JP2019130726A - Liquid discharge device and control method for liquid discharge device - Google Patents

Abstract

To provide a liquid discharge device which enhances discharge efficiency in cleaning operation and can reduce an amount of consumption of liquid, and a control method for the liquid discharge device.SOLUTION: A liquid discharge device comprises: a liquid discharge head (10) individually having a plurality of nozzles (30) discharging liquid, a plurality of pressure chambers (33) communicating with the nozzles and a plurality of driving elements (31) causing pressure fluctuation of the liquid in the pressure chambers, and having a common liquid chamber (43) with which the plurality of pressure chambers commonly communicates; a cleaning mechanism individually causing the liquid to be discharged from the plurality of nozzles; and a drive waveform generation circuit (19) generating a drive waveform (Pa) driving at least a part of the driving elements out of the plurality of driving elements when discharging the liquid from the plurality of nozzles by the cleaning mechanism.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a liquid ejection apparatus that performs a cleaning operation for discharging liquid from a plurality of nozzles, and a method for controlling the liquid ejection apparatus.

  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 is an image recording device such as an ink jet printer or an ink jet plotter. 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 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.

  This type of liquid discharge head includes a liquid flow path from a liquid storage member that stores liquid to a nozzle through a common liquid chamber (also referred to as a reservoir or a manifold) and a pressure chamber via a liquid introduction port. By driving a driving element (actuator) such as an element or a heating element, a pressure fluctuation is generated in the liquid in the nozzle or the pressure chamber, and the liquid is discharged from the nozzle by using the pressure fluctuation. The liquid discharge head includes a plurality of nozzles, the liquid is supplied from the liquid storage member to the common liquid chamber through the liquid supply path, and the liquid is distributed and supplied from the common liquid chamber to the nozzles.

  The common liquid chamber has a large area (or volume) compared to other flow paths in the liquid discharge head because a large number of nozzles communicate with each other. For this reason, the liquid between the nozzle communicating with the common liquid chamber relatively near the liquid inlet for introducing the liquid into the common liquid chamber and the nozzle communicating with the common liquid chamber at a position farther from the liquid inlet. In order to make the supply pressure as uniform as possible, the common liquid chamber having a tapered structure in which the inner wall surface at the end of the common liquid chamber is inclined so as to spread from the liquid inlet side toward the communication side with the nozzle. This type of liquid discharge head is used (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 06-091874

  However, even in the common liquid chamber in which such a tapered structure is adopted, the liquid tends to stagnate at a position away from the liquid introduction port as compared with a position near the liquid introduction port. For this reason, when performing a cleaning operation for forcibly discharging the liquid from each nozzle, the pressure at the nozzle far from the liquid inlet is higher than that at the nozzle near the liquid inlet. The pressure applied to the liquid is difficult to act, and the discharge efficiency of the liquid and bubbles is low. In such a configuration, the strength in the cleaning operation (pressure applied to the liquid in the flow path, the cleaning operation time, etc.) in order to obtain a sufficient liquid discharge amount in each nozzle including the nozzle separated from the liquid introduction port. When raised as a whole, the liquid is discharged more than necessary at the nozzle close to the liquid inlet. As a result, there is a problem that the amount of liquid consumed in the cleaning operation increases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid ejecting apparatus capable of increasing discharge efficiency in a cleaning operation and reducing liquid consumption, and a liquid ejecting apparatus. A control method is provided.

The liquid ejection apparatus of the present invention has been proposed to achieve the above object, and is a nozzle that ejects liquid, a pressure chamber that communicates with the nozzle, and a drive that causes pressure fluctuations in the liquid in the pressure chamber. A liquid discharge head having a plurality of elements and a common liquid chamber in which the plurality of pressure chambers communicate in common;
A cleaning mechanism for discharging liquid from each of the plurality of nozzles;
A drive waveform generation circuit that generates a drive waveform for driving at least some of the plurality of drive elements when the liquid is discharged from the plurality of nozzles by the cleaning mechanism;
It is characterized by providing.

  According to the present invention, when performing the cleaning operation for discharging the liquid from the plurality of nozzles by the cleaning mechanism, at least a part of the plurality of driving elements is driven to move the common liquid chamber to the specific nozzle. A pressure change that promotes or prevents the inflow of liquid can be generated in the pressure chamber corresponding to the specific nozzle. This makes it possible to increase the discharge efficiency of liquids and bubbles even in nozzles where the pressure during the cleaning operation is less likely to act than other nozzles. For this reason, it is possible to reduce the amount of liquid consumed in the cleaning operation.

In the above configuration, the liquid discharge head includes a liquid introduction port for introducing liquid into the common liquid chamber,
The nozzle includes a first nozzle having a liquid path length from the liquid inlet to the nozzle having a predetermined value or more, and a second nozzle having a liquid path length less than the predetermined value. ,
A configuration in which at least one of the drive elements corresponding to the first nozzle and the drive elements corresponding to the second nozzle is the partial drive element may be employed.

  According to this configuration, at the time of performing the cleaning operation, by driving at least one of the first nozzle driving element and the second nozzle driving element, it is possible to promote the inflow of liquid from the common liquid chamber to the first nozzle. . As a result, it is possible to increase the discharge efficiency of the liquid and bubbles even in the first nozzle where the pressure during the cleaning operation is less likely to act than the second nozzle because the length of the liquid path is equal to or greater than the predetermined value. .

In the above configuration, the liquid inlet is located at a central portion in the first direction of the common liquid chamber,
The first nozzle communicates with an end of the common liquid chamber in the first direction;
It is desirable that the second nozzle adopt a configuration communicating with the central portion of the common liquid chamber.

  According to this configuration, it is possible to increase the discharge efficiency of the liquid and bubbles even in the first nozzle communicating with the end of the common liquid chamber where the flow tends to stagnate.

  In the above-described configuration, it is preferable that the drive waveform applied to the drive element corresponding to the first nozzle is a first drive waveform that swings the meniscus in the first nozzle toward the discharge side.

  According to this configuration, it is possible to promote the inflow of liquid from the common liquid chamber to the first nozzle by swinging the meniscus in the first nozzle toward the discharge side, so that the discharge efficiency of liquid and bubbles in the first nozzle is increased. It becomes possible.

In the above-described configuration, it is preferable that the drive waveform applied to the drive element corresponding to the second nozzle is a second drive waveform that swings the meniscus in the second nozzle toward the pressure chamber. .

  According to this configuration, it is possible to increase the liquid and bubble discharge efficiency in the first nozzle by inhibiting the inflow of the liquid into the second nozzle by swinging the meniscus in the second nozzle to the pressure side. Become.

The control method of the liquid ejection apparatus of the present invention includes a plurality of nozzles that eject liquid, a pressure chamber that communicates with the nozzle, and a plurality of drive elements that cause pressure fluctuations in the liquid in the pressure chamber. A liquid discharge head having a common liquid chamber that communicates in common with each other, a cleaning mechanism that discharges liquid from each of the plurality of nozzles, and a drive waveform generation circuit that generates a drive waveform that drives the drive element, A method for controlling a liquid ejection apparatus comprising:
When the liquid is discharged from the plurality of nozzles by the cleaning mechanism, at least some of the plurality of driving elements are driven by the driving waveform.

