from the nozzles 37, or a minute vibration operation is performed to the extent that ink droplets are not ejected.

  The drive signal generation circuit 11 generates a drive signal including a drive pulse for recording an image or the like by ejecting ink onto the recording medium. In addition, the drive signal generation circuit 11 in the present embodiment generates a drive signal COMvb including a plurality of vibration drive waveforms (fine vibration pulses Pv1 to Pv3). Details of the fine vibration operation using the vibration drive waveform will be described later.

  Next, the print engine 13 will be described. As shown in FIG. 2, the print engine 13 includes a paper feeding mechanism 3, a carriage moving mechanism 4, a linear encoder 5, 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, a paper feed roller, and the like (both not shown), and sequentially feeds the recording medium 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 main control circuit 9 of 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. 3 is a cross-sectional view of the main part showing the internal configuration of the recording head 6. For convenience, the stacking direction of each member will be described as the vertical direction. In the recording head 6 in this embodiment, the nozzle plate 25, the communication substrate 26, and the pressure chamber forming substrate 27 are stacked in this order and joined together by an adhesive to form a unit. An elastic film 28, a piezoelectric element 29 (a kind of actuator), and a protective substrate 30 are laminated on the surface of the unit opposite to the communication substrate 26 side of the pressure chamber forming substrate 27 to form a piezoelectric device 31. ing. The piezoelectric device 31 is attached to the case 32 to constitute the recording head 6.

  The case 32 is a box-shaped member made of synthetic resin to which the piezoelectric device 31 is fixed on the bottom side. On the lower surface side of the case 32, an accommodation cavity 33 is formed that is recessed in a rectangular parallelepiped shape from the lower surface to the middle of the height direction of the case 32. When the piezoelectric device 31 is joined to the lower surface, the piezoelectric device 31 is formed. The pressure chamber forming substrate 27, the elastic film 28, the piezoelectric element 29, and the protective substrate 30 are accommodated in the accommodating space 33. In addition, an ink introduction path 34 is formed in the case 32. The ink from the ink cartridge 17 side is introduced into a common liquid chamber 35 described later through an ink introduction path 34.

  The pressure chamber forming substrate 27 in the present embodiment is manufactured from a silicon single crystal substrate (hereinafter also simply referred to as a silicon substrate). In the pressure chamber forming substrate 27, a plurality of pressure chamber empty portions that define the pressure chamber 38 are formed by anisotropic etching corresponding to the nozzles 37 of the nozzle plate 25. One (upper surface side) opening of the pressure chamber vacant portion in the pressure chamber forming substrate 27 is sealed by the elastic film 28. A communication substrate 26 is bonded to the surface of the pressure chamber forming substrate 27 opposite to the elastic film 28, and the other opening of the pressure chamber space is sealed by the communication substrate 26. Thereby, the pressure chamber 38 is partitioned. Here, the portion where the upper opening of the pressure chamber 38 is sealed by the elastic film 28 is a flexible surface that is displaced by driving the piezoelectric element 29. It is also possible to adopt a configuration in which the pressure chamber forming substrate 27 and the flexible surface are integrated. That is, an etching process is performed from the lower surface side of the pressure chamber forming substrate 27, and a pressure chamber cavity is formed on the upper surface side, leaving a thin portion having a thin plate thickness, and this thin portion functions as a flexible surface. It can also be adopted.

  The pressure chamber 38 in the present embodiment is a hollow portion that is long in a direction orthogonal to the direction in which the nozzles 37 are arranged side by side. One end portion of the pressure chamber 38 in the second direction communicates with the nozzle 37 via the nozzle communication port 36 (a kind of space in the present invention) of the communication substrate 26. The other end of the pressure chamber 38 in the second direction communicates with the common liquid chamber 35 (a type of space in the present invention) via the individual communication port 39 (a type of space in the present invention) of the communication substrate 26. . A plurality of pressure chambers 38 are arranged in parallel along the nozzle row direction corresponding to each nozzle 37.

