JP2012240257A - Liquid ejection device and control method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejection device that allows liquid, ejected from a nozzle, to land on a prescribed member in flushing operation in order to prevent the liquid from being deposited on another member in the device, and a control method for the same.SOLUTION: The liquid ejection device includes: a liquid jet head 2 that ejects liquid from a nozzle 30 toward a landing target 6; a support means 5 that is arranged spaced apart with respect to a nozzle forming surface of the liquid jet head 2 when executing ejection operation and supports the landing target 6; a liquid-droplet collecting means 13 that is arranged at a position outside an ejection region in the support means 5 in which liquid is ejected to the landing target 6 from the liquid jet head 2; a voltage applied part 15 provided in the liquid-droplet collecting means 13; and a voltage applying means 58 for applying a voltage to the voltage applied part 15. After flushing operation to eject liquid from the liquid jet head 2 toward the liquid-droplet collecting means 13, the voltage applying means 58 applies a voltage to the voltage applied part 15.

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 ejects liquid in a pressure chamber from a nozzle by driving a pressure generating unit, and a control method therefor.

  The liquid ejecting apparatus includes a liquid ejecting head and ejects various liquids from the ejecting head. As this liquid ejecting apparatus, for example, there is an image recording apparatus such as an ink jet printer or an ink jet plotter, but recently, various types of manufacturing have been made by taking advantage of the ability to accurately land a very small amount of liquid 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.

  In recent years, recording heads used in the above printers tend to reduce the amount of ink ejected from nozzles in order to meet demands for image improvement and the like. In order to land such a small amount of droplets reliably on the recording medium, the initial velocity of the droplets is set to be relatively high. As a result, the droplets ejected from the nozzle are stretched during the flight, and separated into a leading main droplet (main droplet) and a satellite droplet (sub-droplet) after that. Some or all of the satellite droplets may suddenly decrease in speed due to the viscous resistance of air, and may become mist without reaching the recording medium. The mist of satellite droplets (mist) contaminates the inside of the apparatus and has a problem of causing malfunction due to adhesion to easily charged members such as a recording head and an electric circuit. Such a problem occurs not only during a recording operation in which droplets are ejected onto a recording medium, but also on the ink receiving member located at a position away from the recording medium in order to forcibly discharge the thickened liquid or bubbles. It occurs in the same manner during the flushing operation for injecting. In particular, since the thickened liquid is easily stretched during flight, the flushing operation is more likely to generate mist.

  In order to prevent such inconvenience, the recording member is charged with the droplets ejected from the nozzles and absorbs the droplets provided on the support member (or platen) that supports the recording medium during recording, and the recording head. Attempts have been made to surely land the mist on the absorbing member by forming an electric field with the nozzle forming surface (see, for example, Patent Document 1). In addition, there is an apparatus in which an electrode member is disposed inside a cap member, and flushing is performed in a state where an electric field is formed between the electrode member and a nozzle formation surface of a recording head (for example, see Patent Document 2).

JP 2010-173324 A JP 2009-90630 A

  However, as shown in the schematic diagram of FIG. 14A, in the process in which the ink ejected from the nozzle 80 of the recording head extends toward the electrode member 81, electrostatic induction from the positively charged electrode member 81 causes Negative charges are induced in the head portion close to the electrode member 81 (portion that becomes the main liquid droplet Md), while positive charges are induced in the rear end portion on the side close to the nozzle 80 opposite to this. Be guided. Then, as shown in FIG. 14B, the ink ejected from the nozzle is separated into, for example, a main droplet Md, a first satellite droplet Sd1, and a second satellite droplet (mist) Sd2. In this case, the main droplet Md is negatively charged, the second satellite droplet Sd2 is positively charged, and the first satellite droplet Sd1 is uncharged. In this case, even if the main droplet Md and the first satellite droplet Sd1 land on the electrode member 81, the second satellite droplet Sd2 repels the positively charged electrode member 81 to form the nozzle of the recording medium. Mist drifts near the surface. Part of this mist adheres to the nozzle forming surface. When mist adheres to the nozzle forming surface, it is necessary to periodically wipe the nozzle forming surface with a wiping member. Further, the mist that has not adhered to the nozzle forming surface may adhere to and contaminate the printer component having a polarity different from that of the mist.

  By the way, in order to prevent charging of the ink, a configuration in which an electric field is not formed between the nozzle forming surface and the electrode member is conceivable. However, even when ink is ejected from the nozzle in this configuration, the ejected ink is not It turns out to be charged. That is, the ink ejected from the nozzles tends to be positively charged due to the Leonard effect while flying toward the electrode member. That is, when the ink is charged, positive charges are collected at the central portion of the droplet, while negative charges are collected at the surface layer portion. Then, the droplets gradually become positive due to evaporation and splitting of the surface layer portion during the flight. As described above, even in a configuration in which an electric field is not formed between the nozzle formation surface and the electrode member, the ink ejected from the nozzle is charged, so that the mist adheres to the nozzle formation surface and the components of the printer. Has occurred.

  The phenomenon as described above is not limited to the piezoelectric vibrator, and similarly occurs in other pressure generating means that operate by applying a driving voltage, such as a heating element.

  The present invention has been made in view of such circumstances, and an object thereof is to cause liquid ejected from a nozzle to land on a predetermined member in a flushing operation, and the liquid adheres to other members in the apparatus. An object of the present invention is to provide a liquid ejecting apparatus that can prevent this, and a control method therefor.

