JP2012245759A - Liquid jetting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the sum total of the liquid discharged from a plurality of nozzles by causing the difference of the discharge amount of the liquid from the plurality of nozzles to be small at purge time, without changing liquid jet characteristic from all nozzles.SOLUTION: An inkjet head 4 is the longest in flow channel length from an ink supply port 36 at purge time, and displaces the phase of the drive pulse signal that is applied to the individual electrode corresponding to two pressure chambers for purge adjacent to each other and only by the pulse width of pulse P. Moreover, the inkjet head 4 does not apply the drive pulse signal to the individual electrode corresponding to two pressure chambers for purge in the recording operation.

Description

  The present invention relates to a liquid ejecting apparatus that ejects liquid.

  Conventionally, in a liquid ejecting apparatus that ejects liquid from a nozzle, foreign matter, air, or the like is mixed in the liquid flow path communicating with the nozzle, or the liquid in the nozzle is dried and thickened. When the liquid ejecting performance of the nozzle is deteriorated, there is provided a means for executing the purge for forcibly discharging the foreign matter, air, or thickened liquid from the nozzle, and recovering the liquid ejecting performance from the nozzle. .

  As the above-described liquid ejecting apparatus, for example, Patent Document 1 discloses an ink jet printer that ejects ink from nozzles onto a recording medium to record characters and images. This ink jet printer has an ink jet head, a cap that is in close contact with the nozzle surface of the ink jet head and covers a plurality of nozzles, and a suction device connected to a suction port formed in the cap. Then, in a state where the cap is in close contact with the nozzle surface and a plurality of nozzles are covered with the cap, the inside of the cap is decompressed by the suction device and the ink is sucked out of the nozzle, so that foreign matter, air, etc. in the inkjet head can be removed together with the ink The purge to be discharged is executed.

  By the way, the liquid is supplied to the plurality of pressure chambers from the common liquid chamber communicating with the liquid supply port. The flow path lengths through the common liquid chamber from the liquid supply port to the plurality of pressure chambers are different from each other, and the longer the flow path length from the liquid supply port to the pressure chamber, the more the liquid supply port to the pressure chamber. The flow path resistance is increased. As described above, when the flow path resistance is different in each of the plurality of pressure chambers, the liquid supply speed from the liquid supply port to each nozzle is affected. Then, at the time of the purge, a nozzle having a larger flow path resistance is less likely to be supplied with liquid, and insufficient supply tends to occur.

  Therefore, if the suction force by the suction device at the time of purging is set based on the nozzle having the largest flow path resistance from the liquid supply port, more liquid than necessary from the nozzle communicating with the pressure chamber having the small flow path resistance. As a result, the sum of liquids discharged from a plurality of nozzles during purging has increased. In order to reduce the discharge amount of the liquid, in the ink jet head described in Patent Document 2, the nozzle having the largest flow path resistance among the plurality of nozzles that eject the liquid onto the recording paper during the recording operation By driving, the shortage of supply of liquid to the nozzle was resolved and the liquid was discharged.

JP 2008-221836 A (FIG. 1) JP 2010-89312A (FIG. 1)

  By the way, in the ink jet head described in Patent Document 2, all the nozzles that are driven in order to eliminate the shortage of liquid supply at the time of purging are nozzles that are used during the recording operation. Thus, unlike the recording operation, when the nozzle is driven in a state in which the negative pressure generated by the suction device is generated in the ink in the nozzle, the portion that deforms the pressure chamber is deformed by the negative pressure and is recessed. The nozzle will be driven to cause excessive deformation. Then, there is a possibility that mechanical damage such as cracks may occur in the portion that deforms the pressure chamber, and only the nozzle that is driven at the time of purging changes the liquid ejection characteristics as compared with other nozzles. For example, in the ink jet head described in Patent Document 2, a nozzle is driven by a piezoelectric element, and if the piezoelectric element is mechanically damaged, the piezoelectric characteristics change, and liquid ejection from the nozzle The characteristics will change.

  Accordingly, an object of the present invention is to provide a liquid ejected from a plurality of nozzles without changing the liquid ejection characteristics from all the nozzles and reducing the difference in the amount of liquid ejected from the plurality of nozzles at the time of purging. It is an object to provide a liquid ejecting apparatus that reduces the sum of the above.

  The liquid ejecting apparatus of the present invention is arranged along a liquid supply port, a common liquid chamber that communicates with the liquid supply port, extends in a predetermined direction, and extends in the common liquid chamber. A flow path unit having a plurality of pressure chambers communicating with the liquid chamber in common, and a plurality of nozzles communicating with the plurality of pressure chambers, respectively, and applying pressure to the liquid in the flow path unit from the outside of the flow path unit. Purge means for forcibly discharging the liquid from the plurality of nozzles to act, and the common liquid chamber is pressurized further downstream in the extending direction than the plurality of pressure chambers. Chambers are in communication with each other, further comprising an actuator for applying pressure to the plurality of pressure chambers and the liquid in the pressurizing chamber, wherein the actuator applies pressure to the liquid in the pressurizing chamber only when purging by the purge means. And grant When the liquid injection into the injection medium will not apply pressure to the liquid in the pressure chamber.