It is a front view explaining the structure of one form of a liquid discharge apparatus (printer). It is a block diagram explaining the electrical structure of a liquid discharge apparatus. FIG. 3 is a cross-sectional view of an embodiment of a liquid discharge head (recording head). FIG. 4 is an enlarged view of a region X in FIG. 3. It is a top view of a communicating plate. It is a flowchart explaining the flow of a process of cleaning operation. It is a schematic diagram explaining the pressure which acts on each nozzle in the conventional cleaning operation | movement. It is a wave form diagram of an example of an assist drive pulse. It is a schematic diagram explaining the pressure which acts on each nozzle in the cleaning operation which concerns on 1st Embodiment. It is a schematic diagram explaining the pressure which acts on each nozzle in the cleaning operation | movement which concerns on 2nd Embodiment. It is a wave form diagram of the modification of an assist drive pulse. It is a schematic diagram explaining the pressure which acts on each nozzle in the cleaning operation which concerns on 3rd Embodiment. It is a wave form diagram of an example of an interrupt drive pulse. It is a schematic diagram explaining the pressure which acts on each nozzle in the cleaning operation which concerns on 4th Embodiment. It is a schematic diagram explaining the pressure which acts on each nozzle in the cleaning operation which concerns on 5th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. Note that, 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 this embodiment. 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 a configuration of a printer 1 including a recording head 10 which is a kind of liquid ejection head. FIG. 2 is a block diagram illustrating the electrical configuration of the printer 1. The printer 1 according to the present embodiment includes a frame 2 and a platen 3 disposed in the frame 2, and a recording sheet, a fabric, or a sheet on the platen 3 by a transport mechanism 4 (see FIG. 2). A medium such as a resin sheet (a kind of liquid landing target) is conveyed. A guide rod 5 is installed in the frame 2 in parallel with the platen 3, and a carriage 6 on which a recording head 10 is mounted is slidably supported on the guide rod 5. The carriage 6 is configured to reciprocate in the main scanning direction orthogonal to the medium transport direction along the guide rod 5 by driving the carriage moving mechanism 7 (see FIG. 2). The printer 1 ejects ink (a kind of liquid in the present invention) from the nozzles 30 (see FIG. 3 and the like) of the recording head 10 while moving the carriage 6 relative to the medium on the platen 3 in the main scanning direction. Then, landing patterns such as characters and images are formed (recorded / printed) by landing the ink on the medium.

  An ink cartridge 8 (a type of liquid storage member) that stores ink is detachably mounted on the carriage 6. Examples of the ink include water-based dye ink or pigment ink, organic solvent-based (ecosolvent-based) ink having higher weather resistance than these water-based inks, and photo-curable ink that is cured by irradiation with ultraviolet rays. Well-known various compositions can be used. In the present embodiment, the configuration in which the ink cartridge 8 is mounted on the carriage 6 is illustrated. However, the present invention is not limited to this, and the ink cartridge 8 is disposed on the main body side of the printer 1 and is recorded via the ink supply tube. It is also possible to employ a configuration supplied to the head 10.

  In a region outside the platen 3 in the frame 2, a wiping mechanism 11 for wiping a nozzle forming surface (a surface facing the platen 3, see FIG. 3) of the nozzle plate 24 of the recording head 10 mounted on the carriage 6. Is arranged. The wiping mechanism 11 has a wiper 12. The wiper 12 is made of an elastic / flexible member such as rubber or elastomer. The wiping mechanism 11 arranges the wiper 12 at a position where the tip of the wiper 12 can contact the nozzle forming surface of the recording head 10 in the wiping operation. Then, the nozzle forming surface is wiped by the wiper 12 by relatively moving the wiper 12 in a state where the tip of the wiper 12 is in contact with the nozzle forming surface.

  A capping mechanism 13 (a kind of cleaning mechanism in the present invention) is disposed adjacent to the wiping mechanism 11 at a home position that is a standby position of the carriage 8 in the frame 2. The capping mechanism 13 has a cap 14 (a kind of sealing member) made of a tray-like elastic member that can come into contact with the nozzle forming surface of the recording head 10. The capping mechanism 13 is configured such that the space in the cap 14 functions as a sealing space, and can be brought into close contact with the nozzle forming surface with the nozzle 30 of the recording head 10 facing the sealing space. Further, a pump unit 16 (see FIG. 2) is connected to the cap 14 via a waste liquid tube (not shown), and the operation of the pump unit 16 causes the inside of the sealed space of the cap 14 to be negatively charged via the waste liquid tube. Can be compressed. In the cleaning operation for eliminating the clogging of the nozzles 30 and the ink flow paths of the recording head 10, the sealed space (sealed space) is negatively pressured while being in close contact with the nozzle forming surface, and recording is performed from the nozzles 30. Ink and bubbles in the head 10 are sucked and discharged into the sealed space of the cap 14.

  As shown in FIG. 2, the printer 1 in this embodiment includes a CPU 17, a storage device 18, a drive signal generation circuit 19 (a type of drive waveform generation circuit), an input / output interface 20, a transport mechanism 4, a carriage movement mechanism 7, A wiping mechanism 11, a capping mechanism 13, a pump unit 16, and a recording head 10 are included. The input / output interface 20 receives a request for a printing operation from the external device side, print setting information, print data (image data), etc., outputs the status information of the printer 1 to the external device, and transmits and receives various data. . The CPU 17 is an arithmetic processing unit for controlling the entire printer, and controls a printing operation (liquid ejection operation) and the like by the recording head 10. The storage device 18 is an element that stores a program for the CPU 17 and data used for various controls, and includes a ROM, a RAM, and an NVRAM (nonvolatile storage element). The drive signal generation circuit 19 generates a drive signal including a drive waveform (described later) for driving the piezoelectric element 31 of the recording head 10 based on waveform data relating to the waveform of the drive signal.

Next, the configuration of the recording head 10 in the present embodiment will be described.
3 is a cross-sectional view of the recording head 10, and FIG. 4 is an enlarged view of a region X in FIG. The recording head 10 according to the present embodiment is a unit in which a plurality of head components such as a fixed plate 23, a nozzle plate 24, a communication plate 25, an actuator unit 26, a compliance substrate 27, and a holder 28 are stacked and bonded together with an adhesive or the like. It has become. In the following description, the stacking direction of the constituent members of the recording head 10 will be described as the vertical direction as appropriate.

  The actuator unit 26 in this embodiment includes a pressure chamber forming substrate 29 in which a plurality of pressure chambers 33 communicating with a plurality of nozzles 30 formed in the nozzle plate 24 are formed, and pressure fluctuations in the ink in each pressure chamber 33. A plurality of piezoelectric elements 31 as drive elements for generating the pressure chamber, a pressure chamber forming substrate 29 and a protective substrate 32 for protecting the piezoelectric elements 31 are provided in a stacked state. A wiring empty portion 40 through which the flexible substrate 39 on which the drive IC 38 is mounted is opened at a substantially central portion in plan view of the protective substrate 32. A lead electrode of the piezoelectric element 31 is disposed in the wiring space 40, and a wiring terminal of the flexible substrate 39 is electrically connected to the lead electrode. A drive signal sent from the drive signal generation circuit 19 is supplied to the piezoelectric element 31 through the flexible substrate 39. The flexible substrate 39 is not limited to the one provided with the drive IC 38, and a configuration in which the drive IC 38 is separately disposed on the protective substrate 32 via a so-called interposer may be employed.