  The communication substrate 26 is a plate material made of a silicon substrate in the same manner as the pressure chamber forming substrate 27. In this communication substrate 26, an empty portion serving as a common liquid chamber 35 (also called a reservoir or a manifold) provided in common to the plurality of pressure chambers 38 of the pressure chamber forming substrate 27 is formed by anisotropic etching. The common liquid chamber 35 is a long space along the direction in which the pressure chambers 38 are arranged side by side. In the present embodiment, the common liquid chamber 35 includes a first liquid chamber 35 a penetrating through the thickness direction of the communication substrate 26, and halfway in the thickness direction of the communication substrate 26 from the lower surface side to the upper surface side of the communication substrate 26. And a second liquid chamber 35b formed with a thin portion left on the upper surface side. One end (the end far from the nozzle 37) in the second direction of the second liquid chamber 35b communicates with the first liquid chamber 35a, while the other end in the same direction is below the pressure chamber 38. It is formed in the corresponding position. At the other end of the second liquid chamber 35 b, that is, at the edge opposite to the first liquid chamber 35 a, an individual communication port 39 that penetrates the thin portion is provided in each pressure chamber 38 of the pressure chamber forming substrate 27. Are formed along the nozzle row direction. The lower end of the individual communication port 39 communicates with the second liquid chamber 35 b, and the upper end of the individual communication port 39 communicates with the pressure chamber 38.

  The nozzle plate 25 is a plate material in which a plurality of nozzles 37 are opened in a row. In the present embodiment, a plurality of nozzles 37 are arranged at a pitch corresponding to the dot formation density to form a nozzle row. The nozzle plate 25 in the present embodiment is made of a silicon substrate, and a cylindrical nozzle 37 is formed on the substrate by dry etching. In the piezoelectric device 31 in this embodiment, an ink flow path is formed from the common liquid chamber 35 to the nozzle 37 through the individual communication port 39, the pressure chamber 38, and the nozzle communication port 36. .

  The elastic film 28 formed on the upper surface of the pressure chamber forming substrate 27 is made of, for example, silicon dioxide having a thickness of about 1 μm. An insulating film (not shown) is formed on the elastic film 28. This insulating film is made of, for example, zirconium oxide. And the piezoelectric element 29 is formed in the position corresponding to each pressure chamber 38 on this elastic film 28 and an insulating film, respectively. On the piezoelectric element 29, the elastic film 28 and the insulating film in the present embodiment, a metal lower electrode film, a piezoelectric layer made of lead zirconate titanate (PZT), etc., and a metal upper electrode film (all (Not shown) are sequentially stacked. In this configuration, one of the upper electrode film and the lower electrode film is a common electrode, and the other is an individual electrode. In addition, an electrode film and a piezoelectric layer serving as individual electrodes are patterned for each pressure chamber 38. In this piezoelectric element 29, a region where the piezoelectric layer is sandwiched between the upper electrode film and the lower electrode film is a piezoelectric active portion in which piezoelectric distortion occurs due to application of voltage to both electrodes. Then, the piezoelectric active portion bends and deforms according to the change of the applied voltage, so that the flexible surface that divides one surface of the pressure chamber 38, that is, the elastic film 28 approaches the nozzle 37 or moves away from the nozzle 37. Displace. As a result, pressure vibration is generated in the ink in the pressure chamber 38, and ink is ejected from the nozzles 37 using this pressure vibration.

  Next, the fine vibration operation executed during the recording operation in the printer 1 will be described.

  FIG. 4 is a waveform diagram for explaining an example of the drive signal generated by the drive signal generation circuit 11 and shows the drive signal COMvb used for the fine vibration operation. A unit period T that is a repetition period of the drive signal COMvb is the same as the unit period T of the drive signal used for ink ejection, and is defined by the latch signal LAT generated based on the timing signal PTS. This drive signal COMvb performs a fine vibration operation for the nozzles 37 (non-ejection nozzles) that do not eject ink at a predetermined cycle while the recording head 6 performs the recording operation (ink ejection process) on the recording medium S. This is a drive signal for execution. The fine vibration operation is an operation for causing pressure vibration in the ink in the pressure chamber 38 to the extent that ink is not ejected from the nozzle 37 for the purpose of stirring the ink in the nozzle 37 or the pressure chamber 38. Note that the ejection processing means processing as a single (overall) job for recording an image or the like by ejecting ink from a predetermined nozzle to the recording medium as the entire recording head 6. The ejection operation means an operation when ink is actually ejected at a predetermined cycle in the predetermined nozzle 37, and is used as a concept narrower than the ejection process.