  According to the liquid ejecting apparatus of the present invention, when purging by the purging means, the actuator applies pressure to the liquid in the pressurizing chamber disposed downstream of the plurality of pressure chambers in the extending direction of the common liquid chamber. is doing. As a result, by causing a pressure difference locally at a position farther from the liquid supply port than the plurality of pressure chambers, the influence of the channel resistance of the common liquid chamber on the liquid flowing in the common liquid chamber is reduced, The amount of liquid discharged from the nozzle communicating with the pressure chamber can be increased. At this time, the discharge amount of the liquid increases as the nozzle communicates with the pressure chamber closer to the pressurizing chamber. Therefore, the difference in the discharge amount of the liquid from the nozzles communicating with the plurality of pressure chambers due to the difference in the channel length is reduced, and the pressure applied to the liquid in the channel unit by the purge unit is reduced, It is possible to suppress the wasteful discharge of the liquid from the nozzle. In addition, the pressurizing chamber is not used at the time of liquid ejection to the ejection target medium, but is used only at the time of purging, so even if the portion that deforms the pressurizing chamber is damaged, the portion that deforms the pressure chamber Will not be damaged, so the liquid ejection characteristics from all nozzles will not change.

  The flow path unit preferably has a purge nozzle communicating with the pressurizing chamber.

  According to this, by applying pressure to the pressurizing chamber, a liquid flow toward the pressurizing chamber is generated in the common liquid chamber. Then, due to the flow of the liquid toward the terminal pressurizing chamber, air is more likely to flow into the pressurizing chamber than the pressure chamber. Therefore, air can be discharged together with the liquid from the purge nozzle, and clogging of the pressure chamber and the nozzle can be suppressed. Note that the pressurizing chamber and the purge nozzle are not used when the liquid is ejected onto the ejection target medium, so there is no problem even if the air is clogged.

  At this time, the diameter of the purge nozzle is preferably larger than the diameters of the other nozzles.

  According to this, since the diameter of the purge nozzle is larger than the diameters of the other nozzles, a large amount of liquid can be quickly discharged from the purge nozzle as compared to the other nozzles. Therefore, the locally generated pressure difference is increased, and the influence of the channel resistance of the common liquid chamber on the liquid flowing in the common liquid chamber at the time of purging can be further reduced.

  The actuator includes a plurality of driving elements provided in the flow path unit and deforming the volumes of the plurality of pressure chambers and the pressurizing chamber, respectively, and driving for applying a driving pulse signal to the driving elements. And the drive device has a volume change in the pressurizing chamber larger than a volume change in the pressure chamber when the liquid is ejected onto the ejection target medium when purging by the purge means. A driving pulse signal may be applied to the driving element corresponding to the pressurizing chamber.

  According to this, the volume change of the pressurizing chamber is made larger than the volume change of the pressure chamber when the liquid is ejected onto the ejection target medium, and the drawing speed of the liquid into the pressurizing chamber is increased. Therefore, the locally generated pressure difference is increased, and the influence of the channel resistance of the common liquid chamber on the liquid flowing in the common liquid chamber at the time of purging can be further reduced.

  The flow path unit includes a plurality of the common liquid chambers and a plurality of pressurization chambers, and the plurality of common liquid chambers are arranged in parallel. , Communicating with the plurality of common liquid chambers, respectively, and arranged side by side along a direction intersecting the extending direction of the common liquid chamber, and the actuator includes the plurality of pressure chambers and the plurality of pressurizations A diaphragm joined to the flow path unit so as to cover the chamber, and a plurality of parts provided on the diaphragm and deforming portions of the diaphragm facing the plurality of pressure chambers and the plurality of pressurizing chambers, respectively. A drive device that further includes a drive device that applies a drive pulse signal to the drive device, the drive device between the two pressurizing chambers adjacent to each other when purging by the purge means. The phase of the drive pulse signal It may be Rashi.

  If a drive pulse signal having the same phase is applied to two drive elements corresponding to two adjacent pressure chambers, the timing at which the portions of the diaphragm facing the two pressure chambers are deformed is the same, so mutual interference (crosstalk) ) Is the largest, and the amount of displacement of the portion of the diaphragm facing the pressure chamber is small. On the other hand, as the phase difference between the drive pulse signals applied to the two drive elements is increased, the timing at which the portion of the diaphragm facing the two pressure chambers is deformed shifts, so the influence of crosstalk is reduced, and the diaphragm The amount of displacement at the portion facing the pressure chamber increases.

  Therefore, by shifting the phase of the drive pulse signal between two pressurizing chambers adjacent to each other, while reducing the power consumption without increasing the voltage of the drive pulse signal, compared to the case of the drive pulse signal of the same phase, The amount of displacement of the portion of the diaphragm facing the pressurizing chamber increases, and the speed of drawing liquid into the pressurizing chamber can be increased. Therefore, the locally generated pressure difference is increased, and the influence of the channel resistance of the common liquid chamber on the liquid flowing in the common liquid chamber at the time of purging can be further reduced.