  The pressure chamber forming substrate 29 of the actuator unit 26 is made of a silicon single crystal substrate. The pressure chamber forming substrate 29 is provided with a plurality of liquid chambers corresponding to the nozzles 30 as the pressure chambers 33. The pressure chamber 33 is a hollow portion that is long in a direction intersecting with the nozzle row (orthogonal in the present embodiment). A nozzle communication port 34 communicates with one end of the pressure chamber 33 in the longitudinal direction, and an individual communication port 35 communicates with the other end. Two rows of pressure chambers 33 are formed on the pressure chamber forming substrate 29 in the present embodiment.

A vibration plate 36 is laminated on the upper surface of the pressure chamber forming substrate 29 (the surface opposite to the communication plate 25 side), and the upper opening of the pressure chamber 33 is sealed by the vibration plate 36. The vibration plate 36 includes, for example, an elastic film made of silicon dioxide (SiO ₂ ) formed on the upper surface of the pressure chamber forming substrate 29 and an insulator film made of zirconium oxide (ZrO ₂ ) formed on the elastic film. And consist of And the piezoelectric element 31 is laminated | stacked on the area | region corresponding to each pressure chamber 33 on this diaphragm 36, respectively.

  The piezoelectric element 31 of the present embodiment is a so-called bending mode piezoelectric element. The piezoelectric element 31 is formed, for example, by sequentially laminating a lower electrode layer, a piezoelectric layer, and an upper electrode layer (all not shown) on the vibration plate 36. The piezoelectric element 31 configured in this manner bends and deforms in the vertical direction when an electric field corresponding to the potential difference between both electrodes is applied between the lower electrode layer and the upper electrode layer. In the present embodiment, two rows of piezoelectric elements 31 are formed corresponding to the rows of pressure chambers 33 formed in two rows. The lower electrode layer and the upper electrode layer extend as lead electrodes from the rows of the piezoelectric elements 31 on both sides to the inside of the wiring space 40 between the rows, and are electrically connected to the flexible substrate 39 as described above. ing.

  The protective substrate 32 is laminated on the vibration plate 36 so as to cover the rows of the piezoelectric elements 31 formed in two rows. Inside the protective substrate 32, a long accommodation space 41 that can accommodate the rows of piezoelectric elements 31 is formed. The accommodation space 41 is a recess formed partway in the height direction of the protective substrate 32 from the lower surface side (the diaphragm 36 side) of the protective substrate 32 toward the upper surface side (the holder 28 side). In the protection substrate 32 in the present embodiment, accommodation spaces 41 are respectively formed on both sides of the wiring vacant portion 40. A communication plate 25 having a larger area than the actuator unit 26 is joined to the lower surface of the actuator unit 26.

FIG. 5 is a plan view of the communication plate 25.
The communication plate 25 in the present embodiment is made of a silicon single crystal substrate in the same manner as the pressure chamber forming substrate 29. In the communication plate 25 in the present embodiment, a nozzle communication port 34 for communicating the pressure chamber 33 and the nozzle 30, a reservoir 43 (a kind of common liquid chamber, also referred to as a manifold) provided in common to each pressure chamber, and The individual communication port 35 communicating the reservoir 43 and the pressure chamber 33 is formed by, for example, anisotropic etching. The reservoirs 43 in this embodiment are liquid chambers extending along the nozzle row direction, and two reservoirs 43 are formed corresponding to each nozzle row of the nozzle plate 24 in the communication plate 25 in this embodiment. The opening on the lower surface side of the reservoir 43 (the side opposite to the pressure chamber forming substrate 29 side) is sealed with the compliance sheet 44 of the compliance substrate 27. It is also possible to employ a configuration in which a plurality of reservoirs are provided for one nozzle row, and different types of ink are assigned to the respective reservoirs. The nozzle communication port 34, the individual communication port 35, and the reservoir 43 are formed by anisotropic etching from the lower surface side of the communication plate 25. As will be described later, ink is introduced into the reservoir 43 through an ink introduction port 52 (a kind of liquid introduction port in the present invention) of an introduction liquid chamber 51 provided in the holder 28. A plurality of individual communication ports 35 are formed along the nozzle row direction corresponding to the respective pressure chambers 33. The individual communication port 35 communicates with the end portion on the other side in the longitudinal direction of the pressure chamber 33 (the side opposite to the side communicating with the nozzle communication port 34).

  The reservoir 43 in this embodiment includes a first reservoir 43a that communicates with the introduction liquid chamber 51 of the holder 28, a second reservoir 43b that communicates the first reservoir 43a and the individual communication port 35, Consists of The first reservoir portion 43 a is an empty portion having an opening having a shape and a dimension that follows the opening shape of the bottom surface side of the introduction liquid chamber 51 of the holder 28, and is a portion that penetrates the thickness direction of the communication plate 25. In the present embodiment, the ink introduction port 52 of the holder 28 is located at a position corresponding to the longitudinal direction of the first reservoir 43a, that is, the central portion in the nozzle row direction (corresponding to the first direction in the present invention). ing. The second reservoir portion 43b is a portion that is recessed from the lower surface side to the middle of the plate thickness direction, leaving the thin portion 43c on the upper surface side of the communication plate 25, and intersects the first reservoir portion 43a in the nozzle row direction. It is formed adjacent to the direction (second direction orthogonal in the present embodiment). The second reservoir portion 43b extends along the first reservoir portion 43a from one end of the first reservoir portion 43a to the other end in the nozzle row direction. One end of the second reservoir 43b in the direction intersecting the nozzle row direction communicates with the first reservoir 43a, while the other end of the second reservoir 43b is joined to the communication plate 25. It is formed so as to communicate with individual communication ports 35 communicating with 29 pressure chambers 33. In the present embodiment, among the inner wall surfaces defining the first reservoir portion 43a, the wall surfaces respectively positioned at both ends in the nozzle row direction are on the individual communication port 35 side in the direction orthogonal to the nozzle row direction (second The tapered surface 42 is inclined so that the liquid chamber expands from the opposite side to the individual communication port 35 side. That is, in the nozzle row direction, both ends of the reservoir 43 are configured such that the flow path becomes narrower toward the respective ends.