  In the present embodiment, the unit period T is divided into a total of three pulse generation periods t1 to t3. In the first pulse generation period t1, the first pulse part P1, the second pulse generation period t2, the second pulse part P2, and the third pulse generation period t3 are generated. Then, the head controller 15 selects any one or a plurality of pulse parts in the drive signal COMvb based on the switching signals CH <b> 1 to CH <b> 3 and applies them to the piezoelectric element 29. By selectively applying a part of each pulse part P1 to P3 or a combination thereof to the piezoelectric element 29, the strength and effect of the micro-vibration operation are changed. The first pulse part P1 generated at the generation period t1 also functions as the first micro-vibration pulse Pv1 alone. Moreover, the combination of the 1st pulse part P1 and the 2nd pulse part P2 functions as the 2nd fine vibration pulse Pv2. The combination of the first pulse part P1, the second pulse part P2, and the third pulse part P3 functions as the third micro-vibration pulse Pv3. Details of these fine vibration pulses will be described later. The second pulse part P2 and the third pulse part P3 are not applied to the piezoelectric element 29 alone.

  First, each waveform element which comprises each pulse part P1-P3 is demonstrated. Each potential gradient (potential change rate per unit time) of the first expansion element p1, the first contraction element p3, the second expansion element p5, and the second contraction element p7 is applied to the piezoelectric element 29. When set, the values are set such that no ink is ejected from the nozzles 37. The first expansion element p1 has an expansion potential E1 on the negative polarity (first polarity) side of the reference potential Eb from the reference potential Eb corresponding to the reference volume of the pressure chamber 38 (volume serving as a reference for expansion or contraction). The potential is lowered at a predetermined gradient to (first potential). The first hold element p2 maintains the first expansion potential E1, which is the terminal potential of the first expansion element p1, for a certain period of time.

  The first contraction element p3 is a waveform element generated following the first hold element p2, and exceeds the reference potential Eb from the first expansion potential E1 and has a positive polarity (second second). The potential is increased at a constant gradient to the contraction potential E2 (second potential) on the polarity side. The first contraction element p3 is divided into a front contraction element p3a on the negative electrode side and a rear contraction element p3b on the positive electrode side with respect to the reference potential Eb. The pre-stage contraction element p3a is generated in the first pulse generation cycle t1, and is one element of the first pulse part P1 (first fine vibration pulse Pv1). On the other hand, the post-stage contraction element p3b is generated in the second pulse generation cycle t2 and is an element of the second pulse part P2.

  The second hold element p4 maintains the contraction potential E2 that is the terminal potential of the first contraction element p3 for a certain period of time. The second expansion element p5 is a waveform element in which the potential changes with a predetermined gradient from the contraction potential E2 to the first expansion potential E1 on the negative polarity side. Like the first contraction element p3, the second expansion element p5 is divided into a pre-stage expansion element p5a on the positive electrode side with respect to the reference potential Eb and a post-stage expansion element p5b on the negative electrode side with respect to the reference potential Eb. Is done. The pre-stage expansion element p5a is generated in the second pulse generation period t2 and is an element of the second pulse part P2. On the other hand, the post-stage expansion element p5b is generated at the third pulse generation period t3 and is an element of the third pulse part P3. The third hold element p6 is a waveform element that maintains the first expansion potential E1 for a certain period of time. The second contraction element p7 is a waveform element in which the potential returns with a constant gradient from the first expansion potential E1 to the reference potential Eb.