  By reducing the difference in the amount of liquid discharged from the nozzles communicating with the plurality of pressure chambers due to the difference in the channel length, and by reducing the pressure applied to the liquid in the channel unit by the purge means, the plurality of nozzles It is possible to suppress the wasteful discharge of the liquid. In addition, the pressurizing chamber is not used at the time of liquid ejection to the ejection target medium, but is used only at the time of purging, so even if the portion that deforms the pressurizing chamber is damaged, the portion that deforms the pressure chamber Will not be damaged, so the liquid ejection characteristics from all nozzles will not change.

1 is a plan view illustrating a schematic configuration of an ink jet printer according to an embodiment. It is a top view of an inkjet head. (A) is the A section enlarged view of FIG. 2, (b) is the BB sectional drawing of (a). It is a block diagram which shows roughly the control system of an inkjet printer. It is a waveform of the drive pulse signal applied to an individual electrode. (A) is a schematic diagram of the vicinity of the diaphragm when the amount of displacement is minimized due to the influence of crosstalk, and (b) is a schematic diagram of the vicinity of the diaphragm when the amount of displacement is maximized due to the influence of crosstalk. FIG. It is a longitudinal cross-sectional view of the inkjet head at the time of purge. 6 is a plan view of an ink jet head according to Modification 1. FIG. FIG. 10 is a longitudinal sectional view of an ink jet head in Modification 2. FIG. 10 is a longitudinal sectional view of an ink jet head in Modification 3.

  Next, an embodiment of the present invention will be described. In the present embodiment, an ink jet printer that ejects ink onto recording paper and records characters, images, and the like will be described as an example. FIG. 1 is a plan view showing a schematic configuration of the ink jet printer according to the present embodiment.

  As shown in FIG. 1, an ink jet printer 1 (liquid ejecting apparatus) includes a platen 2 on which recording paper 20 is placed, a carriage 3 that can reciprocate in a scanning direction parallel to the platen 2, and a carriage 3 A mounted inkjet head 4, a transport mechanism 5 that transports the recording paper 20 in a transport direction orthogonal to the scanning direction, a maintenance unit 6 that performs various maintenance operations related to recovery and maintenance of the liquid ejection performance of the inkjet head 4, and an inkjet A control device 7 (see FIG. 4) that controls the entire printer 1 is included.

  On the upper surface of the platen 2, the recording paper 20 supplied from a paper feeding mechanism (not shown) is placed. Also, above the platen 2, two guide rails 10 and 11 extending in parallel in the left-right direction (scanning direction) in FIG. 1 are provided, and the carriage 3 has two guide rails in a region facing the platen 2. 10 and 11 is configured to be reciprocally movable in the scanning direction.

  Further, the two guide rails 10 and 11 extend further to the right side in FIG. 1 along the scanning direction than the platen 2, and the carriage 3 is connected to the recording paper 20 on the platen 2. It is configured to be movable from a facing area (recording area) to a position away from the platen 2, which is a non-recording area, in the right direction. Further, an endless belt 14 wound between two pulleys 12 and 13 is connected to the carriage 3. When the endless belt 14 travels and is driven by a carriage drive motor 15, the carriage 3 is moved to the endless belt 14. As the vehicle travels, it moves in the scanning direction.

  The inkjet head 4 is mounted on the lower part of the carriage 3, and the lower surface of the inkjet head 4 parallel to the upper surface of the platen 2 is an ink ejection surface 4 a (see FIG. 3B) where a plurality of nozzles 16 are opened. It has become. Then, ink is ejected from the plurality of nozzles 16 on the ink ejection surface 4 a onto the recording paper 20 placed on the platen 2.

  Further, four ink supply ports 36 (see FIG. 2) corresponding to the inks of the respective colors are provided on the upper surface of the inkjet head 4, and one ends of the four tubes 17 are connected to the four ink supply ports 36. Has been. The other end of each of the four tubes 17 is connected to a detachable cartridge mounting portion 9 for four ink cartridges 8 storing inks of the respective colors. Ink of each color supplied from four ink cartridges 8 through four tubes 17 is supplied to the inkjet head 4.

  Next, the inkjet head 4 will be described. FIG. 2 is a plan view of the inkjet head. 3A is an enlarged view of a portion A in FIG. 2, and FIG. 3B is a sectional view taken along line BB in FIG. As shown in FIGS. 2 and 3, the inkjet head 4 includes a plurality of nozzles 16, a flow path unit 30 in which a plurality of pressure chambers 34 communicating with the plurality of nozzles 16 are formed, and an upper surface of the flow path unit 30. And a piezoelectric actuator 31 that applies pressure to the ink in the pressure chamber 34.

  First, the flow path unit 30 will be described. As shown in FIG. 3B, the flow path unit 30 has a structure in which four plates are stacked, and a plurality of nozzles 16 are formed on the lower surface (ink ejection surface 4a) of the flow path unit 30. Has been. As shown in FIG. 2, the plurality of nozzles 16 are arranged in the transport direction and constitute four nozzle rows 33 arranged in the scanning direction. From the nozzles 16 belonging to the four nozzle rows 33, a total of four inks, black ink and three color inks (yellow, cyan, magenta), are ejected, respectively.