  A nozzle plate 24 in which a plurality of nozzles 30 are formed is joined to a substantially central portion of the lower surface of the communication plate 25. The nozzle plate 24 in the present embodiment is a plate material having an outer shape smaller than that of the communication plate 25 and the actuator unit 26, and is made of, for example, a metal plate such as stainless steel or a silicon single crystal substrate. The nozzle plate 24 is located at a position deviated from the opening of the reservoir 43 on the lower surface of the communication plate 25, and the nozzle communication port 34 and the plurality of nozzles 30 communicate with each other in a region where the nozzle communication port 34 is opened. In such a state, it is joined with an adhesive or the like. The nozzle plate 24 in the present embodiment is formed with a total of two nozzle rows in which a plurality of nozzles 30 are arranged. In the present embodiment, one nozzle row (nozzle group) is composed of, for example, 400 nozzles 30. The nozzle group is not limited to one in which a plurality of nozzles are arranged in a line, and one in which a plurality of nozzles are arranged in a matrix can also be employed. In short, the nozzle group may be composed of a plurality of nozzles to which liquids are respectively supplied from the same reservoir (common liquid chamber).

  In addition, a compliance substrate 27 is bonded to the lower surface of the communication plate 25 at a position away from the nozzle plate 24. The compliance substrate 27 is positioned and joined to the lower surface of the communication plate 25 and seals the opening of the reservoir 43 on the lower surface of the communication plate 25. As shown in FIG. 4, the compliance substrate 27 in the present embodiment is configured by joining a compliance sheet 44 (a kind of compliance member) and a support plate 45 that supports the compliance sheet 44. The compliance sheet 44 of the compliance substrate 27 is bonded to the lower surface of the communication plate 25 so that the compliance sheet 44 is sandwiched between the communication plate 25 and the support plate 45. The compliance sheet 44 is made of a flexible thin film, for example, a synthetic resin material such as polyphenylene sulfide (PPS). The support plate 45 is formed of a metal material such as stainless steel having higher rigidity and thickness than the compliance sheet 44. In a region of the support plate 45 facing the reservoir 43, a compliance opening 48 is formed by removing a part of the support plate 45 in a shape following the opening of the lower surface of the reservoir 43. For this reason, the opening on the lower surface side of the reservoir 43 is sealed only with the compliance sheet 44 having flexibility. In other words, the compliance sheet 44 defines a part of the reservoir 43.

  A portion corresponding to the compliance opening 48 on the lower surface of the support plate 45 is sealed by the fixing plate 23. Thereby, a compliance space 47 is formed between the flexible region of the compliance sheet 44 and the fixing plate 23 facing the flexible region. The flexible region of the compliance sheet 44 in the compliance space 47 is displaced toward the reservoir 43 side or the compliance space 47 side in accordance with the pressure fluctuation in the ink flow path, particularly in the reservoir 43. Therefore, the thickness of the support plate 45 is determined according to the height required for the compliance space 47.

  The actuator unit 26 and the communication plate 25 are fixed to the holder 28. The holder 28 has substantially the same shape as the communication plate 25 in a plan view, and an accommodation space 49 for accommodating the actuator unit 26 is formed on the lower surface side of the holder 28. Then, the lower surface of the holder 28 is sealed by the communication plate 25 in a state where the actuator unit 26 is accommodated in the accommodation space 49. As shown in FIG. 3, an insertion space 50 that communicates with the accommodation space 49 is formed at a substantially central portion of the holder 28 in plan view. The insertion space 50 communicates with the wiring space 40 of the actuator unit 26. The flexible board 39 is configured to be inserted into the wiring cavity 40 through the insertion cavity 50. In addition, an introduction liquid chamber 51 communicating with the reservoir 43 of the communication plate 25 is formed inside the holder 28 on both sides of the insertion space 50 and the accommodation space 49. In addition, an ink introduction port 52 communicating with the introduction liquid chamber 51 is opened on the upper surface of the holder 28. The ink sent from the ink cartridge 8 is introduced into the introduction liquid chamber 51 through the ink introduction port 52. That is, ink sent from the ink cartridge 8 is introduced into the ink introduction port 52, the introduction liquid chamber 51, and the reservoir 43, and is supplied from the reservoir 43 to the pressure chambers 33 through the individual communication ports 35. Note that the entire liquid chamber defined by the reservoir 43 and the introduction liquid chamber 51 in the present embodiment can be used as a common liquid chamber in the present invention.

The fixed plate 23 is a metal plate material such as stainless steel. In the present embodiment, the fixing plate 23 has a through-hole 23 a having a shape that follows the outer shape of the nozzle plate 24 in order to expose the nozzle 30 formed on the nozzle plate 24 at a position corresponding to the nozzle plate 24. It is formed so as to penetrate the direction. The through hole 23a communicates with the through apertures of the compliance substrate 27 is formed corresponding to the nozzle plate 24. In the present embodiment, the lower surface of the fixed plate 23 and the exposed portion of the nozzle plate 24 in the through hole 23a constitute a nozzle forming surface. The fixing plate 23 is fixed to a head case (not shown) that houses the recording head 10.

  In the recording head 10 having the above-described configuration, the drive signal (drive) from the drive IC 38 is filled in a state where the flow path from the ink inlet 52 to the nozzle 30 through the reservoir 43 and the pressure chamber 33 is filled with ink. When the piezoelectric element 31 is driven according to the pulse), a pressure fluctuation occurs in the ink in the pressure chamber 33, and the ink is ejected from a predetermined nozzle 30 due to the pressure fluctuation.

Next, a cleaning operation for forcibly discharging ink from the nozzles 30 of the recording head 10 in the printer 1 having the above-described configuration to restore the discharge capability of each nozzle 30 will be described.
FIG. 6 is a flowchart for explaining the flow of processing (control method) of the cleaning operation. FIG. 7 is a diagram for explaining the pressure acting on the ink in each nozzle 30 in the conventional cleaning operation, and is a schematic diagram showing the ink flow path from the reservoir 43 to the nozzle 30 in a simplified manner. . The hatched arrows in the figure schematically represent the strength (or flow rate) of the pressure acting on the ink in each nozzle 30 (and corresponding pressure chamber 33) during the cleaning operation. Therefore, the longer the length of the arrow, the stronger the pressure acting on the ink in the nozzle 30, and the shorter the length of the arrow, the weaker the pressure acting on the ink in the nozzle 30. As described above, in the reservoir 43 in this embodiment, the tapered surfaces 42 are provided on both sides in the nozzle row direction, so that the ink supply pressure from the reservoir 43 side to each nozzle 30 is made as uniform as possible. ing. However, at both ends of the reservoir 43 in the nozzle row direction, the ink path from the ink introduction port 52 to the nozzle 30 is longer than that at the central portion near the ink introduction port 52. It is easy to squeeze and bubbles B tend to accumulate. Therefore, as indicated by arrows in FIG. 7, the pressure in the cleaning operation (differential pressure inside and outside the nozzle 30) is less likely to act on the nozzles 30 at both ends of the nozzle row than the nozzle 30 at the center. Ink and bubble discharge efficiency decreases. For this reason, the strength in the cleaning operation (pressure applied to the ink in the flow path, the cleaning operation time, etc.) in order to discharge the thickened ink and air bubbles more reliably at the nozzles 30 located at both ends of the nozzle row, as a whole. If it is lifted up, the ink is excessively discharged from the central nozzle 30. As a result, there is a problem that the amount of ink consumed in the cleaning operation increases.

