JP2016159574A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device capable of performing a vibrating operation neither too much nor too little.SOLUTION: With a drive signal vCOM, first vibration drive pulses VP1, VP2 to be raised in potential up to a reference potential Vb as reference for potential variation after being lowered in potential from the reference potential, and second vibration drive pulses VP3, VP4 to be lowered in potential down to the reference potential after being raised in potential from the reference potential are generated within a repetitive period T, and a control circuit applies an actuator selectively with one or a plurality of the first vibration drive pulses or second vibration drive pulses of a drive signal according to a condition associated with thickening of the ink or a condition associated with sedimentation of a component included in the ink, thereby performing a vibration operation.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet recording apparatus, and in particular, a liquid that causes the actuator to be driven by applying a driving pulse to the actuator to cause pressure oscillation in the liquid in the pressure chamber, thereby ejecting the liquid from the nozzle. The present invention relates to a liquid ejection apparatus including an ejection head.

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

  Here, the liquid discharge head drives an actuator such as a piezoelectric element or a heat generating element to cause pressure vibration in the liquid in the pressure chamber communicating with the nozzle, and the liquid is discharged from the nozzle using the pressure vibration. Discharge. In this type of liquid ejection head, since the liquid (meniscus) is exposed to the outside air at the nozzle, the liquid may thicken due to evaporation of the solvent component contained in the liquid. In addition, in a liquid containing a color material having a relatively large specific gravity, the color material or the like may settle over time. In such cases, there is a possibility that the liquid is not normally ejected from the nozzle. In order to suppress such a problem, an actuator (for example, a piezoelectric element or the like) corresponding to a nozzle from which liquid is not discharged during a liquid discharging operation (for example, a printing operation in a printer) or in a standby state where no liquid discharging operation is performed. By applying a vibration drive pulse to a heating element or the like to drive the actuator, the liquid and meniscus in the pressure chamber are vibrated to the extent that the liquid is not discharged from the nozzle. That is, by this vibration operation, the liquid in the vicinity of the nozzle is agitated and the thickening is suppressed (for example, see Patent Document 1).

JP 2014-138996 A

  Conventionally, the vibration operation is performed uniformly using the same vibration drive pulse. However, depending on the composition of the liquid, the discharge frequency for each nozzle, etc., the effect of the vibration operation is excessive or insufficient.

  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 performing a vibration operation without excess or deficiency.

[Means 1]
The liquid discharge apparatus of the present invention has been proposed to achieve the above object, and generates pressure vibrations in the liquid in the nozzle surface on which the nozzle for discharging the liquid is formed and in the pressure chamber communicating with the nozzle. A liquid ejection head having an actuator to be
A drive signal generation circuit that periodically generates a drive signal including a vibration drive pulse that drives the actuator to cause the liquid in the pressure chamber to vibrate and cause the liquid to vibrate;
A capping mechanism for sealing the nozzle surface of the liquid discharge head;
A control circuit for controlling the vibration operation by applying the vibration drive pulse to the actuator in a state where the nozzle surface of the liquid discharge head is sealed by the capping mechanism;
With
The drive signal includes a first vibration drive pulse that lowers the potential from a reference potential that is a reference for potential change and then increases the potential to the reference potential, and increases the potential from the reference potential to the reference potential. Generating at least one second vibration drive pulse for lowering the potential within a repetition period;
The control circuit may select either the first vibration drive pulse or the second vibration drive pulse from the drive signal according to a condition related to liquid thickening or a condition related to sedimentation of components contained in the liquid. One or more are selectively applied to the actuator to execute the vibration operation.

  According to the configuration of the means 1, the first vibration drive pulse or the second vibration drive pulse is selected from the drive signals according to the condition related to the thickening of the liquid or the condition related to the sedimentation of the component contained in the liquid. By selectively applying any one or a plurality to the actuator and executing the vibration operation, it is possible to reflect the various conditions and execute a more appropriate vibration operation without excess or deficiency.