  FIG. 5 is a waveform diagram of the first micro-vibration pulse Pv1. The first fine vibration pulse Pv1 composed of the first pulse part P1 is a drive pulse having the weakest effect of the fine vibration operation, that is, the ink stirring effect among the fine vibration pulses, and the fine vibration operation in the liquid ejecting apparatus. This is a micro-vibration pulse generally used for the purpose. The first micro-vibration pulse Pv1 includes a first expansion element p1, a first hold element p2, and a pre-stage contraction element p3a of the first contraction element p3. The first micro-vibration pulse Pv1 having such a configuration is a drive pulse (third vibration drive according to the present invention) in which the potential changes alternately from the reference potential Eb and the potential changes twice in total to return to the reference potential Eb. Equivalent to a pulse). The pre-stage contraction element p3a is a waveform element that increases the potential from the expansion potential E1 to the reference potential Eb. When the first micro-vibration pulse Pv1 is applied to the piezoelectric element 29, first, the piezoelectric element 29 is moved from the initial position corresponding to the reference potential Eb to the outside of the pressure chamber 38 (the side away from the nozzle plate 25) by the first expansion element p1. ) And the pressure chamber 38 expands from the reference volume corresponding to the reference potential Eb to the expansion volume corresponding to the first expansion potential E1. The expansion state of the pressure chamber 38 is maintained over the application period of the first hold element p2. Subsequently, the piezoelectric element 29 is deflected to the inside of the pressure chamber 38 (side approaching the nozzle plate 25) by the pre-stage contraction element p3a, and the pressure chamber 38 returns from the expansion volume corresponding to the first expansion potential E1 to the reference volume. As described above, the expansion of the pressure chamber 38 by the first expansion element p1 and the contraction of the pressure chamber 38 by the front-stage contraction element p3a cause pressure vibration in the ink in the pressure chamber 38. And the ink in the nozzle 37 is stirred.

  In such a micro-vibration operation by the first micro-vibration pulse Pv1, the ink stirring effect is the weakest among those by each micro-vibration pulse, but the ink is not stirred more than necessary. Can be suppressed. The first micro-vibration pulse Pv1 has the shortest pulse length (time from the start to the end) of each micro-vibration pulse and the longest time from the end of the pulse to the next cycle. Can be more reliably converged. For this reason, the discharge operation after the fine vibration operation by the first fine vibration pulse Pv1 can be most stabilized. That is, when ink is ejected in the next cycle after the fine vibration operation, the amount of ink ejected from the nozzle 37 and the flying speed may vary due to residual vibration after the fine vibration operation. Suppressed reliably.

  FIG. 6 is a waveform diagram of the second micro-vibration pulse Pv2. The second micro-vibration pulse Pv2 composed of a combination of the first pulse part P1 and the second pulse part P2 is a drive pulse in which the ink stirring effect in the micro-vibration operation is enhanced as compared with the case of the first micro-vibration pulse Pv1. The second slight vibration pulse Pv2 includes a first expansion element p1, a first hold element p2, a first contraction element p3, a second hold element p4, and a pre-stage expansion element p5a. The second micro-vibration pulse Pv2 in this embodiment is a drive pulse (first vibration drive pulse in the present invention) in which the potential changes alternately from the reference potential Eb and the potential changes three times in total to return to the reference potential Eb. Equivalent). The pre-stage expansion element p5a is a waveform element that lowers the potential from the contraction potential E2 to the reference potential Eb. When the second fine vibration pulse Pv2 is applied to the piezoelectric element 29, first, the piezoelectric element 29 is bent from the initial position to the outside of the pressure chamber 38 by the first expansion element p1, and the pressure chamber 38 corresponds to the reference potential Eb. Expansion from the reference volume to the expansion volume corresponding to the first expansion potential E1. The expansion state of the pressure chamber 38 is maintained over the application period of the first hold element p2. Subsequently, the piezoelectric element 29 is bent inward of the pressure chamber 38 by the first contraction element p3, and the pressure chamber 38 rapidly contracts from the expansion volume corresponding to the first expansion potential E1 to the contraction volume corresponding to the contraction potential E2. To do. Due to the rapid contraction of the pressure chamber 38, the ink in the pressure chamber 38 is pressurized and pressure vibration is generated, whereby the ink in the pressure chamber 38 and the nozzle 37 is agitated. The expansion state of the pressure chamber 38 is maintained over the application period of the second hold element p4, and then the piezoelectric element 29 is returned to the initial position by the pre-stage expansion element p5a, and the volume of the pressure chamber 38 is returned to the reference volume. To do.

  By performing the micro-vibration operation by the second micro-vibration pulse Pv2, the volume of the pressure chamber 38 can be changed more greatly by the first contraction element p3, and the micro-vibration by the first micro-vibration pulse Pv1. The ink stirring effect is improved over the operation. Further, the pressure vibration generated by the first contraction element p3 is damped by the upstream expansion element p5a as will be described later.