  The flow path unit 30 is formed with a plurality of pressure chambers 34 respectively communicating with the plurality of nozzles 16, and corresponding to the four nozzle rows 33, the plurality of pressure chambers 34 are also arranged in the transport direction. The pressure chamber rows are formed and arranged in four rows in the scanning direction. Furthermore, the flow path unit 30 is formed with four manifolds 35 that respectively extend in the transport direction and supply four color inks of black, yellow, cyan, and magenta to the four pressure chamber rows. . The four manifolds 35 have one end in the extending direction (the upper end in FIG. 2) connected to four ink supply ports 36 formed on the upper surface of the flow path unit 30. In other words, the ink supply port 36 is connected to one end of the manifold 35, and the pressure chamber rows are arranged along the extending direction of the manifold 35, and the plurality of pressure chambers 34 belonging to the pressure chamber row are connected to the ink supply port 36. The distances (flow path lengths) through the manifolds 35 are different.

  If necessary, among the plurality of pressure chambers 34, four pressure chambers 34 that are surrounded by the regions 80B and 80C, belong to each pressure chamber row, and have the longest distance from the communicating ink supply port 36 are purged. The pressure chambers 34B and 34C (pressurizing chambers) are used, and the remaining pressure chamber 34 surrounded by the region 80A is used as a recording pressure chamber 34A. The purge pressure chambers 34B and 34C are arranged adjacent to each other alternately in the scanning direction. Of the plurality of nozzles 16, the nozzle communicating with the recording pressure chamber 34A is referred to as a recording nozzle 16A, and the nozzles communicating with the purging pressure chambers 34B and 34C are referred to as purge nozzles 16B and 16C. As will be described in detail later, the recording pressure chamber 34A and the recording nozzle 16A are used during a recording operation for ejecting ink onto the recording paper 20, and are not used during purging described later. , 34C and the purge nozzles 16B and 16C are not used during the recording operation, but are used only during the purge.

  Next, the piezoelectric actuator 31 will be described. As shown in FIG. 3B, the piezoelectric actuator 31 includes a vibration plate 40 disposed on the upper surface of the flow path unit 30 so as to cover the plurality of pressure chambers 34, and a plurality of pressures on the upper surface of the vibration plate 40. The piezoelectric layer 41 is disposed so as to face the chamber 34, and the plurality of individual electrodes 42 are disposed on the upper surface of the piezoelectric layer 41 so as to correspond to the plurality of pressure chambers 34.

  The plurality of individual electrodes 42 positioned on the upper surface of the piezoelectric layer 41 are respectively connected to a driver IC 47 that drives the piezoelectric actuator 31, and a predetermined driving voltage is applied to the plurality of individual electrodes 42 from the driver IC 47 (driving device). A drive pulse signal having a ground potential is applied independently. The diaphragm 40 located on the lower surface of the piezoelectric layer 41 is made of a metal material, and serves as a common electrode facing the plurality of individual electrodes 42 with the piezoelectric layer 41 interposed therebetween. The diaphragm 40 is connected to the ground wiring of the driver IC 47 and is always held at the ground potential.

  When the drive voltage is applied from a driver IC 47 between a certain individual electrode 42 and a diaphragm 40 as a common electrode, the piezoelectric actuator 31 is a portion of the piezoelectric layer 41 (active portion) sandwiched between the two. R1: A volume change is caused in the pressure chamber 34 by piezoelectric deformation (piezoelectric strain) of the drive element, and pressure is applied to the ink in the pressure chamber 34. At this time, ink is ejected from the nozzle 16 communicating with the pressure chamber 34 to which pressure is applied.

  Returning to FIG. 1, the transport mechanism 5 has two transport rollers 18 and 19 disposed so as to sandwich the platen 2 in the transport direction, and is placed on the platen 2 by these two transport rollers 18 and 19. The recording sheet 20 is transported in the transport direction (downward in FIG. 1).

  The ink jet printer 1 then ejects ink from the ink jet head 4 that reciprocates in the scanning direction (left and right direction in FIG. 1) together with the carriage 3 onto the recording paper 20 placed on the platen 2. By transporting the recording paper 20 in the transport direction (front of FIG. 1) by the transport rollers 18 and 19, desired characters, images, and the like are recorded on the recording paper 20.

  Next, the maintenance unit 6 will be described. As shown in FIG. 1, the maintenance unit 6 is in contact with the ink ejection surface 4a of the inkjet head 4 at a position away from the platen 2 on one side in the scanning direction (right side in FIG. 1). A suction cap 21 covering the opening and a suction pump 23 connected to the suction cap 21 are provided. Note that the suction cap 21 and the suction pump 23 in the present embodiment correspond to the purge means in the present invention.