  In view of the above problems, the printer 1 according to the present invention performs assist driving for driving the piezoelectric element 31 corresponding to the nozzle 30 in order to cause more ink to flow through the nozzle 30 with low bubble discharge efficiency in the cleaning operation. It has a special feature. In the present embodiment, among the nozzles 30 constituting the same nozzle row, the nozzles 30 located at both ends in the nozzle row direction are the assist target nozzles 30a (a kind of the first nozzle in the present invention) to which assist driving is performed. (See FIG. 9). The assist target nozzle 30a is determined in accordance with the length of the path (liquid path) from the ink introduction port 52 to the nozzle 30 through the individual communication port 35 and the pressure chamber 33 (hereinafter referred to as path length). . For example, a lower limit value of the path length in which bubbles are likely to stay is obtained in advance through experiments or the like, and the nozzle 30 corresponding to a path length equal to or greater than this threshold (that is, greater than or equal to a predetermined value) is set as the assist target. The nozzle 30a is used. The remaining nozzles 30 other than the assist target nozzle 30a (that is, the path length is less than a predetermined value) are nozzles 30 in which assist driving is not performed in the present embodiment.

  When the execution timing of the cleaning operation comes, the CPU 17 controls the carriage moving mechanism 7 to move the recording head 10 to above the capping mechanism 13, and capping the nozzle formation surface of the recording head 10 with the cap 14 of the capping mechanism 13. (Step S1). Subsequently, the cleaning operation is disclosed in the capping state (step S2). That is, the pump unit 16 is operated to suck the sealing space in the cap 14, and a differential pressure is generated between the inside of the nozzle 30 (inside the ink flow path) and the outside of the nozzle 30 (sealing space of the cap 14). As a result, ink and bubbles in the recording head 10 are sucked from the nozzle 30 by the differential pressure and discharged into the sealed space of the cap 14. When the cleaning operation is started, assist driving is started by applying an assist driving pulse (a kind of first driving waveform in the present invention) described later to the piezoelectric element 31 corresponding to the assist target nozzle 30a. (Step S3).

  FIG. 8 is a waveform diagram for explaining an example of an assist drive pulse used for assist drive. The assist drive pulse Pa in the present embodiment has a contraction element p1, a hold element p2, and an expansion element p3. The contraction element p1 is a waveform element that raises the potential from the reference potential Eb to a pressurization potential EH1 that is higher than the reference potential Eb. The hold element p2 is a waveform element that maintains the pressurization potential EH1, which is the terminal potential of the contraction element p1, for the time th. The expansion element p3 is a waveform element that lowers the potential from the pressurization potential EH1 to the reference potential Eb. The potential difference between the reference potential Eb and the pressurization potential EH1 is the assist drive voltage Va of the assist drive pulse Pa.

  When the assist driving pulse Pa configured in this way is applied to the piezoelectric element 31, first, the central portion in the width direction of the piezoelectric element 31 is bent inside the pressure chamber 33 (side closer to the nozzle 30) by the contraction element p1. . As a result, the pressure chamber 33 contracts from the reference volume corresponding to the reference potential Eb to the contraction volume corresponding to the pressurization potential EH1. The ink in the pressure chamber 33 is pressurized by the contraction of the pressure chamber 33, and the meniscus in the nozzle 30 is pushed out to the ejection side (the side opposite to the pressure chamber 33 side). That is, the assist drive pulse Pa is a drive waveform that swings the meniscus in the assist target nozzle 30a to the discharge side. The contracted state of the pressure chamber 33 is maintained over the application period (th) of the hold element p2. Thereafter, when the expansion element p3 is applied, the central portion of the piezoelectric element 31 bends outside the pressure chamber 33 (the side away from the nozzle 30) to return to the reference state, and the pressure chamber 33 returns to the reference volume. Here, when the expansion element p3 is applied to the piezoelectric element 31 and the pressure chamber 33 expands, the meniscus is discharged on the discharge side according to the vibration (natural vibration) generated in the ink when the pressure chamber 33 contracts by the contraction element p1. The timing to move to is set. As a result, the vibration generated during driving by the contraction element p1 is canceled. As described above, the assist drive pulse Pa can increase the force of ink ejection by shaking the meniscus in the nozzle 30a toward the ejection side.

  By the assist drive by the assist drive pulse Pa, a pressure change that promotes the inflow of ink from the reservoir 43 to the assist target nozzle 30a can be generated in the pressure chamber 33 corresponding to the assist target nozzle 30a. That is, by continuously performing the assist drive on the assist target nozzle 30a during the cleaning operation, it is possible to supplement the pressure for discharging ink and bubbles from the assist target nozzle 30a. Accordingly, it is possible to positively generate an ink flow from the reservoir 43 toward the assist target nozzle 30a. In the present embodiment, the piezoelectric elements 31 corresponding to the nozzles 30 other than the assist target nozzle 30a are not driven during the cleaning operation.

  In this manner, the cleaning operation is performed while assist driving is continuously performed on the assist target nozzle 30a. Then, after the cleaning operation is performed for a predetermined time, the assist driving is ended (step S4), and the cleaning operation is ended (step S5). By ending the assist drive before the cleaning operation is ended, bubbles are prevented from being caught in the nozzle 30 due to a pressure change caused by the assist drive. In other words, even if bubbles are caught in the nozzle 30 by the assist drive, they are quickly discharged by the cleaning operation. If the cleaning operation is completed, post-processing is performed in the present embodiment (step S6). As this post-processing, for example, ink that has adhered to the nozzle formation surface by the cleaning operation is discharged from the nozzle formation surface by the wiping mechanism 11 or other types of ink or bubbles mixed in the nozzle 30 by the wiping operation are discharged. A flushing operation or the like is performed.

  FIG. 9 is a schematic diagram for explaining the pressure acting on each nozzle 30 in the cleaning operation according to the present embodiment. In the figure, the pressure acting on the ink in each of the nozzles 30 and 30a when the assist drive pulse Pa is supplied to the piezoelectric element 31 corresponding to the assist target nozzle 30a on which the assist operation is performed during the cleaning operation is shown. This is schematically shown (the same applies to FIGS. 10, 12, 14, and 15 below). Further, the pressure acting on the ink in the nozzles 30 and 30a by the cleaning operation is represented by the length of the hatched arrow, and the assist driving pulse Pa is supplied to the piezoelectric element 31 to act on the ink in the assist target nozzle 30a. The pressure is represented by the length of the white arrow. The length of the hatching arrow representing the strength of the pressure acting on the ink in the nozzle 30 is matched with the length of the hatching arrow representing the strength of the pressure acting on the ink in the nozzle 30a and the length of the white arrow. The length is almost the same. As described above, during the cleaning operation, the piezoelectric element 31 corresponding to the assist target nozzle 30a (that is, a part of the drive elements) is driven by the assist drive pulse Pa, so that it is compared with other nozzles 30. Thus, it is possible to generate a pressure change in the pressure chamber 33 corresponding to the assist target nozzle 30a so as to promote the inflow of ink into the assist target nozzle 30a, which is difficult to apply pressure during the cleaning operation (the white arrow in FIG. 9). Reference), the flow of ink from the reservoir 43 toward the assist target nozzle 30a can be positively generated. For this reason, since the path length is equal to or longer than a predetermined value and the structure is such that the flow is easy to stagnate at the end of the reservoir 43, the assist target nozzle 30a is less susceptible to pressure during the cleaning operation than the other nozzles 30. In this case, it is possible to increase the discharge efficiency of ink and bubbles. As a result, it is possible to reduce the amount of ink consumed in the cleaning operation as compared with a conventional cleaning operation in which no assist driving is performed.