The liquid ejecting apparatus of the present invention has been proposed in order to achieve the above-described object, and is connected to the nozzle by being driven by application of a drive signal and a nozzle forming surface on which a nozzle for ejecting liquid is formed. A liquid ejecting head having pressure generating means for causing pressure fluctuation in the liquid in the pressure chamber, and ejecting the liquid from the nozzle toward the landing target by driving the pressure generating means;
A support unit that is disposed at an interval with respect to the nozzle formation surface of the liquid jet head when performing the jetting operation, and supports the landing target;
Droplet collecting means disposed at a position outside the ejection region in the support means for ejecting liquid from the liquid ejecting head to the landing target;
A voltage applied portion provided in the droplet collecting means;
Voltage applying means for applying a voltage to the voltage applied portion;
With
The voltage applying unit applies a voltage to the voltage application portion after a flushing operation of ejecting liquid from the liquid ejecting head toward the droplet collecting unit.

  According to the present invention, since no voltage is applied to the voltage application part during the flushing operation, it is possible to prevent the mist from being charged with the same polarity as the voltage application part due to electrostatic induction, and the voltage application after the flushing operation is completed. By applying a voltage to the application unit, it is possible to collect mist in the voltage application unit. Thereby, it is reduced that these mist adheres to other components (for example, a motor, a drive belt, a linear scale, etc.) in an apparatus. As a result, failure due to mist adhesion is suppressed, and durability and reliability of the liquid ejecting apparatus are improved.

In the above configuration, the flushing operation has at least two short-term flushing operations,
It is preferable that the voltage applying unit applies a voltage to the voltage application part after one short-term flushing operation and before the next short-term flushing operation.

  According to this configuration, by applying a voltage to the voltage application unit every time the short-term flushing operation is completed, scattering of mist can be prevented, and the mist can be more reliably collected in the voltage application unit. .

  In each of the above configurations, it is preferable that the voltage applying unit applies a negative voltage to the voltage application portion.

  According to this configuration, when the mist is positively charged (plus) due to the Leonard effect, it is possible to collect the mist at the voltage application portion.

  Moreover, it is desirable that the conductivity of the liquid is 10 (mS / cm) or less.

  According to this configuration, the amount of mist charge due to the Leonard effect can be increased, and the mist can be more reliably collected at the voltage application portion.

  In the above configuration, it is desirable that the intensity of the electric field from the voltage application portion toward the nozzle formation surface is 160 (V / mm) or more.

  According to this configuration, even when the positive charge amount due to the Leonard effect is small, it is possible to more reliably collect mist at the voltage application portion.

The control method of the liquid ejecting apparatus according to the present invention causes pressure fluctuations in the nozzle forming surface on which the nozzle for ejecting the liquid is formed, and in the liquid in the pressure chamber that is driven by application of the drive signal and communicates with the nozzle. A liquid ejecting head for ejecting liquid from the nozzle toward the landing target by driving the pressure generating means;
A support unit that is disposed at an interval with respect to the nozzle formation surface of the liquid jet head when performing the jetting operation, and supports the landing target;
Droplet collecting means disposed at a position outside the ejection region in the support means for ejecting liquid from the liquid ejecting head to the landing target;
A voltage applied portion provided in the droplet collecting means;
Voltage applying means for applying a voltage to the voltage applied portion;
A liquid ejecting apparatus control method comprising:
The voltage applying unit applies a voltage to the voltage application portion after a flushing operation of ejecting liquid from the liquid ejecting head toward the droplet collecting unit.

In the control method, the flushing operation includes at least two short-term flushing operations,
It is preferable that the voltage applying unit applies a voltage to the voltage application part after one short-term flushing operation and before the next short-term flushing operation.

FIG. 3 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view of a main part of the recording head. It is sectional drawing explaining the structure of a piezoelectric vibrator. FIG. 2 is a block diagram illustrating an electrical configuration of a recording head. It is a timing chart explaining the flushing operation and the voltage control of the voltage generator. It is a wave form diagram explaining the structure of an ejection drive pulse. (A) The figure explaining the collection of mist when there is a recording head above the flushing box, (b) The figure explaining the collection of mist when there is no recording head above the flushing box. It is a graph showing the relationship between the electrical conductivity of a droplet and the charge amount by the Leonard effect. It is a graph showing the relationship between the dwell time of a droplet and the charge amount by the Leonard effect. It is a graph showing the relationship between the charged amount of a droplet and the droplet recovery rate by electrolysis. It is a timing chart explaining the flushing operation | movement and ON / OFF control of a voltage generation part in 2nd Embodiment. It is a figure explaining the structure of the flushing box in 3rd Embodiment. It is a figure explaining the structure of the flushing box in 4th Embodiment. FIG. 6 is a schematic diagram illustrating a state in which ink ejected from a nozzle is charged in a configuration in which an electric field is formed between the nozzle and an electrode member.

  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 description, an ink jet recording apparatus 1 (hereinafter referred to as a printer) will be described as an example of the liquid ejecting apparatus of the invention.