  The suction cap 21 is driven up and down by a cap up-and-down motor 25 (see FIG. 4), and is brought into and out of contact with the ink ejection surface 4a. When the suction cap 21 comes into contact (capping) with the ink ejection surface 4a, the suction cap 21 covers the plurality of nozzles 16 to define a sealed space. In this way, when the suction cap 21 is in the capping state, the suction pump 23 is driven to suck and reduce the pressure in the suction cap 21, so that the ink is discharged from all the nozzles 16 covered by the suction cap 21. It is forcibly discharged (hereinafter referred to as purge). This purging is performed when the ink ejection performance from the nozzle 16 is deteriorated. At the time of this purging, in this embodiment, the four purge pressure chambers 34B and 34C having the longest distance from the ink supply port 36 are used. The drive pulse signal is applied only to the individual electrode 42 corresponding to the above, and the corresponding active portion R1 is piezoelectrically deformed, so that the diaphragm 40 is deformed to cause a volume change in the pressure chamber 34.

  Next, the electrical configuration of the inkjet printer 1 will be described with reference to the block diagram of FIG. As shown in FIG. 4, the control device 7 includes a central processing unit (CPU) 50, a read only memory (ROM) 51, a random access memory (RAM) 52, and a bus 53 connecting them. Having a microcomputer. Also, the bus 53 controls an ASIC (Application Specific Integrated) that controls a driver IC 47 of the inkjet head 4, a carriage drive motor 15 that drives the carriage 3, a transport mechanism 5, a suction pump 23 of the maintenance unit 6, and a cap lifting / lowering motor 25. Circuit) 54 is connected. The ASIC 54 is connected to an external device PC (personal computer) 70 via an input / output interface (I / F) 58 so that data communication is possible.

  The ASIC 54 controls the driver IC 47 of the inkjet head 4 and the carriage drive motor 15 based on the print data input from the PC 70 during the recording operation, and also the driver of the inkjet head 4 during the purge. A head control circuit 61 that controls the IC 47 and the carriage drive motor 15 respectively, a conveyance control circuit 62 that similarly controls the conveyance mechanism 5 based on the print data, a suction pump 23 of the maintenance unit 6 and a cap lifting motor when purging 25, and the like are incorporated.

  Next, the head control circuit 61 will be described in detail. The head control circuit 61 has a drive waveform selection unit 64. The drive waveform selection unit 64 selects and determines one type from among four types of drive waveforms, which will be described later, during a recording operation or purge. The four types of drive waveforms are used in the recording operation, and eject three types of ink balls (small balls, medium balls, large balls) with different pulse widths and pulse numbers and different droplet diameters. The three types of recording drive waveforms are used at the time of purge, and the above-described three types of recording drive waveforms are composed of one type of purge drive waveform having a different pulse width and number of pulses. The purge driving waveform different from that for recording includes, for example, a waveform in which a plurality of pulses of AL (Acoustic Length) width for the purge pressure chambers 34B and 34C are overlapped without a stop pulse. By doing so, the diaphragm 40 can resonate and the amount of ink discharged can be increased.

  Specifically, the drive waveform selection unit 64 selects and determines one type from the three types of recording drive waveforms based on the print data input from the PC 70 during the recording operation. Then, the head control circuit 61 transmits the drive waveform selected by the drive waveform selection unit 64 as it is to the driver IC 47 during the recording operation, and generates a drive pulse signal having a predetermined voltage based on the drive waveform. Let The drive pulse signal is supplied to the individual electrode 42 corresponding to the recording pressure chamber 34A, whereby ink is ejected from the plurality of recording nozzles 16A corresponding to the individual electrode 42.

  Here, as described above, if a drive pulse signal is not applied to the individual electrodes 42 corresponding to the four purge pressure chambers 34B and 34C at the time of purging, a plurality of recordings are supplied from the ink supply port 36. If the flow path lengths of the manifolds 35 to the pressure chambers 34A are different, the flow path resistances are different, which affects the ink supply speed from the ink supply port 36 to each recording pressure chamber 34A. Thus, there was a difference in the amount of ink discharged from the plurality of recording nozzles 16A during the purge.

  Therefore, in the present embodiment, at the time of purging, a drive pulse signal is applied to the individual electrode 42 corresponding to the purge pressure chambers 34B, 34C, and the active part R1 corresponding to the individual electrode 42 is actively deformed. Thus, a pressure difference is locally generated at a position farther from the ink supply port 36 than the plurality of recording pressure chambers 34A. Specifically, the head control circuit 61 further includes a phase change unit 65 in addition to the drive waveform selection unit 64. As described above, the drive waveform selection unit 64 selects and determines the purge drive waveform from the four types of drive waveforms during the purge.

  The phase changing unit 65 sets the phase of the driving pulse signal based on the purge driving waveform selected by the driving waveform selecting unit 64 at the time of purging (that is, the timing of applying the driving pulse signal to the individual electrode 42) with respect to the scanning direction. The purge pressure chambers 34B and 34C adjacent to each other are shifted within one cycle (360 degrees). More specifically, the phase changing unit 65 sets the phase of the drive pulse signal applied to the individual electrode 42 corresponding to the purge pressure chamber 34B to the individual pressure chamber 34C adjacent to the purge pressure chamber 34B. The phase of the drive pulse signal applied to the electrode 42 is shifted by the pulse width (the drive pulse signal application timing is shifted by the pulse P application time).