  FIG. 10 is a schematic diagram for explaining the pressure acting on each nozzle 30 in the cleaning operation according to the second embodiment. In the first embodiment, the configuration in which the assist drive is performed with respect to the plurality of assist target nozzles 30a by the common assist drive pulse Pa with the constant assist drive voltage Va is illustrated, but is not limited thereto. In the present embodiment, assist drive pulses Pa having different assist drive voltages Va are applied to the plurality of assist target nozzles 30a according to the length of the path from the ink introduction port 52. That is, the assist drive pulse Pa with the assist drive voltage Va set higher is applied to the piezoelectric element 31 of the assist target nozzle 30a having a longer path length from the ink introduction port 52. As a result, as shown in FIG. 10, the assist target nozzle 30a, which is more difficult to apply pressure during the cleaning operation, compensates for a larger pressure (see the white arrow in FIG. 10). It becomes possible to discharge evenly.

FIG. 11 is a waveform diagram for explaining a modified example of the assist drive pulse Pa.
In each of the above embodiments, the trapezoidal assist drive pulse Pa is illustrated, but the present invention is not limited to this, and as shown in FIG. 11, the drive pulse (ejection drive pulse) used for ejecting ink is the assist drive pulse Pa. It can also be adopted as ′. The illustrated assist drive pulse Pa ′ has a preliminary expansion element p11, an expansion hold element p12, a contraction element p13, a contraction hold element p14, and an expansion return element p15. The pre-expansion element p11 is a waveform element that gradually lowers the potential from the reference potential Eb to the reduced potential EL1 lower than the reference potential Eb. The expansion hold element p12 is a waveform element that maintains the decompression potential EL1 that is the terminal potential of the preliminary expansion element p11 for a certain period of time. The contraction element p13 is a waveform element that rapidly increases the potential from the decompression potential EL1 to the pressurization potential EH2 that is higher than the reference potential Eb. The contraction hold element p14 is a waveform element that maintains the pressurization potential EH2 that is the terminal potential of the contraction element p13 for a predetermined time. The expansion return element p15 is a waveform element that lowers the potential from the pressurization potential EH2 to the reference potential Eb.

  When the assist driving pulse Pa ′ configured in this way is applied to the piezoelectric element 31, first, the central portion in the width direction of the piezoelectric element 31 is bent to the outside of the pressure chamber 33 by the preliminary expansion element p <b> 11. As a result, the pressure chamber 33 expands from the reference volume corresponding to the reference potential Eb to the reduced pressure volume corresponding to the reduced pressure potential EL1. The expansion speed of the pressure chamber 33 at this time is set moderately so as not to affect the discharge of ink from the nozzle 30 as much as possible. The expansion state of the pressure chamber 33 is maintained over the application period of the expansion hold element p12. Subsequently, the central portion in the width direction of the piezoelectric element 31 is bent inward of the pressure chamber 33 by the contraction element p13. As a result, the pressure chamber 33 rapidly contracts from the decompression volume corresponding to the decompression potential EL1 to the contraction volume corresponding to the pressurization potential EH1. The ink in the pressure chamber 33 is pressurized by the rapid contraction of the pressure chamber 33, the meniscus in the nozzle 30 is pushed out to the ejection side, and the discharge of the ink from the nozzle 30 is promoted. The contraction state of the pressure chamber 33 is maintained over the application period of the contraction hold element p14. Thereafter, when the expansion return element p15 is applied, the central portion of the piezoelectric element 31 bends outside the pressure chamber 33 to return to the reference state, and the pressure chamber 33 returns to the reference volume.

  In this embodiment, the assist drive voltage Va ′ (potential difference between the reference potential Eb and the pressurization potential EH2) of the assist drive pulse Pa ′ is set higher than the assist drive voltage Va of the assist drive pulse Pa. For this reason, the assist drive pulse Pa ′ is increased to such an extent that the pressure generated in the ink in the nozzle 30 (assist target nozzle 30a) and the pressure chamber 33 is ejected from the nozzle 30. In particular, the slope of the contraction element p13 (potential change rate per time) is set steeper than the slope of the expansion element p3 of the assist drive pulse Pa. If at least one of the voltage and the inclination of the contraction element is larger when compared with the assist drive pulse Pa, the vibration can be further increased. Therefore, by driving the piezoelectric element 31 corresponding to the assist target nozzle 30a, which is less susceptible to pressure during the cleaning operation, by this assist drive pulse Pa ', a larger pressure is compensated for, so that the discharge efficiency of ink and bubbles is further increased. Is possible.

  FIG. 12 is a schematic diagram for explaining the pressure acting on each nozzle 30 in the cleaning operation according to the third embodiment. In each of the above embodiments, the configuration in which the assist drive is performed by the assist drive pulse Pa with respect to the assist target nozzle 30a is illustrated, but the present invention is not limited thereto. In the present embodiment, the piezoelectric elements 31 corresponding to the nozzles 30b other than the nozzles 30 (that is, some drive elements) are described later in order to cause more ink to flow through the nozzles 30 with low bubble discharge efficiency in the cleaning operation. It is characterized in that it is driven by the interrupt driving pulse Pb (a kind of the second driving waveform in the present invention) to intentionally block the ink flow. In the present embodiment, among the nozzles 30 constituting the same nozzle row, the nozzles 30 located at both ends in the nozzle row direction are set as assist target nozzles 30a that require assistance in discharging ink and bubbles during the cleaning operation. On the other hand, the nozzle 30 located in the other central portion is set as an interrupt target nozzle 30b (a type of the second nozzle in the present invention) that is a target that inhibits the flow of ink. The assist target nozzle 30a and the interrupt target nozzle 30b are determined according to the path length from the ink introduction port 52 to the nozzle 30. That is, as in the first embodiment, the nozzle 30 corresponding to the path length equal to or greater than the threshold (that is, a predetermined value or more) is set as the assist target nozzle 30a, and the path is shorter than the threshold (that is, less than the predetermined value). The nozzle 30 corresponding to the length is the interrupt target nozzle 30b.

FIG. 13 is a waveform diagram showing an example of the interrupt drive pulse Pb.
The interrupt drive pulse Pb in the present embodiment has an expansion element p21, a hold element p22, and a contraction element p23. The expansion element p21 is a waveform element that lowers the potential from the reference potential Eb to the reduced potential EL2 that is lower than the reference potential Eb. The hold element p22 is a waveform element that maintains the decompressed potential EL2 that is the terminal potential of the expansion element p21 for a certain period of time. The contraction element p23 is a waveform element that increases the potential from the reduced pressure potential EL2 to the reference potential Eb. The potential difference between the reference potential Eb and the reduced potential EL2 is the interrupt drive voltage Vb of the interrupt drive pulse Pb.