  FIG. 1 is a perspective view showing the configuration of the printer 1. The printer 1 is provided with a recording head 2 as a kind of liquid ejecting head and a carriage 4 to which an ink cartridge 3 as a kind of liquid supply source is detachably attached, and below the recording head 2 during a recording operation. A platen 5 (corresponding to support means in the present invention) disposed, a flushing box 13 (corresponding to droplet collecting means in the present invention) disposed below the recording head 2 during the flushing operation, and a carriage 4 A carriage moving mechanism 7 for reciprocating the recording paper 6 (a recording medium and a landing target) in the paper width direction, that is, the main scanning direction, and a transport mechanism for transporting the recording paper 6 in the sub-scanning direction orthogonal to the main scanning direction. 8 and.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and a detection signal, that is, an encoder pulse (a kind of position information) is transmitted to the printer controller 51 (see FIG. 4). The linear encoder 10 is a kind of position information output means, and outputs an encoder pulse EP corresponding to the scanning position of the recording head 2 as position information in the main scanning direction.

  A home position serving as a base point for scanning of the carriage is set in an end area outside the recording area within the movement range of the carriage 4. A capping member 11 for sealing the nozzle forming surface (nozzle plate 24: see FIG. 2) of the recording head 2 and a wiper member 12 for wiping the nozzle forming surface are disposed at the home position in the present embodiment. Yes. The printer 1 is bi-directional between when the carriage 4 moves from the home position toward the opposite end and when the carriage 4 returns from the opposite end to the home position. So-called bidirectional recording in which characters, images, etc. are recorded on the recording paper 6 is possible.

  The platen 5 is disposed at a distance from the nozzle formation surface of the recording head 2 when performing the ejection operation, and supports the recording paper 6. In the present embodiment, it is formed in a plate shape that is long in the main scanning direction, and a plurality of support protrusions 5a protrude from the surface at predetermined intervals along the longitudinal direction. Each support protrusion 5a protrudes above the platen surface (on the recording head 2 side during recording operation). The upper surface of each support protrusion 5a serves as an abutting surface that supports the recording paper 6, and partially supports the rear surface of the recording paper 6 (the surface opposite to the recording surface on which ink is landed). In addition, an ink absorbing member 5b is disposed on the surface of the platen 5 at a portion removed from each support protrusion 5a. The ink absorbing member 5b is made of a porous member having a liquid absorbing property made of, for example, felt or urethane sponge.

  Further, the end of the platen 5 in the main scanning direction, more specifically, an area outside the area (ink ejection area) where ink is ejected onto the recording paper 6 on the platen 5, more specifically, the main area rather than the ink ejection area. It is an area outside the scanning direction, and is larger than the end in the width direction (maximum recording paper width) of the recording paper 6 when the maximum recording paper 6 that the printer 1 can handle is arranged on the platen 5. A flushing box 13 for collecting ink ejected from the recording head 2 in the flushing operation is provided at a position on the outer side. The flushing boxes 13 are desirably provided on both sides of the platen 5 in the main scanning direction, but may be provided on at least one side. As shown in FIG. 7A, the flushing box 13 in the present embodiment is formed in a box shape that opens upward (on the recording head 2 side), and the bottom surface of the flushing box 13 is made of, for example, urethane sponge. Ink absorbing material 14 is provided. Note that the flushing box 13 in the present embodiment is grounded. In addition, inside the ink absorbing material 14, the electrode wire 15 (to the voltage application portion in the present invention) with the upper portion exposed from the ink absorbing material 14 over the width of the bottom surface of the flushing box 13 in the sub-scanning direction. Equivalent). The electrode wire 15 is formed of a metal or the like in a string shape or a rod shape, and is configured to be applied with a voltage from a voltage generation unit 58 described later. The flushing operation and the application of voltage to the electrode line 15 will be described later. Further, the electrode wire 15 can be formed in a mesh shape by being folded back multiple times.

  FIG. 2 is a cross-sectional view of a main part for explaining the configuration of the recording head 2. The recording head 2 includes a case 16, a vibrator unit 17 housed in the case 16, a flow path unit 18 joined to the bottom surface (tip surface) of the case 16, a cover member 45, and the like. . The case 16 is made of, for example, an epoxy resin, and a storage space 19 for storing the vibrator unit 17 is formed in the case 16. The vibrator unit 17 includes a piezoelectric vibrator 20 that functions as a kind of pressure generating means, a fixed plate 21 to which the piezoelectric vibrator 20 is joined, and a flexible cable 22 that supplies a drive signal to the piezoelectric vibrator 20. ing.

  FIG. 3 is a cross-sectional view in the element longitudinal direction for explaining the configuration of the vibrator unit 17. As shown in the figure, the piezoelectric vibrator 20 is a laminated piezoelectric vibrator 20 formed by alternately laminating a piezoelectric body 41 with a common internal electrode 39 and individual internal electrodes 40. Here, the common internal electrode 39 is an electrode common to all the piezoelectric vibrators 20 and is set to the ground potential. The individual internal electrode 40 is an electrode whose potential varies according to the ejection drive pulse DP (see FIG. 6) of the applied drive signal. In this embodiment, the free end portion 20a is a portion of the piezoelectric vibrator 20 from the vibrator tip to about half or about two thirds of the vibrator longitudinal direction (direction orthogonal to the stacking direction). Yes. The remaining part of the piezoelectric vibrator 20, that is, the part from the base end of the free end 20a to the vibrator base end is a base end 20b.