  In the present embodiment, the drive pulse signal based on the purge drive waveform is a drive pulse signal having one pulse P in one cycle as shown in FIG. If the drive pulse signal shown in FIG. 5A is a drive pulse signal applied to the individual electrode 42 corresponding to the purge pressure chamber 34B, the pulse width from the rise time rt11 of the pulse P in this drive pulse signal is equal to the pulse width. The drive pulse signal shown in FIG. 5B in which the pulse P is generated at the delayed rising time rt12 becomes the drive pulse signal applied to the individual electrode 42 corresponding to the purge pressure chamber 34C.

  Then, the head control circuit 61 shifts the drive waveform selected by the drive waveform selection unit 64 to the phase changed by the phase change unit 65 during purging (that is, the drive pulse signal is applied to the individual electrode 42). This is transmitted to the driver IC 47 so as to shift the application timing, and the driver IC 47 is caused to generate a drive pulse signal having a predetermined voltage based on the drive waveform. The drive pulse signal is supplied to the individual electrodes 42 corresponding to the purge pressure chambers 34B and 34C, thereby deforming the portions of the diaphragm 40 that face the purge pressure chambers 34B and 34C during the purge. Thus, the amount of ink discharged from the purge nozzles 16B and 16C is increased. Here, in this embodiment, the purge is performed for 2 seconds, and the drive pulse signal having one pulse P in one cycle described above is applied at 20 kHz during the purge. That is, the drive pulse signal has a period of 50 μsec, and the portion of the diaphragm 40 facing the purge pressure chambers 34B and 34C is deformed 40,000 times during the purge. The purge time, the frequency of the drive pulse signal, and the application time of the drive pulse signal can be changed as appropriate.

  Here, the amount of ink ejected from the nozzle 16 by shifting the phase of the drive pulse signal applied to the individual electrode 42 corresponding to the adjacent pressure chamber 34 will be described with reference to FIG. FIG. 6A is a schematic view of the vicinity of the diaphragm when the amount of displacement is minimized due to the influence of crosstalk, and FIG. 6B is the vicinity of the diaphragm when the amount of displacement is maximized due to the influence of crosstalk. FIG. 6A and 6B, in order to explain the displacement amount of the vibration plate 40 in an easy-to-understand manner, the boundary portion between the plate of the flow path unit 30 joined to the vibration plate 40 and the pressure chamber 34, that is, vibration. The constrained end portion of the plate 40 is schematically indicated by a triangle, and illustration of the individual electrodes 42 and the like is omitted.

  For example, when a drive pulse signal having the same phase is applied to the individual electrodes 42 corresponding to the pressure chambers 34 adjacent to each other without shifting the phase, as shown in FIG. Since the timing at which the portion facing the chamber 34 is deformed is the same, the influence of mutual interference (crosstalk) is greatest, and the amount of displacement of the portion of the diaphragm 40 facing the pressure chamber 34 is small. On the other hand, as the phase of the drive pulse signal applied to the individual electrodes 42 corresponding to the pressure chambers 34 adjacent to each other is gradually shifted, the timing at which the portions of the diaphragm 40 facing the two pressure chambers 34 are deformed. As a result, the influence of the crosstalk is reduced, and the amount of displacement of the portion of the diaphragm 40 facing the pressure chamber 34 is increased. Since the deformation of the vibration plate 40 is not hindered, the displacement amount of the portion of the vibration plate 40 facing the pressure chamber 34 becomes large. From another viewpoint, the portions facing the pressure chambers 34 on both sides of the diaphragm 40 are pulled by the portions facing the central pressure chamber 34 and deformed upwardly. Thereafter, when the portions facing the pressure chambers 34 on both sides of the diaphragm 40 are deformed downward and convex, the vibration is excited and the deformation is easy to occur, and the displacement amount of the portion of the diaphragm 40 facing the pressure chambers 34 becomes large. .

  Then, with respect to the individual electrodes 42 corresponding to the pressure chambers 34 adjacent to each other, a drive pulse signal whose phase is shifted by the pulse width of the pulse P (for example, the two drives shown in FIGS. 5A and 5B). When the pulse signal) is applied, the voltage of the drive pulse signal applied to one individual electrode 42 rises (that is, the pulse P is applied), and the vibration plate 40 facing the pressure chamber 34 corresponding to the individual electrode 42 The part is deformed. Thereafter, the voltage of the drive pulse signal applied to one individual electrode 42 falls, the deformation of the portion of the diaphragm 40 facing the pressure chamber 34 corresponding to this individual electrode 42 returns, and the other individual electrode 42 The voltage of the applied drive pulse signal rises, and the portion of the diaphragm 40 facing the pressure chamber 34 corresponding to the individual electrode 42 is deformed. At this time, as shown in FIG. 6B, the force corresponding to the other individual electrode 42 is utilized by using the force of returning the deformation of the portion of the diaphragm 40 facing the pressure chamber 34 corresponding to the one individual electrode 42. The portion of the diaphragm 40 that faces the pressure chamber 34 is greatly deformed. Therefore, the diaphragm 40 can be greatly deformed efficiently, and the displacement amount is maximized.