[Means 2]
In the configuration of the means 1, the drive signal employs a configuration in which a plurality of first vibration drive pulses having different voltages and a plurality of second vibration drive pulses having different voltages are generated within a repetition cycle. It is desirable.

  According to the configuration of the means 2, the range of selection of the vibration drive pulse is widened, and the vibration operation can be executed more efficiently by combining these.

2 is a block diagram illustrating an electrical configuration of a printer. FIG. 2 is a perspective view illustrating an internal configuration of the printer. FIG. FIG. 3 is a cross-sectional view illustrating a configuration of a recording head. It is a wave form diagram explaining the structure of a drive signal. It is a wave form diagram which illustrated the selection pattern of the vibration drive pulse in vibration operation.

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

  FIG. 1 is a block diagram illustrating the electrical configuration of the printer 1, and FIG. 2 is a perspective view illustrating the internal configuration of the printer 1. The printer 1 in this embodiment includes a print engine 13 including a paper feed mechanism 3, a carriage moving mechanism 4, a linear encoder 5, a recording head 6, and the like, and a printer controller 7 that controls each unit. The recording head 6 is attached to the bottom surface side of the carriage 16 on which the ink cartridge 17 is mounted. The carriage 16 is configured to reciprocate along the guide rod 18 by the carriage moving mechanism 4. That is, the printer 1 sequentially transports the recording medium S such as recording paper by the paper feeding mechanism 3 and moves the recording head 6 relative to the recording medium in the width direction (main scanning direction) of the recording medium S. By ejecting ink from the nozzles 30 (see FIG. 3 and the like) of the recording head 6 and landing the ink on the recording medium S, an image or the like is recorded. It is also possible to adopt a configuration in which the ink cartridge 17 is disposed on the main body side of the printer, and the ink of the ink cartridge 17 is sent to the recording head 6 side through a supply tube.

  One end of the carriage 16 in the scanning direction (right front in FIG. 2) is a home position, and a capping mechanism 20 capable of sealing the nozzle surface of the recording head 6 is disposed below the home position. ing. The capping mechanism 20 includes a cap 21 made of a tray-like elastic material whose upper surface is open, and a pump (not shown) that creates a negative pressure in the internal space of the cap 21 in a state where the nozzle surface is sealed. Further, the capping mechanism 20 is configured to be moved up and down by a lifting mechanism (not shown), and is switched between a sealed state in which the cap 21 seals the nozzle surface of the recording head 6 and a retracted state in which the cap 21 is separated from the nozzle surface. Can be done. Specifically, when the recording head 6 is in a standby state in which the recording operation (printing operation) is not performed on the recording medium S, or when the printer 1 is turned off, the carriage 16 is positioned at the home position. Then, the nozzle surface of the recording head 6 is capped by the capping mechanism 20. As a result, the evaporation of the ink solvent from the nozzles 30 of the recording head 6 is suppressed. Further, in the capped state, a vibration operation described later is performed, and the ink in the nozzle 30 and the pressure chamber 31 of the recording head 6 is agitated. Further, in a maintenance operation (suction cleaning operation) that is a process of removing clogged nozzles 30 by removing thickened ink or bubbles in the flow path in the recording head 6, the pump is operated in the capping state. Thus, the negative pressure is applied to the internal space of the cap 21, thereby forcibly discharging ink and bubbles from the nozzle into the cap 21. The waste ink discharged to the cap 21 is discharged to a waste ink tank (not shown).

  The printer controller 7 in the present embodiment includes an interface (I / F) 8, a CPU 9, a memory 10, and a drive signal generation circuit 11. The interface 8 transmits / receives print data, a print command, and the like to / from an external device. The CPU 9 is an arithmetic processing device for controlling the entire printer. The memory 10 is an element that stores a program for the CPU 9 and data used for various controls, and includes a ROM, a RAM, and an NVRAM (nonvolatile storage element). The CPU 9 controls each unit according to a program stored in the memory 10. Further, the CPU 9 in the present embodiment generates ejection data indicating at which timing from which nozzle 30 ink is ejected during a recording operation based on print data from an external device, and the ejection data is used as the head of the recording head 6. Transmit to the controller 15. The drive signal generation circuit 11 generates an analog signal based on waveform data relating to the waveform of the drive signal, and amplifies the signal to generate a drive signal.