  An active region (overlap portion) A in which the common internal electrode 39 and the individual internal electrode 40 overlap each other is formed at the free end 20a. When a potential difference is applied to these internal electrodes, the piezoelectric body 41 in the active region A is activated and deformed, and the free end portion 20a is displaced in the longitudinal direction of the vibrator to expand and contract. The base end of the common internal electrode 39 is electrically connected to the common external electrode 42 at the base end face portion of the piezoelectric vibrator 20. On the other hand, the tip of the individual internal electrode 40 is electrically connected to the individual external electrode 43 at the tip surface portion of the piezoelectric vibrator 20. Note that the distal end of the common internal electrode 39 is positioned slightly in front of the distal end surface portion of the piezoelectric vibrator 20 (base end surface side), and the proximal end of the individual internal electrode 40 is the boundary between the free end portion 20a and the proximal end portion 20b. Is located.

  The individual external electrode 43 is an electrode formed in series on the tip surface portion of the piezoelectric vibrator 20 and a wiring connection surface (upper face in FIG. 3) that is one side surface of the piezoelectric vibrator 20 in the stacking direction. The wiring pattern of the flexible cable 22 as a member is electrically connected to each individual internal electrode 40. And the part by the side of the wiring connection surface of this separate external electrode 43 is continuously formed toward the front end side from the base end part 20b. The common external electrode 42 is formed on the base end face portion of the piezoelectric vibrator 20, the above-described wiring connection face, and a fixing plate mounting face (lower face in FIG. 3) which is the other side face of the piezoelectric vibrator 20 in the stacking direction. These are electrodes formed in series, and conduct between the wiring pattern of the flexible cable 22 and each common internal electrode 39. The portion on the wiring connection surface side of the common external electrode 42 is continuously formed from a little before the end portion of the individual external electrode 43 toward the base end surface portion side, and the portion on the fixed portion mounting surface side is It is continuously formed from a position slightly ahead of the distal end surface portion of the vibrator toward the proximal end side.

  The base end portion 20b is a non-operation portion that does not expand and contract even when the piezoelectric body 41 in the active region A is operated. The flexible cable 22 is arranged on the wiring connection surface side of the base end portion 20b, and the individual external electrode 43 and the common external electrode 42 and the flexible cable 22 are electrically connected on the base end portion 20b. A drive signal is applied to each individual external electrode 43 through the flexible cable 22.

  The flow path unit 18 is configured by joining a nozzle plate 24 to one surface of the flow path forming substrate 23 and a diaphragm 25 to the other surface of the flow path forming substrate 23. The flow path unit 18 is provided with a reservoir 26 (common liquid chamber), an ink supply port 27, a pressure chamber 28, a nozzle communication port 29, and a nozzle 30. A series of ink flow paths from the ink supply port 27 to the nozzle 30 through the pressure chamber 28 and the nozzle communication port 29 are formed corresponding to each nozzle 30.

  The nozzle plate 24 is a thin plate made of metal such as stainless steel in which a plurality of nozzles 30 are formed in a row at a pitch (for example, 180 dpi) corresponding to the dot formation density. The nozzle plate 24 is provided with a plurality of nozzle rows (nozzle groups) by arranging nozzles 30, and one nozzle row is composed of, for example, 180 nozzles 30. The surface of the nozzle plate 24 on the side where ink is ejected corresponds to the nozzle formation surface in the present invention.

  The diaphragm 25 has a double structure in which an elastic film 32 is laminated on the surface of the support plate 31. In the present embodiment, the vibration plate 25 is manufactured using a composite plate material in which a stainless steel plate, which is a kind of metal plate, is used as the support plate 31 and a resin film is laminated on the surface of the support plate 31 as an elastic film 32. The diaphragm 25 is provided with a diaphragm 33 that changes the volume of the pressure chamber 28. The diaphragm 25 is provided with a compliance portion 34 that seals a part of the reservoir 26.

  The diaphragm 33 is produced by partially removing the support plate 31 by etching or the like. That is, the diaphragm portion 33 includes an island portion 35 to which the tip end surface of the free end portion 20 a of the piezoelectric vibrator 20 is joined and a thin elastic portion surrounding the island portion 35. The compliance part 34 is produced by removing the support plate 31 in the region facing the opening surface of the reservoir 26 by etching processing or the like in the same manner as the diaphragm part 33, and the pressure fluctuation of the liquid stored in the reservoir 26 is reduced. Functions as a damper to absorb.

  Since the tip surface of the piezoelectric vibrator 20 is joined to the island portion 35, the volume of the pressure chamber 28 can be changed by expanding and contracting the free end portion 20a of the piezoelectric vibrator 20. As the volume changes, pressure fluctuations occur in the ink in the pressure chamber 28. The recording head 2 ejects ink from the nozzles 30 using this pressure fluctuation.

  The cover member 45 is a member that protects the side surface of the flow path unit 18 and the side surface of the head case 16, and is made of a conductive plate material such as stainless steel. A part of the cover member 45 in this embodiment is in contact with the peripheral portion of the nozzle forming surface in a state where the nozzle 30 of the nozzle plate 24 is exposed, and is electrically connected to the nozzle plate 24. . The cover member 45 is grounded, and is brought into contact with the nozzle plate 24 so as to be conductive. For example, static electricity generated from the recording paper 6 or the like is transmitted through the nozzle plate 24, damage to the driving IC, or the like. It is designed to prevent charging.