  When the interrupt drive pulse Pb configured as described above is applied to the piezoelectric element 31, first, the central portion in the width direction of the piezoelectric element 31 is bent to the outside of the pressure chamber 33 by the expansion element p <b> 21. As a result, the pressure chamber 33 expands from the reference volume corresponding to the reference potential Eb to the expansion volume corresponding to the decompression potential EL2. By the expansion of the pressure chamber 33, the ink in the pressure chamber 33 is depressurized, and the meniscus in the nozzle 30 is drawn to the pressure chamber 33 side. That is, the interrupt drive pulse Pb is a drive waveform that swings the meniscus in the interrupt target nozzle 30b toward the pressure chamber 33. The expansion state of the pressure chamber 33 is maintained over the application period of the hold element p22. Thereafter, when the contraction element p23 is applied, the central portion of the piezoelectric element 31 is bent inside the pressure chamber 33 to return to the reference state, and the pressure chamber 33 returns to the reference volume. Here, when the contraction element p23 is applied to the piezoelectric element 31 and the pressure chamber 33 expands, the meniscus is on the pressure chamber 33 side according to the natural vibration generated in the ink when the pressure chamber 33 is expanded by the expansion element p21. The timing to move to is set. As a result, the vibration generated during driving by the expansion element p21 is canceled. As described above, the interrupt drive pulse Pb can weaken the ink ejection force by shaking the meniscus in the nozzle 30b toward the pressure chamber 33.

  Due to the interrupt drive by the interrupt drive pulse Pb, a pressure change that inhibits the inflow of ink to the interrupt target nozzle 30b in which the pressure during the cleaning operation is relatively easy due to the path length being shorter than the threshold value. It can be generated in the pressure chamber 33 corresponding to the target nozzle 30b (see the white arrow in FIG. 12). Accordingly, it is possible to promote the inflow of ink from the reservoir 43 to the assist target nozzle 30a. That is, the pressure for discharging ink and bubbles from the assist target nozzle 30a can be supplemented by the interrupt drive for the interrupt target nozzle 30b. Thereby, the flow of ink from the reservoir 43 toward the assist target nozzle 30a can be positively generated, and the discharge efficiency of ink and bubbles in the assist target nozzle 30a can be increased. As a result, the amount of ink consumed by the cleaning operation can be reduced. In this embodiment as well, as in the second embodiment, an interrupt drive pulse Pb having a different interrupt drive voltage Vb according to the length of the path from the ink introduction port 52 corresponds to the interrupt target nozzle 30b. 31 may be applied. Other configurations are the same as those in the first embodiment.

  FIG. 14 is a schematic diagram illustrating the flow of ink in the ink flow path in the cleaning operation according to the fourth embodiment. In each of the above embodiments, the configuration in which the ink introduction port 52 is disposed at a position corresponding to the central portion of the reservoir 43 in the nozzle row direction is illustrated, but the present invention is not limited to this. In the present embodiment, the two ink introduction ports 52 of the first ink introduction port 52a and the second ink introduction port 52b are arranged at positions deviated from the central portion in the nozzle row direction in the reservoir 43. In addition, two different threshold values are set for the path length from each of the ink introduction ports 52a and 52b to the nozzle 30: a first threshold value and a second threshold value shorter than the first threshold value. The nozzle 30 corresponding to the path length equal to or greater than the first threshold (that is, greater than or equal to the predetermined value) is set as the assist target nozzle 30a, and corresponds to the path length that is shorter than the second threshold (that is, less than the predetermined value). The nozzle 30 is the interrupt target nozzle 30b. Note that nozzles 30 corresponding to path lengths equal to or greater than the second threshold and less than the first threshold are the nozzles 30 that are not driven in the present embodiment. In other words, the nozzle 30 whose path length from either of the ink introduction ports 52a and 52b is equal to or larger than the second threshold and further equal to or larger than the first threshold is set as the assist target nozzle 30a, and the ink introduction ports 52a and 52b The nozzle 30 whose path length from any one is shorter than the first threshold and shorter than the second threshold is set as the interrupt target nozzle 30b.

  In the present embodiment, assist driving is performed on the piezoelectric element 31 corresponding to the assist target nozzle 30a (that is, a part of the drive elements) during the cleaning operation, while the piezoelectric element 31 corresponding to the interrupt target nozzle 30b (that is, the drive target nozzle 30b). , A part of the drive elements) is interrupt-driven, so that a pressure change that promotes the inflow of ink into the assist target nozzle 30a is generated in the pressure chamber 33 corresponding to the assist target nozzle 30a, and A pressure change that inhibits the inflow of the ink to the interrupt target nozzle 30b can be generated in the pressure chamber 33 corresponding to the interrupt target nozzle 30b. Thereby, the flow of ink from the reservoir 43 toward the assist target nozzle 30a can be positively generated, and the discharge efficiency of ink and bubbles in the assist target nozzle 30a can be increased. As a result, the amount of ink consumed by the cleaning operation can be reduced. Also in the present embodiment, as in the second embodiment, the piezoelectric element 31 corresponding to the assist target nozzle 30a has an assist drive pulse Pa having a different assist drive voltage Va according to the length of the path from the ink introduction port 52. Alternatively, an interrupt drive pulse Pb having a different interrupt drive voltage Vb may be applied to the piezoelectric element 31 corresponding to the interrupt target nozzle 30b. Further, a configuration is adopted in which all the nozzles 30 are set to either the assist target nozzle 30a or the interrupt target nozzle 30b, and all the piezoelectric elements 31 are driven by either the assist drive pulse Pa or the interrupt drive pulse Pb, respectively. It is also possible to do. Other configurations are the same as those in the first embodiment.