  Next, the print engine 13 will be described. As shown in FIG. 1, the print engine 13 includes a paper feed mechanism 3, a carriage moving mechanism 4, a linear encoder 5, a recording head 6, and the like. The carriage moving mechanism 4 includes a carriage 16 to which a recording head 6 which is a kind of liquid ejection head is attached, a drive motor (for example, a DC motor) that drives the carriage 16 via a timing belt or the like (see FIG. The recording head 6 mounted on the carriage 16 is moved in the main scanning direction. The paper feed mechanism 3 includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds the recording medium S onto the platen to perform sub-scanning. Further, the linear encoder 5 outputs an encoder pulse corresponding to the scanning position of the recording head 6 mounted on the carriage 16 to the printer controller 7 as position information in the main scanning direction. The CPU 9 of the printer controller 7 can grasp the scanning position (current position) of the recording head 6 based on the encoder pulse received from the linear encoder 5 side. Further, the CPU 9 generates a timing signal (latch signal LAT) that defines a generation timing of a drive signal COM described later based on the encoder pulse. The head controller 15 functions as a control circuit in the present invention, and performs control to selectively apply the drive pulse in the drive signal COM sent from the printer controller 7 side to each piezoelectric element 27.

FIG. 3 is a cross-sectional view of a main part for explaining the internal configuration of the recording head 6.
The recording head 6 in the present embodiment is schematically configured from a nozzle plate 25, a flow path substrate 26, a piezoelectric element 27, and the like, and is attached to the case 28 in a state where these members are laminated. The nozzle plate 25 is a member made of a silicon single crystal substrate in which a plurality of nozzles 30 are arranged in a line along the same direction at a pitch corresponding to the dot formation density. In the present embodiment, a nozzle row (a type of nozzle group) composed of a plurality of nozzles 30 arranged side by side is composed of, for example, 360 nozzles 30. The surface of the nozzle plate 25 on which ink is ejected corresponds to the nozzle surface.

  In the flow path substrate 26, a plurality of empty portions to be the pressure chambers 31 are formed corresponding to the respective nozzles 30. A common liquid chamber 32 that is an empty portion common to the pressure chambers 31 is formed outside the row of pressure chambers 31 in the flow path substrate 26. The common liquid chamber 32 communicates with each pressure chamber 31 via an ink supply port 33. Further, the ink from the ink cartridge side is introduced into the common liquid chamber 32 through the ink introduction path 34 of the case 28. A piezoelectric element 27 (a kind of actuator) is formed on the upper surface of the flow path substrate 26 opposite to the nozzle plate 25 via an elastic film 35. The piezoelectric element 27 is formed by sequentially laminating a metal lower electrode film, a piezoelectric layer made of, for example, lead zirconate titanate, and the like, and an upper electrode film made of metal (both not shown). Yes. The piezoelectric element 27 is a so-called flexural mode piezoelectric element and is formed so as to cover the upper portion of the pressure chamber 31. The piezoelectric element 27 is deformed when a drive signal is applied through the wiring member 36. Thereby, pressure vibration is generated in the ink in the pressure chamber 31 corresponding to the piezoelectric element 27, and ink is ejected from the nozzle 30 by controlling the pressure vibration of the ink.

  FIG. 4 is a waveform diagram for explaining an example of the drive signal generated by the drive signal generation circuit 11 and shows the drive signal vCOM used for the vibration operation. In the present embodiment, a unit period T that is a repetition period of the drive signal vCOM is defined by a latch signal LAT that is a timing signal generated based on an encoder pulse corresponding to the scanning position of the recording head 6. The drive signal vCOM is a drive signal used when the vibration operation is performed in the capping state by the capping mechanism 20 during the standby state in which the recording head 6 is not performing the recording operation (printing operation) on the recording medium S. The vibration operation is an operation for generating pressure vibration in the ink in the pressure chamber 31 for the purpose of stirring the ink in the nozzle 30 or the pressure chamber 31.