Next, the electrical configuration of the printer 1 will be described.
FIG. 4 is a block diagram illustrating the electrical configuration of the printer 1. The external device 50 is an electronic device that handles images, such as a computer or a digital camera. The external device 50 is communicably connected to the printer 1 and transmits print data corresponding to the image or the like to the printer 1 so that the printer 1 prints an image or text on a recording medium such as the recording paper 6. .

  The printer 1 in this embodiment includes a transport mechanism 8, a carriage moving mechanism 7, a linear encoder 10, a recording head 2, an electrode line 15, and a printer controller 51.

  The printer controller 51 is a control unit for controlling each unit of the printer 1, and includes an interface (I / F) unit 54, a CPU 55, a storage unit 56, and a drive signal generation unit 57. The interface unit 54 transmits and receives data to and from the printer 1 such as receiving print data and print commands transmitted from the external device 50 to the printer 1, and transmitting status information of the printer 1 to the external device 50. . The CPU 55 is an arithmetic processing device for controlling the entire printer 1. The memory | storage part 56 is an element which memorize | stores the data used for the program and various control of CPU55, and contains ROM, RAM, and NVRAM (nonvolatile memory element). The CPU 55 controls each unit according to a program stored in the storage unit 56.

  The CPU 55 functions as a timing pulse generator that generates a timing pulse PTS from the encoder pulse EP output from the linear encoder 10. Then, the CPU 55 controls the transfer of print data, the generation of the drive signal COM by the drive signal generation unit 57, and the like in synchronization with the timing pulse PTS. Further, the CPU 55 generates a timing signal such as a latch signal LAT based on the timing pulse PTS and outputs the timing signal to the head controller 53 of the recording head 2. The head controller 53 controls the application of the ejection drive pulse DP (see FIG. 6) of the drive signal COM to the piezoelectric vibrator 20 of the recording head 2 based on the head control signal (print data and timing signal) from the printer controller 51. I do.

  The voltage generator 58 (corresponding to the voltage applying means in the present invention) is a power source that generates a voltage to be applied to the electrode wire 15 of the flushing box 13. In this embodiment, the electrode wire 15 is configured to be negatively charged by applying a negative voltage. The voltage generator 58 is controlled to be turned on / off by the CPU 55. Specifically, as shown in FIG. 5, the recording head 2 moves above the flushing box 13 and performs a flushing operation in which the liquid is ejected from the nozzle 30 toward the flushing box 13 once or a plurality of times. During the period Tf, the voltage generator 58 is turned off. When the flushing operation period Tf ends, the voltage generator 58 is switched to the ON state. In the present embodiment, the voltage generator 58 is switched to the on state for the voltage application period Te immediately after the flushing operation period Tf ends. As a result, a voltage is applied to the electrode line 15 and an electric field is formed between the electrode line 15 and the nozzle formation surface of the recording head 2 (see FIG. 7A). The line is schematically represented.) Further, when the recording head 2 moves to a position off the upper side of the flushing box 13, in addition to the electrode lines 15 and the nozzle forming surface of the moved recording head 2, members constituting the printer 1 (for example, guide rods, drive An electric field is formed between the belt, the linear scale and the casing) and the flushing box 13 (see FIG. 7B. The broken lines schematically represent the lines of electric force). It should be noted that the timing for switching the voltage generator 58 to the on state may take some time after the flushing operation period Tf. In short, the voltage generation unit 58 may be switched on after the flushing operation (continuously as a series of processes). The period Te for turning on the voltage generator 58 and the voltage applied to the electrode line 15 will be described later.

  The drive signal generator 57 generates an analog voltage signal based on waveform data relating to the waveform of the drive signal. The drive signal generator 57 amplifies the voltage signal to generate the drive signal COM. This drive signal COM is applied to the piezoelectric vibrator 20 which is a pressure generating means of the recording head 2 during a recording operation or a flushing operation on the recording paper 6, and within a unit period which is a repetitive cycle, for example, FIG. 6 is a series of signals including at least one injection driving pulse DP shown in FIG. Here, the ejection drive pulse DP is for causing the piezoelectric vibrator 20 to perform a predetermined operation in order to eject ink droplets from the nozzles 30 of the recording head 2.

  FIG. 6 is a waveform diagram showing an example of the configuration of the ejection drive pulse DP included in the drive signal COM. In FIG. 6, the vertical axis represents potential and the horizontal axis represents time. Further, as shown in FIG. 6, the ejection drive pulse DP of the present embodiment has a positive polarity on average. The ejection drive pulse DP has an expansion element p1 that expands the pressure chamber 28 by changing the potential from the reference potential (intermediate potential) Vb to the maximum potential (maximum voltage) Vmax and expands to maintain the maximum potential Vmax for a certain period of time. The maintenance element p2, the contraction element p3 that rapidly contracts the pressure chamber 28 by changing the potential from the maximum potential Vmax to the minimum potential (minimum voltage) Vmin, and the contraction maintenance (control) that maintains the minimum potential Vmin for a certain period of time. Oscillation hold) element p4 and a return element p5 for returning the potential from the minimum potential Vmin to the reference potential Vb.