  In the present embodiment, at the time of purging, the purge pressure chambers 34B and 34C are arranged farther from the ink supply port 36 than the plurality of recording pressure chambers 34A and on the downstream side in the extending direction of the manifold 35. A portion of the vibration plate 40 is deformed, and a larger amount of ink is discharged from the purge nozzles 16B and 16C than the recording nozzle 16A. As described above, by locally generating a pressure difference at a position farther from the ink supply port 36 than the plurality of recording pressure chambers 34A, the influence of the flow path resistance of the manifold 35 on the ink flowing in the manifold 35 is reduced. In addition, the amount of ink discharged from the recording nozzles 16A communicating with all the recording pressure chambers 34A can be increased. At this time, the amount of ink discharged increases as the recording nozzle 16A communicates with the recording pressure chamber 34A close to the purge pressure chambers 34B and 34C. As a result, as shown in FIG. 7, the amount of ink discharged from the recording nozzles 16A communicating with the plurality of recording pressure chambers 34A due to the difference in flow path length during purging can be made substantially uniform. It is possible to reduce the suction force by the suction pump 23 to suppress wasteful discharge of ink from the plurality of nozzles 16 and to reduce the total sum of ink discharged from the plurality of nozzles 16.

  Further, the purge pressure chambers 34B and 34C are not used during the recording operation, but are used only during the purge operation. Therefore, the portions for deforming the purge pressure chambers 34B and 34C (the vibration plate 40, the individual electrode 42, etc.) Is damaged, the portion that deforms the recording pressure chamber 34A is not damaged, and the ink ejection characteristics from all the recording nozzles 16A do not change.

  Further, by applying pressure to the purge pressure chambers 34B and 34C, an ink flow toward the purge pressure chambers 34B and 34C is generated in the manifold 35. Then, the ink flows toward the purge pressure chambers 34B and 34C at the end, so that air is more likely to flow into the purge pressure chambers 34B and 34C together with the ink than the recording pressure chamber 34A. Therefore, it is difficult for air to flow into the recording pressure chamber 34A and the recording nozzle 16A communicating with the recording pressure chamber 34A, and it is possible to suppress clogging of the recording pressure chamber 34A and the recording nozzle 16A. Note that the purge pressure chambers 34B and 34C and the purge nozzles 16B and 16C are not used during the recording operation on the recording paper 20, so there is no problem even if the air is clogged.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, those having the same configuration as that of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.

  In the present embodiment, one purge pressure chamber 34B, 34C is disposed at the end with respect to one manifold 35, but a plurality of pressure chambers 134 communicating with one manifold 35 as shown in FIG. Among these, the pressure chambers surrounded by the regions 180B and 180C, respectively, and the pressure chambers farthest from the ink supply port 36 and the pressure chambers adjacent to the pressure chambers as the purge pressure chambers 134B and 134C are surrounded by the region 180A. The remainder may be used as the recording pressure chamber 134A (Modification 1). Then, the phase of the drive pulse signal is shifted between the two purge pressure chambers 134B and 134C as described above. As a result, the vibration plate 40 is efficiently deformed, and a local pressure difference generated at a position farther from the ink supply port 36 than the plurality of recording pressure chambers 134A becomes larger. The influence of the flow path resistance of the manifold 35 on the flowing ink can be further reduced.

  In this embodiment, the recording pressure chamber 34A and the purge pressure chambers 34B and 34C and the recording nozzle 16A and the purge nozzles 16B and 16C have the same shape. In order to improve the speed of ink drawing into the chambers 34B and 34C (the amount of ink discharged from the purge nozzles 16B and 16C), these shapes can be appropriately changed.

  For example, in this embodiment, the diameters of the recording nozzle 16A and the purge nozzles 16B and 16C are the same, but as shown in FIG. 9, the diameter of the purge nozzle 216B (216C) is the diameter of the recording nozzle 216A. (Modification 2). As a result, a larger amount of ink can be quickly discharged from the purge nozzle 216B (216C) than the recording nozzle 216A. Therefore, the local pressure difference generated at a position farther from the ink supply port 36 than the plurality of recording pressure chambers 34A becomes larger, and the influence of the flow path resistance of the manifold 35 on the ink flowing in the manifold 35 during the purge is affected. It can be further reduced.

  Further, as shown in FIG. 10, the purge pressure chamber 334B (334C) and the size of the individual electrode 342B facing the purge pressure chamber 334B (334C) are set to the individual electrode 342A facing the recording pressure chamber 334A. It may be larger than the size (Modification 3). At this time, since the displacement amount of the vibration plate 40 is increased, a large amount of ink can be quickly discharged from the purge nozzles 316B and 316C as compared with the recording nozzle 316A.

  Further, in the present embodiment, the purge pressure chambers 34B and 34C communicate with the purge nozzles 16B and 16C, but the purge nozzles 16B and 16C are not formed, and the purge pressure chambers 34B and 34C , Upstream of the plurality of recording pressure chambers 34 </ b> A in the direction of ink flow, for example, the ink supply port 36, and the upstream side and the downstream side of the plurality of recording pressure chambers 34 </ b> A without passing through the manifold 35. May be circulated.