  FIG. 7 is a waveform diagram of the third micro-vibration pulse Pv3. A third micro-vibration pulse Pv3 composed of a combination of the first pulse part P1, the second pulse part P2, and the third pulse part P3 includes a first expansion element p1, a first hold element p2, and a first contraction. It consists of an element p3, a second hold element p4, a second expansion element p5, a third hold element p6, and a second contraction element p7. The third micro-vibration pulse Pv3 in the present embodiment is a drive pulse (corresponding to the second vibration drive pulse in the present invention) in which the potential changes a total of four times by alternately changing the polarity of the potential change with respect to the reference potential Eb. is there.

  When the third micro-vibration pulse Pv3 configured as described above is applied to the piezoelectric element 29, first, the piezoelectric element 29 is moved from the initial position corresponding to the reference potential Eb to the outside of the pressure chamber 38 by the first expansion element p1. The pressure chamber 38 expands from the reference volume corresponding to the reference potential Eb to the expansion volume corresponding to the first expansion potential E1. The expansion state of the pressure chamber 38 is maintained over the application period of the first hold element p2. Subsequently, the piezoelectric element 29 is bent inward of the pressure chamber 38 by the first contraction element p3, and the pressure chamber 38 rapidly contracts from the expansion volume corresponding to the first expansion potential E1 to the contraction volume corresponding to the contraction potential E2. To do. Due to the rapid contraction of the pressure chamber 38, the ink in the pressure chamber 38 is pressurized and pressure vibration is generated, whereby the ink in the pressure chamber 38 and the nozzle 37 is agitated. The expansion state of the pressure chamber 38 is maintained over the application period of the second hold element p4, and then the piezoelectric element 29 is deflected to the outside of the pressure chamber 38 by the second expansion element p5, and the pressure chamber 38 contracts. It expands again from the volume to the expansion volume. Subsequently, the contracted state of the pressure chamber 38 is maintained over the application period of the third hold element p6. After the third hold element p6, the piezoelectric element 29 returns to the initial position by the second contraction element p7, and the volume of the pressure chamber 38 returns to the reference volume.

  By performing the micro-vibration operation by such third micro-vibration pulse Pv3, the volume of the pressure chamber 38 can be changed more greatly by the first contraction element p3 and the second expansion element p5. The highest ink stirring effect can be obtained as compared with the case of the fine vibration pulse. Further, the second expansion element p5 and the second contraction element p7 can function as waveform elements that suppress the pressure vibration generated in the pressure chamber 38. For this reason, since the movement of the meniscus after the micro-vibration operation by the third micro-vibration pulse Pv3 is suppressed, it is possible to ensure the ink ejection stability in the subsequent ejection operation.

  Here, in this embodiment, regarding the timing at which the first contraction element p3 is applied to the piezoelectric element 29, the timing at which the pressure vibration generated when the pressure chamber 38 is expanded by the first expansion element p1 can be excited. It is set to become. Specifically, as shown in FIG. 4, the time Δt1 from the start end of the first expansion element p1 to the start end of the first contraction element p3 is the period of the pressure vibration generated in the ink in the pressure chamber 38 (natural vibration). Period) is set to be 1/2 of Tc. As a result, the pressure vibration having the same phase as the pressure vibration generated by the first expansion element p1 is excited by the first contraction element p3, so that the vibrations are strengthened, thereby further enhancing the ink stirring effect. be able to. Further, the second expansion element p5 is configured to be applied to the piezoelectric element 29 at a timing at which pressure vibration generated by the first contraction element p3 is suppressed. Specifically, the time Δt2 from the start end of the first contraction element p3 to the start end of the second expansion element p5 is set to be equal to the natural vibration period Tc (or a natural number multiple of Tc). As a result, the pressure vibration having an opposite phase to the pressure vibration generated by the first contraction element p3 is excited by the second expansion element p5, so that the vibrations are weakened and thereby the first contraction element p3 The generated pressure vibration can be suppressed. The second expansion element p5 changes from the contraction potential E2 to the expansion potential E1, so that the pressure vibration generated by the first contraction element p3 is suppressed, while the pressure vibration by the second expansion element p5 is suppressed. As a result, an ink stirring effect can be obtained. Similarly, the second contraction element p7 is configured to be applied to the piezoelectric element 29 at a timing at which the pressure vibration generated by the second expansion element p5 is suppressed. That is, the time Δt3 from the start end of the second expansion element p5 to the start end of the second contraction element p7 is set to be equal to the natural vibration period Tc (or a natural number multiple of Tc). As a result, the pressure vibration having the opposite phase to the pressure vibration generated by the second expansion element p5 is excited by the second contraction element p7, so that the pressure vibration generated by the second expansion element p5 is suppressed. can do.