  When the ejection drive pulse DP is applied to the piezoelectric vibrator 20, it operates as follows. First, the piezoelectric vibrator 20 is contracted by the expansion element p1, and the pressure chamber 28 is expanded from the reference volume corresponding to the reference potential Vb to the maximum volume corresponding to the maximum potential Vmax. Thereby, the meniscus exposed to the nozzle 30 is drawn into the pressure chamber 28 side. The expansion state of the pressure chamber 28 is maintained constant throughout the application period of the expansion maintaining element p2. When the contraction element p3 is applied to the piezoelectric vibrator 20 subsequent to the expansion maintaining element p2, the piezoelectric vibrator 20 expands, whereby the pressure chamber 28 has a minimum volume corresponding to the minimum potential Vmin from the maximum volume. Shrinks rapidly until The ink in the pressure chamber 28 is pressurized by the rapid contraction of the pressure chamber 28, and thereby, several pl to several tens pl of ink is ejected from the nozzle 30. The contraction state of the pressure chamber 28 is maintained for a short time over the application period of the contraction maintaining element p4, and then the damping element p5 is applied to the piezoelectric vibrator 20 so that the pressure chamber 28 corresponds to the minimum potential Vmin. The volume returns to the reference volume corresponding to the reference potential Vb.

  Next, the flushing operation and the collection of mist that occurs with this will be described. The flushing operation of the present embodiment is operated by a series of signals including at least one ejection drive pulse DP, and ejects ink at least once during the flushing operation period Tf. The flushing operation is performed when the recording operation has not been performed for a long period of time, or when the ink cartridge is replaced, etc., and discharges thickened ink or bubbles mixed in the ink. To do.

  The ink ejected from the nozzles 30 by the flushing operation is stretched during the flight, for example, the leading main droplet (main droplet), the minute satellite droplet generated after that, and further, Separate into fine mists. Here, as described above, in the flushing operation period Tf, since the voltage generation unit 58 is in an off state, an electric field is not formed between the electrode line 15 and the nozzle formation surface. For this reason, these droplets are not charged by electrostatic induction due to an electric field between the electrode wire 15 and the nozzle forming surface. However, these droplets are charged by the Leonard effect. That is, the droplets are positively charged due to evaporation and splitting of the surface layer portion during flight. Among these droplets, satellite droplets and mists smaller than these droplets (hereinafter referred to as mists Ms) float on the flushing box 13 without landing.

  These floating mists Ms are collected by the electrode wire 15 after the flushing operation. Specifically, as shown in FIG. 7A, when the voltage generating unit 58 is switched on after the flushing operation is completed, an electric field is generated between the electrode line 15 and the nozzle formation surface of the recording head 2. Is formed. In the present embodiment, since a negative voltage is applied to the electrode wire 15, a positively charged mist or the like Ms is attracted to and attracted to the electrode wire 15. Even when the recording head 2 has moved to a position off the upper side of the flushing box 13, as shown in FIG. 7B, in addition to the electrode line 15 and the nozzle forming surface of the recording head 2 that has moved, the printer An electric field is formed between the members constituting 1 and the flushing box 13. Therefore, the positively charged mist or the like Ms is attracted to the electrode wire 15 to which a negative voltage is applied. Thereby, it can reduce that these mists Ms adhere to other components (for example, a motor, a drive belt, a linear scale, etc.) in an apparatus.

  Note that the force with which the mist Ms is attracted to the electrode wire 15 is determined by the product of the charge amount of the mist Ms and the electric field strength formed by the electrode wire 15. The amount of charge of Ms such as mist due to the Leonard effect is determined by the conductivity of Ms (ink) such as mist and the flight time (dwell time) of Ms such as mist. For this reason, the strength of the voltage applied to the electrode line 15 and the voltage application time depend on the conductivity of the ink used and the distance between the nozzle formation surface of the recording head 2 and the bottom surface (electrode line 15) in the flushing box 13. It can be determined by d (see FIG. 7A).

  FIG. 8 is a graph showing the relationship between the conductivity of the ink droplet (droplet) and the charge amount of the ink droplet due to the Leonard effect. In this graph, the amount of charge after an ink droplet that was not initially charged flies for a certain period of time is measured and plotted for each ink droplet having a different conductivity. The horizontal axis of the graph represents the ink droplet conductivity (mS / cm), and the vertical axis represents the ink droplet charge amount (C). As can be seen from the graph, when the conductivity of the ink droplet is about 10 (mS / cm) or less, the charge amount of the ink droplet tends to increase. That is, it can be seen that it is desirable to use an ink having a conductivity of about 10 (mS / cm) or less in order to more securely adsorb Ms such as mist to the electrode wire 15. FIG. 9 is a graph showing the relationship between the distance between the nozzle formation surface (nozzle 30) of the recording head 2 and the landing target (electrode line 15) and the charge amount due to the Leonard effect of the flying ink droplets. In this graph, the amount of charge when an ink droplet that was not initially charged landed on the landing target was measured and plotted by changing the distance from the nozzle formation surface to the landing target, and the conductivity was 30. (ΜS / cm) (◯ in FIG. 9), 1 (mS / cm) (Δ in FIG. 9), and 12 (mS / cm) (□ in FIG. 9) represent the values measured for each ink. . The ink droplet ejection speed is constant. In addition, the horizontal axis of the graph represents the distance (mm) from ejection of the ink droplet to the landing target, that is, the flight time (flying time), and the vertical axis represents the charge amount (C) of the ink droplet. According to this graph, it can be seen that the charge amount of the ink droplet tends to increase as the dwell time of the ink droplet increases. It can also be seen that the tendency is stronger as the conductivity of the ink droplet is smaller. Thus, if the conductivity of the ink and the distance d between the nozzle formation surface of the recording head 2 and the electrode line 15 are determined, the charge amount of Ms such as mist can be obtained.