  FIG. 15 is a schematic diagram illustrating the flow of ink in the ink flow path in the cleaning operation according to the fifth embodiment. In the present embodiment, an ink inlet 52 is provided at one end of the reservoir 43 in the nozzle row direction, and an ink outlet 53 is provided at the other end in the nozzle row direction. The ink is introduced from the ink introduction port 52, and the ink in the reservoir 43 is led out from the ink outlet port 53 (see the black arrow in the figure). That is, the printer 1 in the present embodiment employs a configuration in which ink is circulated between the ink storage member (ink tank) and the recording head 10. In such a configuration, the pressure in the cleaning operation is more likely to be applied to the nozzle 30 closer to the ink introduction port 52, and the pressure in the cleaning operation is less likely to be applied to the nozzle 30 farther from the ink introduction port 52 (closer to the ink outlet port 53). For this reason, in the present embodiment as well, as in the fourth embodiment, the first threshold and the second threshold shorter than the first threshold are 2 for the path length from the ink introduction port 52 to the nozzle 30. Two different thresholds are set. The nozzle 30 corresponding to the path length equal to or greater than the first threshold (that is, greater than or equal to the predetermined value) is set as the assist target nozzle 30a, and corresponds to the path length that is shorter than the second threshold (that is, less than the predetermined value). The nozzle 30 is the interrupt target nozzle 30b. Note that nozzles 30 corresponding to path lengths equal to or greater than the second threshold and less than the first threshold are the nozzles 30 that are not driven in the present embodiment. Also in the present embodiment, assist driving is performed on the assist target nozzle 30a during the cleaning operation, while interrupt driving is performed on the interrupt target nozzle 30b, so that the ink flow from the reservoir 43 toward the assist target nozzle 30a is performed. This can be generated positively, and it is possible to increase the discharge efficiency of ink and bubbles in the assist target nozzle 30a. As a result, the amount of ink consumed by the cleaning operation can be reduced. Also in the present embodiment, as in the second embodiment, the piezoelectric element 31 corresponding to the assist target nozzle 30a has an assist drive pulse Pa having a different assist drive voltage Va according to the length of the path from the ink introduction port 52. Alternatively, an interrupt drive pulse Pb having a different interrupt drive voltage Vb may be applied to the piezoelectric element 31 corresponding to the interrupt target nozzle 30b. Further, a configuration is adopted in which all the nozzles 30 are set to either the assist target nozzle 30a or the interrupt target nozzle 30b, and all the piezoelectric elements 31 are driven by either the assist drive pulse Pa or the interrupt drive pulse Pb, respectively. It is also possible to do. Other configurations are the same as those in the first embodiment.

  In the above, ink or the like is discharged from the nozzle 30 by sucking the sealing space in the cap 14 with the nozzle formation surface of the recording head 10 capped by the cap 14 and generating a differential pressure inside and outside the nozzle 30. Although the configuration is exemplified, the configuration is not limited to this. For example, the present invention can be applied to a configuration in which a cleaning operation is performed by pressurizing an ink supply path upstream of the recording head 10 by a pressurizing mechanism (cleaning mechanism). In other words, the ink in the flow path is pressurized, and the ink and bubbles in the recording head 10 are discharged from each nozzle 30 using this pressure. Also in this case, as in the above embodiments, the assist target nozzle 30a or the interrupt target nozzle 30b is set according to the path length from the ink introduction port 52, and assist driving is performed for the assist target nozzle 30a during the cleaning operation. Or by performing interrupt driving on the interrupt target nozzle 30b, it is possible to increase the discharge efficiency of ink and bubbles in the assist target nozzle 30a. As a result, the amount of ink consumed by the cleaning operation can be reduced.

  Further, in each of the above-described embodiments, the so-called flexural vibration type piezoelectric element 31 is exemplified as the drive element. However, the present invention 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 of the exemplified driving pulses, the waveform changes in the potential change direction, that is, up and down (polarity). In addition, the actuator is not limited to the piezoelectric element, and other driving elements such as an electrostatic actuator may be employed.

  In the above description, the ink jet recording head 10 which is a kind of liquid ejection head has been described as an example. However, the present invention can also be applied to other liquid ejection heads and liquid ejection apparatuses including the same. For example, color material discharge heads used for the production of color filters such as liquid crystal displays, electrode material discharge heads used for electrode formation such as organic EL (Electro Luminescence) displays, FEDs (surface emitting displays), biochips (biochemical elements) The present invention can also be applied to a liquid discharge head including a plurality of bioorganic discharge heads and the like and a liquid discharge apparatus including the same.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Frame, 3 ... Platen, 4 ... Conveyance mechanism, 5 ... Guide rod, 6 ... Carriage, 7 ... Carriage moving mechanism, 8 ... Ink cartridge, 10 ... Recording head, 11 ... Wiping mechanism, 12 ... Wiper , 13 ... Capping mechanism, 14 ... Cap, 15 ... Drain tube, 16 ... Pump unit, 17 ... CPU, 18 ... Storage device, 19 ... Drive signal generation circuit, 20 ... Input / output interface, 23 ... Fixed plate, 24 ... Nozzle plate, 25 ... Communication plate, 26 ... Actuator unit, 27 ... Compliance substrate, 28 ... Holder, 29 ... Pressure chamber forming substrate, 30 ... Nozzle, 31 ... Piezoelectric element, 32 ... Protection substrate, 33 ... Pressure chamber, 34 ... Nozzle communication port, 35 ... Individual communication port, 36 ... Vibration plate, 38 ... Drive IC, 39 ... Flexible substrate, 40 Wiring empty part, 41 ... accommodating space, 42 ... tapered surface, 43 ... reservoir, 44 ... compliance sheet, 45 ... support plate, 46 ... through opening, 47 ... compliance space, 48 ... compliance opening, 49 ... accommodating empty part, 50 DESCRIPTION OF SYMBOLS ... Insertion empty part, 51 ... Introducing liquid chamber, 52 ... Ink introduction port, 53 ... Ink outlet, 55 ... Pressurizing mechanism, 56 ... Supply tube, 57 ... Pressure adjusting mechanism, 58 ... Flow path pump

Claims (6)

There are a plurality of nozzles that discharge liquid, a pressure chamber that communicates with the nozzle, and a plurality of drive elements that cause pressure fluctuations in the liquid in the pressure chamber, and the plurality of pressure chambers have a common liquid chamber that communicates in common. A liquid discharge head;
A cleaning mechanism for discharging liquid from each of the plurality of nozzles;
A drive waveform generation circuit that generates a drive waveform for driving at least some of the plurality of drive elements when the liquid is discharged from the plurality of nozzles by the cleaning mechanism;
A liquid ejection apparatus comprising: The liquid discharge head includes a liquid inlet for introducing liquid into the common liquid chamber,
The nozzle includes a first nozzle having a liquid path length from the liquid inlet to the nozzle having a predetermined value or more, and a second nozzle having a liquid path length less than the predetermined value. ,
2. The liquid according to claim 1, wherein at least one of the driving elements corresponding to the first nozzle and the driving elements corresponding to the second nozzle is the partial driving element. Discharge device. The liquid inlet is located at a central portion in the first direction of the common liquid chamber,
The first nozzle communicates with an end of the common liquid chamber in the first direction;
The liquid ejection apparatus according to claim 2, wherein the second nozzle communicates with the central portion of the common liquid chamber.   The drive waveform applied to the drive element corresponding to the first nozzle is a first drive waveform that swings a meniscus in the first nozzle to the discharge side. The liquid discharge apparatus as described.   5. The drive waveform applied to the drive element corresponding to the second nozzle is a second drive waveform that swings the meniscus in the second nozzle toward the pressure chamber. 6. The liquid ejection device according to item. There are a plurality of nozzles that discharge liquid, a pressure chamber that communicates with the nozzle, and a plurality of drive elements that cause pressure fluctuations in the liquid in the pressure chamber, and the plurality of pressure chambers have a common liquid chamber that communicates in common. A control method for a liquid discharge apparatus, comprising: a liquid discharge head; a cleaning mechanism that discharges liquid from each of the plurality of nozzles; and a drive waveform generation circuit that generates a drive waveform for driving the drive element,
A method of controlling a liquid ejection apparatus, wherein when the liquid is discharged from a plurality of nozzles by the cleaning mechanism, at least some of the plurality of driving elements are driven by the driving waveform.

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