By adopting such a configuration, in particular, in the fine vibration operation by the second fine vibration pulse Pv2 and the third fine vibration pulse Pv3, the pressure vibration is generated while the ink in the nozzle 37 and the pressure chamber 38 is effectively stirred. Reduced. Accordingly, even when ink is ejected in the period following the period in which the micro-vibration operation is performed, the influence of residual vibration after the micro-vibration operation is suppressed, so that it is possible to ensure ejection stability. Become. With respect to Δt1 to Δt3, the values are not limited to the exemplified values, and when the pressure agitation effect is increased to improve the ink stirring effect, the value is set to ½ of Tc, and the residual vibration is suppressed to suppress the ejection stability. In order to improve the value, it may be set to n × Tc (n: natural number).
Here, the above Tc can be generally expressed by the following equation.
Tc = 2π√ [(Mn + Ms) / (Mn × Ms × (Cc + Ci))]
In the above equation, Mn is an inertance in the nozzle 37 (mass of ink per unit cross-sectional area), Ms is an inertance in the individual communication port 39, and Cc is compliance of the pressure chamber 38 (volume change per unit pressure, degree of softness) Ci) is the ink compliance (Ci = volume V / [density ρ × sound speed c ² ]).

  FIG. 8 is a table showing a selection example of the micro-vibration pulse with respect to the idle running time and the effect of the intermittent ability and the discharge stability in that case. Example 1 in FIG. 8 shows an example in which the fine vibration operation is performed by selecting the first fine vibration pulse Pv1 when the idle travel time Ti for the predetermined nozzle 37 is 2.5 seconds. . When the idling time Ti is 2.5 seconds, the degree of ink thickening is relatively slight. Therefore, the ink agitation effect of the micro-vibration operation by the first micro-vibration pulse Pv1 causes the subsequent ejection operation (particularly, In the discharge operation in the period following the period in which the fine vibration operation is performed, discharge failure due to ink thickening is prevented (◯). Further, in the micro-vibration operation by the first micro-vibration pulse Pv1, the residual vibration is reliably converged by the next cycle, so that the ejection failure due to the residual vibration is prevented and the ejection stability is improved (◯ ). On the other hand, as in the case of Example 2 and Example 3, when the idle time Ti is 5.0 seconds or longer, the thickened ink can be sufficiently stirred in the fine vibration operation by the first fine vibration pulse Pv1. However, although ejection stability is good (◯), ejection failure due to ink thickening occurs in subsequent ejection operations (×).

  Example 4 shows an example in which the fine vibration operation is performed with the second fine vibration pulse Pv2 selected when the idle time Ti is 5.0 seconds. The second micro-vibration pulse Pv2 has a higher agitation effect in the micro-vibration operation than the first micro-vibration pulse Pv1, and thus increases the viscosity of the ink even when the idling time Ti is 5.0 seconds. The resulting discharge failure is prevented (◯). Further, the residual vibration is suppressed by the pre-stage expansion element p5a as the vibration damping element, and the thickened ink suppresses the residual vibration due to its viscous resistance, so that the ejection stability is also good (◯). However, as in the case of Example 5, when the idle time Ti is 10.0 seconds or more, the ink thickening further proceeds. Therefore, in the fine vibration operation by the second fine vibration pulse Pv2, the thickened ink is sufficient. In the subsequent discharge operation, discharge failure due to ink thickening occurs (×).