The force applied to Ms such as mist is determined by the product of the amount of charge of Ms such as mist and the strength of the electric field. FIG. 10 is a graph showing the relationship between the strength of the electric field formed by the electrode wires 15 and the recovery rate of the droplets (Mist or the like Ms). In this graph, the recovery rate of droplets to the landing target is measured and plotted by changing the strength of the voltage applied to the landing target (electrode line 15), and the end of the droplet (when landing) ) Is 2.3 × 10 ⁻¹⁷ (C) (◯ in FIG. 10), 1.2 × 10 ⁻¹⁶ (C) (Δ in FIG. 10), 3 × 10 ⁻¹⁶ (C) (FIG. 10 □), 5 × 10 ⁻¹⁶ (C) (× in FIG. 10), the values measured in each case are shown. For example, when the charge amount at the end of the droplet is 2.3 × 10 ⁻¹⁷ (C) (substantially the same charge amount as when the ink conductivity is about 10 (mS / cm) or less), If an electric field of at least about 160 (V / mm) is formed between the electrode lines 15, almost 100 (%) of droplets can be collected. Therefore, a voltage may be applied to the electrode line 15 so that an electric field of at least 160 (V / mm) is formed between the nozzle formation surface of the recording head 2 and the electrode line 15. Thus, if the charge amount of Ms such as mist is known, the voltage applied to the electrode wire 15 can be determined. Here, since the charge amount of Ms such as mist can be obtained from the ink conductivity and the distance d between the nozzle formation surface of the recording head 2 and the electrode line 15 as described above, these set values are determined. For example, the voltage applied to the electrode wire 15 can be determined.

  By the way, the speed at which the ink droplet moves is determined by the mass of the ink droplet, the initial velocity when ejected from the nozzle, the strength of the electric field, and the like. Depends on the size. Here, it has been confirmed that the speed of Ms such as mist when an electric field capable of collecting almost 100% of droplets is applied is 1 (m / s) or more at the lowest. For this reason, if the distance between the nozzle forming surface and the electrode wire 15 is d (m), the mist or the like Ms can be obtained if the time Te (see FIG. 5) for applying a voltage to the electrode wire 15 is at least d (s). It is possible to reliably collect.

  As described above, since the voltage is applied to the electrode line 15 after the flushing operation for ejecting the liquid from the recording head 2 toward the flushing box 13, the voltage is not applied to the electrode line 15 during the flushing operation, and mist or the like is applied. Ms can be prevented from being charged to the same polarity as the electrode wire 15 by electrostatic induction, and by applying a voltage to the electrode wire 15 after the flushing operation is completed, Ms such as mist can be collected on the electrode wire 15. It becomes possible. Thereby, it is reduced that these mists Ms adhere to the other component in an apparatus. As a result, failure due to adhesion of Ms such as mist is suppressed, and durability and reliability of the printer 1 are improved. In addition, since a negative voltage is applied to the electrode wire 15, Ms such as mist can be collected on the electrode wire 15 when the mist is charged positively (plus) due to the Leonard effect.

  By the way, the flushing operation is not limited to the above-described embodiment. For example, the flushing operation in the second embodiment shown in FIG. 11 is configured to have two short-term flushing operations by dividing the period during which flushing is performed. Then, after the previous short-term flushing operation period Tf1, before the next short-term flushing operation period Tf2 and after the short-term flushing operation period Tf2 (flushing operation period Tf), the voltage generator 58 applies a voltage to the electrode line 15. doing. Each short-term flushing operation is performed by a series of signals including at least one ejection drive pulse DP, and ink is ejected at least once during each short-term flushing operation Tf1 and Tf2. In this embodiment, the period Te2 in which the voltage is applied to the electrode line 15 after the end of the flushing operation period Tf is longer than the period Te1 in which the voltage is applied to the electrode line 15 between the short-term flushing operations Tf1 and Tf2. Is set. As described above, it is desirable that the voltage application period Te1 be d (s) or longer, but at least the voltage application period Te2 only needs to be d (s) or longer. Furthermore, since other configurations are the same as those of the printer 1 of the first embodiment, description thereof is omitted.

  Thus, in this embodiment, by applying a voltage to an electrode part every time short-term flushing operation is completed, scattering of mist can be prevented and mist can be collected on the electrode part more reliably. Note that the number of short-term flushing operations within the flushing operation period Tf is not limited to two, and a configuration having two or more short-term flushing operations within the flushing operation period Tf may be employed. In this case, a voltage may be applied to the electrode line 15 after at least one short-term flushing operation and before the next short-term flushing operation.

  Further, the voltage application unit to which the voltage is applied by the voltage generation unit 58 is not limited to the electrode wire 15 described above. In the third embodiment shown in FIG. 12, a metal plate is formed above the ink absorbing material 14 disposed on the bottom surface of the flushing box 13 (on the recording head 2 side) and inside the side wall of the flushing box 13. An electrode plate 61 is annularly arranged along the side wall. The electrode plate 61 is used as a voltage application unit, and a voltage generation unit 58 is connected to the electrode plate 61. If comprised in this way, since the area of the electrode plate 61, ie, the area which touches air | atmosphere, can be set larger than the case of a wire, Ms etc. can be collected in a wide range and collection efficiency of Ms etc. is improved. be able to. Since other configurations are the same as those of the printer 1 of the first embodiment, the description thereof is omitted.