  Further, in the present embodiment, the purge driving waveform dedicated to the purge is used as the driving waveform. However, the purge driving waveform is not used, and the purge driving waveform is used for the recording operation. Drive pulse waveform may be generated. By using a purge driving waveform dedicated to purging, the waveform can be set freely. For example, it is set so that ink is discharged to a minimum and minimum from the nozzle communicating with the pressure chamber with the longest flow path length. If so, the difference in the discharge amount of the liquid discharged from the plurality of nozzles can be further reduced.

  In addition, in this embodiment, the suction cap 21 is capped, and the suction pump 23 is driven to suck and reduce the pressure in the suction cap 21, so that all the nozzles 16 covered by the suction cap 21 The ink is forcibly discharged. For example, the flow path unit is applied by any method such as applying pressure to the ink supply port 36 toward the manifold 35 to forcibly discharge the ink from all the nozzles 16. A purge that forcibly ejects ink from the plurality of nozzles 16 by applying pressure to the ink in the manifold 35 from the outside of the nozzle 30 may be used.

  Furthermore, in this embodiment, as a driving method of the piezoelectric actuator 31 of the inkjet head 4, the piezoelectric layer 41 is not deformed in the standby state, and an electric field is applied to the piezoelectric layer 41 when a driving pulse signal (pulse P) is applied. A method in which pressure is applied to the ink in the pressure chamber 34 by the deformation of the piezoelectric layer 41 caused by the above-described action, a so-called pushing method, has been described as an example. However, the driving method of the piezoelectric actuator 31 is not limited to this pushing method and may be a pulling method.

  In this embodiment, the phase of the drive pulse signal applied to the individual electrode 42 corresponding to the purge pressure chambers 34B and 34C is shifted, but the phase of these drive pulse signals may be the same phase.

  Furthermore, in the present embodiment, the four pressure chamber rows are arranged. However, the pressure chamber rows are not limited to four rows, but may be a plurality of rows or may be arranged in only one row.

  In this embodiment, the present invention is applied to an ink jet printer that records characters and images by ejecting ink onto recording paper. However, the application target of the present invention is used for such applications. It is not limited to things. In other words, the present invention can be applied to various liquid ejecting apparatuses that eject various types of liquids other than ink onto a target according to the application.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 4 Inkjet head 6 Maintenance unit 16 Nozzle 21 Suction cap 23 Suction pump 30 Flow path unit 31 Piezoelectric actuator 34A Recording pressure chamber force chamber 34B, 34C Purge pressure chamber 35 Manifold 36 Ink supply port R1 Active part

Claims (5)

A liquid supply port, a common liquid chamber that communicates with the liquid supply port and extends in a predetermined direction, and a plurality that are disposed along the extending direction of the common liquid chamber and communicate with the common liquid chamber in common A flow path unit having a pressure chamber and a plurality of nozzles respectively communicating with the plurality of pressure chambers;
Purge means for forcibly discharging liquid from the plurality of nozzles by applying pressure to the liquid in the flow path unit from the outside of the flow path unit, and
A pressure chamber communicates with the common liquid chamber further downstream in the extending direction than the plurality of pressure chambers,
An actuator for applying pressure to the liquid in the plurality of pressure chambers and the pressurizing chamber;
The actuator applies pressure to the liquid in the pressurizing chamber only when purging by the purging unit, and does not apply pressure to the liquid in the pressurizing chamber when liquid is injected onto the ejection target medium. Liquid ejector.   The liquid ejecting apparatus according to claim 1, wherein the flow path unit includes a purge nozzle that communicates with the pressurizing chamber.   The liquid ejecting apparatus according to claim 2, wherein a diameter of the purge nozzle is larger than a diameter of the other nozzle. The actuator includes a plurality of driving elements that are provided in the flow path unit and deform the volumes of the plurality of pressure chambers and the pressure chamber, respectively.
A driving device for applying a driving pulse signal to the driving element;
The drive device outputs a drive pulse signal that causes a change in volume of the pressurizing chamber to be larger than a change in volume of the pressure chamber when liquid is ejected onto the ejection target medium when purging by the purge means. The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is applied to the driving element corresponding to the pressurizing chamber. The flow path unit has a plurality of the common liquid chambers and a plurality of pressure chambers,
A plurality of the common liquid chambers are arranged in parallel,
The plurality of pressurizing chambers communicate with the plurality of common liquid chambers, respectively, and are arranged side by side along a direction intersecting the extending direction of the common liquid chamber,
The actuator includes a diaphragm joined to the flow path unit so as to cover the plurality of pressure chambers and the plurality of pressurizing chambers, and the plurality of pressure chambers of the diaphragm provided on the diaphragm. A plurality of driving elements that respectively deform the portions facing the plurality of pressurizing chambers;
A driving device for applying a driving pulse signal to the driving element;
4. The drive device according to claim 1, wherein the drive device shifts the phase of the drive pulse signal between the two pressurizing chambers adjacent to each other when purging by the purge unit. 5. Liquid ejector.

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