  In the drive signal vCOM in the present embodiment, a total of four vibration drive pulses VP1 to VP4 (a kind of vibration drive pulse in the present invention) are generated within a unit period T. More specifically, the unit period T is divided into a total of four pulse generation periods t1 to t4, and the first vibration drive pulse VP1 is the second pulse generation period t2 in the first pulse generation period t1. The second vibration drive pulse VP2 is generated at the third pulse generation cycle t3, and the third vibration drive pulse VP1 is generated at the first pulse generation cycle t1. In the capping state, any one or a plurality of vibration drive pulses in the drive signal vCOM are selected and applied.

  Each of the vibration drive pulses VP1 to VP4 included in the drive signal vCOM is a drive whose waveform and voltage are determined so as to cause pressure vibration in the ink in the nozzle 30 and the pressure chamber 31 to the extent that ink is not ejected from the nozzle 30. It is a pulse. The first vibration drive pulse VP1 corresponds to the first vibration drive pulse in the present invention, and the potential drops from the reference potential Vb serving as a reference for potential change to the first expansion potential VL1 lower than the reference potential Vb. It has an expansion component p1, a first expansion hold component p2 that holds the first expansion potential VL1 for a certain period of time, and a first return contraction component p3 that raises the potential from the first expansion potential VL1 to the reference potential Vb. The reference potential Vb is an initial potential corresponding to the reference volume of the pressure chamber 31. The reference volume is a volume (initial volume) that is a starting point of expansion or contraction of the pressure chamber 31. When the first vibration drive pulse VP1 is applied to the piezoelectric element 27, the piezoelectric element 27 is directed from the reference position corresponding to the reference potential Vb to the outside of the pressure chamber 31 (side away from the nozzle 30) by the first expansion component p1. Thus, the pressure chamber 31 is expanded from the reference volume to the first expansion volume corresponding to the first expansion potential VL1. This expansion state is maintained during the application period of the first expansion hold component p2. Thereafter, the first return contraction component p3 bends from the outside of the pressure chamber 31 to the inside (side approaching the nozzle 30) and is displaced to the reference position. Thereby, the pressure chamber 31 contracts from the first expansion volume to the reference volume. That is, the pressure chamber 31 is expanded from the reference volume and then contracted to the reference volume. Due to the volume change of the series of pressure chambers 31, pressure vibration is generated in the ink in the pressure chamber 31 and the ink in the nozzle 30 communicating with the ink.

  The second vibration drive pulse VP2 corresponds to the first vibration drive pulse in the present invention, and the second potential drops from the reference potential Vb to the second expansion potential VL2 lower than the reference potential Vb and the first expansion potential VL1. It has an expansion component p4, a second expansion hold component p5 that holds the second expansion potential VL2 for a certain period of time, and a second return contraction component p6 that raises the potential from the second expansion potential VL2 to the reference potential Vb. Similar to the first vibration drive pulse VP1, the second vibration drive pulse VP2 drives the piezoelectric element 27 so that the pressure chamber 31 is expanded from the reference volume and then contracted to the reference volume. The drive voltage of the second vibration drive pulse VP2 (potential difference between the reference potential Vb and the second expansion potential VL2) is greater than the drive voltage of the first vibration drive pulse VP1 (potential difference between the reference potential Vb and the first expansion potential VL1). Is also set larger. For this reason, when the piezoelectric element 27 is driven by the second vibration drive pulse VP2, a larger pressure vibration is generated in the ink in the pressure chamber 31 and the ink in the nozzle 30 communicating with the ink.