  Example 6 shows an example in which the fine vibration operation is performed by selecting the third fine vibration pulse Pv3 when the idle time Ti is 5.0 seconds. Since the third fine vibration pulse Pv3 has the highest stirring effect in the fine vibration operation among the fine vibration pulses, the thick ink is sufficiently stirred even when the idling time Ti is 5.0 seconds. And ejection failure due to ink thickening is prevented (◯). In addition, the second expansion element and the second contraction element p7 function as a vibration damping element, and the ink that has been thickened as described above does not easily vibrate, so that the ejection stability is also good (◯). Further, even in the case where the idle time Ti is 10.0 seconds as in the case of Example 7, in the fine vibration operation by the third fine vibration pulse Pv3, ejection failure due to ink thickening is prevented (◯ ) In addition, the result that the ejection stability is good (◯) was obtained. As in Example 8, when the idle time Ti is 2.5 seconds, that is, when the ink thickening has not progressed so much, the above-mentioned third fine vibration pulse Pv3 is selected and the fine vibration operation is performed. If this is done, the ink will be stirred more than necessary, resulting in an increased residual vibration. In this case, ejection failure due to ink thickening is prevented (◯), but ejection stability deteriorates (×). For this reason, in order to prevent ejection failure due to ink thickening and improve intermittent performance and to achieve both ejection stability, fine vibration operation with a more optimal vibration drive pulse according to idle running time Ti It is important to do.

  FIG. 9 is a flowchart for explaining the selection process of the minute vibration pulse. In the printer 1 according to the present invention, a threshold is set in advance for the idle time based on the result shown in FIG. 8, and any of the drive signals COMvb is selected based on the result of comparing the threshold and the idle time for each nozzle 37. The fine vibration pulses Pv1 to Pv3 are selectively applied to the piezoelectric element 29 corresponding to the nozzle 37 to perform a fine vibration operation. Specifically, for example, 4 seconds is set as the first threshold th1, and 8 seconds is set as the second threshold th2. Then, the idle time is counted for each nozzle 37 during the recording operation, and the following processing is performed for the nozzle 37 that does not discharge ink at a predetermined recording period. That is, first, it is determined whether or not the idling time Ti exceeds the first threshold th1 (step S1), and when it is determined that the idling time Ti does not exceed the threshold th1 (Ti ≦ th1) (No In this recording cycle, the first fine vibration pulse Pv1 is selected and applied to the piezoelectric element 29 corresponding to the nozzle 37 to perform the fine vibration operation (step S2). On the other hand, when it is determined that the idle time Ti has exceeded the threshold th1 (Ti> th1) (Yes), it is subsequently determined whether the idle time Ti has exceeded the second threshold th2 (step) S3). When it is determined that the idling time Ti does not exceed the threshold th2 (th1 <Ti ≦ th2) (No), the second micro-vibration pulse Pv2 is selected in the current recording cycle, and the piezoelectric element corresponding to the nozzle 37 29 is applied to perform a fine vibration operation (step S4). On the other hand, when it is determined that the idle time Ti has exceeded the threshold th2 (Ti> th2) (Yes), the third micro-vibration pulse Pv3 is selected in the current recording cycle, and the piezoelectric element 29 corresponding to the nozzle 37 is selected. Is applied to the micro-vibration operation (step S5).

  As described above, any of the micro-vibration pulses Pv1 to Pv3 in the drive signal COMvb is selectively applied to the piezoelectric element 29 in accordance with the idle time Ti in the recording operation. Depending on the degree of viscosity, a more appropriate fine vibration operation is executed without excess or deficiency. As a result, it is possible to improve the intermittent capability and ensure the ejection stability. Further, since the intermittent capability is improved, the frequency of executing the recovery process such as the flushing operation and the cleaning operation can be reduced, so that the consumption of ink can be suppressed correspondingly.

  In the first embodiment, the first micro-vibration pulse Pv1 to the third micro-vibration are determined according to the comparison result between the first threshold value th1 and the second threshold value th2 and the idling time Ti for each nozzle 37. Although the configuration in which one of the three pulses Pv3 is selected and the micro-vibration operation is performed is illustrated, the present invention is not limited to this. For example, one threshold is set for the idle running time, and the threshold and each nozzle 37 are set. Depending on the comparison result with the idle travel time Ti, either the second fine vibration pulse Pv2 or the third fine vibration pulse Pv3 may be selected to perform the fine vibration operation. That is, in this configuration, when the idle running time Ti of the nozzle 37 is equal to or less than a predetermined threshold value, the second fine vibration pulse Pv2 is selected and applied to the piezoelectric element 29 corresponding to the nozzle 37, while When the travel time Ti exceeds the threshold value, the third fine vibration pulse Pv3 is selected and applied to the piezoelectric element 29 corresponding to the nozzle 37, and the fine vibration operation is performed.