  Furthermore, in the fourth embodiment shown in FIG. 13, the ink absorbing material 14 'disposed on the bottom surface of the flushing box 13 is formed of a porous member having liquid absorbency made of a metal sponge or the like. Thus, a voltage applied portion is obtained. That is, the voltage generator 58 is connected to the ink absorbing material 14 'so that a voltage can be applied to the ink absorbing material 14'. In this case, Ms such as mist can be directly collected in the ink absorbing material 14 '. Since other configurations and effects are the same as those of the printer 1 of the first embodiment, the description thereof is omitted.

  In each of the above embodiments, the flushing operation is configured to move the recording head onto the flushing box and eject the liquid from the nozzle toward the flushing box. However, the present invention is not limited to this. For example, the nozzle forming surface of the recording head is sealed with a capping member, and in this state, a flushing operation can be performed in which ink is ejected from the nozzle toward the capping member. In this case, the same configuration as the voltage application unit in the flushing box exemplified in each of the above embodiments may be employed for the capping member that is the droplet collecting means. Thereby, it can prevent that mist etc. adhere to a nozzle formation surface. Further, when the recording head moves to the platen side after the flushing operation to perform the recording operation, it is possible to suppress mist and the like from being scattered by the air flow generated with the movement of the recording head.

  Further, the drive pulse for driving the piezoelectric vibrator used for the flushing operation is not limited to the ejection drive pulse DP shown in FIG. The waveform of the drive pulse can be changed according to the degree of ink thickening. In short, any waveform may be used as long as ink droplets can be ejected from the nozzle toward the flushing box.

  Further, the present invention is not limited to a printer as long as it is a liquid ejecting apparatus capable of controlling the ejection of liquid using a pressure generating means, and various ink jet recording apparatuses and recording apparatuses such as a plotter, a facsimile machine, a copier, etc. The present invention can also be applied to other liquid ejecting apparatuses such as a display manufacturing apparatus, an electrode manufacturing apparatus, and a chip manufacturing apparatus. In the display manufacturing apparatus, a solution of each color material of R (Red), G (Green), and B (Blue) is ejected from the color material ejecting head. Moreover, in an electrode manufacturing apparatus, a liquid electrode material is ejected from an electrode material ejection head. In the chip manufacturing apparatus, a bioorganic solution is ejected from a bioorganic ejecting head.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 5 ... Platen, 6 ... Recording paper, 11 ... Capping member, 13 ... Flushing box, 14 ... Ink absorber, 15 ... Electrode wire, 20 ... Piezoelectric vibrator, 24 ... Nozzle plate, 30 ... Nozzle, 58 ... Voltage generator, 61 ... Electrode plate

Claims (7)

A nozzle forming surface on which nozzles for ejecting liquid are formed, and pressure generating means that is driven by application of a drive signal to cause pressure fluctuations in the liquid in the pressure chamber that communicates with the nozzles. A liquid ejecting head that ejects liquid from the nozzle toward the landing target by driving;
A support unit that is disposed at an interval with respect to the nozzle formation surface of the liquid jet head when performing the jetting operation, and supports the landing target;
Droplet collecting means disposed at a position outside the ejection region in the support means for ejecting liquid from the liquid ejecting head to the landing target;
A voltage applied portion provided in the droplet collecting means;
Voltage applying means for applying a voltage to the voltage applied portion;
With
The liquid ejecting apparatus, wherein the voltage applying unit applies a voltage to the voltage application unit after a flushing operation of ejecting the liquid from the liquid ejecting head toward the droplet collecting unit. The flushing operation includes at least two short-term flushing operations;
2. The liquid ejecting apparatus according to claim 1, wherein the voltage applying unit applies a voltage to the voltage application unit after one short-term flushing operation and before the next short-term flushing operation.   The liquid ejecting apparatus according to claim 1, wherein the voltage applying unit applies a negative voltage to the voltage application unit.   The liquid ejecting apparatus according to claim 3, wherein the conductivity of the liquid is 10 (mS / cm) or less.   5. The liquid ejecting apparatus according to claim 3, wherein an electric field strength from the voltage application portion toward the nozzle formation surface is 160 (V / mm) or more. A nozzle forming surface on which nozzles for ejecting liquid are formed, and pressure generating means that is driven by application of a drive signal to cause pressure fluctuations in the liquid in the pressure chamber that communicates with the nozzles. A liquid ejecting head that ejects liquid from the nozzle toward the landing target by driving;
A support unit that is disposed at an interval with respect to the nozzle formation surface of the liquid jet head when performing the jetting operation, and supports the landing target;
Droplet collecting means disposed at a position outside the ejection region in the support means for ejecting liquid from the liquid ejecting head to the landing target;
A voltage applied portion provided in the droplet collecting means;
Voltage applying means for applying a voltage to the voltage applied portion;
A liquid ejecting apparatus control method comprising:
A control method of a liquid ejecting apparatus, wherein the voltage applying means applies a voltage to the voltage application portion after a flushing operation for ejecting liquid from the liquid ejecting head toward the droplet collecting means. The flushing operation includes at least two short-term flushing operations;
5. The method of controlling a liquid ejecting apparatus according to claim 4, wherein the voltage applying unit applies a voltage to the voltage application portion after one short-term flushing operation and before the next short-term flushing operation. .

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