Further, in the above embodiment, by selecting a part of the pulse parts P1 to P3 or a combination thereof in the same drive signal COMvb, the first fine vibration pulse Pv1, the second fine vibration pulse Pv2, and the third Although the configuration in which the minute vibration pulse Pv3 is applied to the piezoelectric element 29 is illustrated, the present invention is not limited to this. For example, the first micro-vibration pulse Pv1, the second micro-vibration pulse Pv2, and the third micro-vibration pulse Pv3 are included in different drive signals, and one of these drive signals is compared with the idle time and the threshold value. The configuration may be selected based on the above and applied to the piezoelectric element 29.
Furthermore, it is possible to employ a configuration in which these micro-vibration pulses are included in a drive signal that includes drive pulses related to ink ejection.

  In the above-described embodiment, the so-called flexural vibration type piezoelectric element 29 is illustrated as the piezoelectric element. However, the piezoelectric element is not limited to this, and for example, a so-called longitudinal vibration type piezoelectric element can be employed. In this case, with respect to each micro-vibration pulse exemplified in the above embodiment, the waveform is a waveform in which the direction of potential change, that is, up and down (polarity) is inverted.

  The present invention is not limited to the above-described printer as long as it is a liquid ejecting apparatus that performs a micro-vibration operation. Various ink jet recording apparatuses such as a plotter, a facsimile machine, and a copying machine, or a cloth that is a kind of landing target Also applicable to textile printing devices that perform printing by landing ink from the liquid ejection head on the (material to be printed), or liquid ejection devices other than recording devices, such as display manufacturing devices, electrode manufacturing devices, chip manufacturing devices, etc. can do.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... External device, 3 ... Paper feed mechanism, 4 ... Carriage moving mechanism, 5 ... Linear encoder, 6 ... Recording head, 7 ... Printer controller, 8 ... Interface, 9 ... Main control circuit, 10 ... Memory | storage part , 11 ... Drive signal generation circuit, 12 ... Platen, 13 ... Print engine, 15 ... Head controller, 16 ... Carriage, 17 ... Ink cartridge, 18 ... Guide rod, 20 ... Capping mechanism, 21 ... Cap, 22 ... Wiping mechanism, DESCRIPTION OF SYMBOLS 23 ... Wiper, 25 ... Nozzle plate, 26 ... Communication board | substrate, 27 ... Pressure chamber formation board | substrate, 28 ... Elastic film, 29 ... Piezoelectric element, 30 ... Protection board, 31 ... Piezoelectric device, 32 ... Case, 33 ... Housing empty part , 34 ... Ink introduction path, 35 ... Common liquid chamber, 37 ... Nozzle, 38 ... Pressure chamber, 39 ... Individual communication port

Claims (2)

A liquid ejection head that has a nozzle that ejects liquid, a pressure chamber that communicates with the nozzle, and an actuator that generates pressure vibration in the liquid in the pressure chamber, and that ejects liquid from the nozzle by driving the actuator;
A drive pulse generation circuit that drives the actuator to generate a vibration drive pulse that vibrates the liquid in the pressure chamber and the nozzle;
The drive pulse generation circuit alternately changes the polarity of the potential change from the reference potential and the first vibration drive pulse in which the potential is changed three times in total and returns to the reference potential. And a second vibration drive pulse that changes the potential a total of four times and returns to the reference potential.
When the elapsed time in the non-ejection state in which no liquid is ejected after the ejection process is started or after the previous ejection of liquid in the ejection process is less than or equal to a predetermined threshold, While one vibration drive pulse is selected and applied to the actuator corresponding to the nozzle, if the elapsed time exceeds the threshold, the second vibration drive pulse is selected and applied to the actuator corresponding to the nozzle. And a liquid ejection device characterized by performing a fine vibration operation. The drive pulse generation circuit is capable of generating a third vibration drive pulse in which the potential changes alternately from the reference potential and the potential changes twice in total and returns to the reference potential.
If the elapsed time is less than or equal to the first threshold, the third vibration drive pulse is selected and applied to the actuator corresponding to the nozzle,
When the elapsed time exceeds the first threshold and is equal to or less than a second threshold that is longer than the first threshold, the first vibration drive pulse is selected and applied to the actuator corresponding to the nozzle. 2. The liquid ejection apparatus according to claim 1, wherein when the elapsed time exceeds the second threshold, the second vibration driving pulse is selected and applied to an actuator corresponding to the nozzle.

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