  The third vibration drive pulse VP3 corresponds to the second vibration drive pulse in the present invention, and includes a first contraction component p7 whose potential increases from the reference potential Vb to a first contraction potential VH1 higher than the reference potential Vb, A first contraction hold component p8 that holds the one contraction potential VH1 for a certain period of time; and a first return expansion component p9 that decreases the potential from the first contraction potential VH1 to the reference potential Vb. When the third vibration drive pulse VP3 is applied to the piezoelectric element 27, the first contraction component p7 causes the piezoelectric element 27 to bend from the reference position corresponding to the reference potential Vb toward the inside of the pressure chamber 31, thereby the pressure chamber. 31 is contracted from the reference volume to the first contraction volume corresponding to the first contraction potential VH1. This contraction state is maintained during the application period of the first contraction hold component p8. Thereafter, the first return expansion component p9 bends from the inside to the outside of the pressure chamber 31 and is displaced to the reference position. Thereby, the pressure chamber 31 expands from the first expansion volume to the reference volume. That is, the pressure chamber 31 is contracted from the reference volume and then expanded to the reference volume. Due to the volume change of the series of pressure chambers 31, pressure vibration is generated in the ink in the pressure chamber 31 and the ink in the nozzle 30 communicating with the ink.

  The fourth vibration drive pulse VP4 corresponds to the second vibration drive pulse in the present invention. The second vibration drive pulse VP4 increases from the reference potential Vb to the second contraction potential VH2 higher than the reference potential Vb and the first contraction potential VH1. It has a contraction component p10, a second contraction hold component p11 that holds the second contraction potential VH2 for a certain period of time, and a second return expansion component p12 that lowers the potential from the second contraction potential VH2 to the reference potential Vb. As with the third vibration drive pulse VP3, the fourth vibration drive pulse VP4 drives the piezoelectric element 27 so that the pressure chamber 31 is contracted from the reference volume and then expanded to the reference volume. The drive voltage (potential difference between the reference potential Vb and the second contraction potential VH2) of the fourth vibration drive pulse VP4 is greater than the drive voltage (potential difference between the reference potential Vb and the first contraction potential VH1) of the third vibration drive pulse VP3. Is also set larger. For this reason, when the piezoelectric element 27 is driven by the fourth vibration drive pulse VP4, a larger pressure vibration is generated in the ink in the pressure chamber 31 and the ink in the nozzle 30 communicating with the ink.

  The printer 1 having the above-described configuration can generate any one of the vibration drive pulses VP1 to VP4 from the drive signal vCOM according to the conditions related to the thickening of the ink or the conditions related to the sedimentation of the components (pigment components and the like) included in the ink. Any one or a plurality of them is selectively applied to the piezoelectric elements 27 corresponding to the respective nozzles 30 to perform a vibration operation. The strength of the vibration operation (strength of the stirring effect) can be arbitrarily changed depending on the number and combination of vibration drive pulses to be selected. As described above, this vibration operation is executed in a state where the nozzle surface of the recording head 6 is capped by the capping mechanism 20 in a standby state where the recording head 6 does not perform the recording operation (printing operation) on the recording medium S. Is done.

  FIG. 5 illustrates a selection pattern of the vibration drive pulse VP in the vibration operation. The first selection pattern shown in FIG. 5A is a pattern in which only the first vibration drive pulse VP1 is selected in the unit period T and applied to the piezoelectric element 27 of the corresponding nozzle 30 to execute the vibration operation. . Regarding the first selection pattern, the effect as a vibration operation, that is, the ink stirring effect is the weakest, but the power consumption in the standby state can be suppressed, and the ink is not stirred more than necessary. The adverse effect on the subsequent ink ejection due to the disturbance of the meniscus in the nozzle 30 is suppressed. As for the first selection pattern, even if only the third vibration drive pulse VP3 is selected instead of the first vibration drive pulse VP1, the same stirring effect can be obtained.

  The second selection pattern shown in FIG. 5B is a pattern in which only the second vibration drive pulse VP2 is selected in the unit period T and applied to the piezoelectric element 27 of the corresponding nozzle 30 to execute the vibration operation. The effect as the vibration operation is stronger than that of the first selection pattern. As for the second selection pattern, even if only the fourth vibration drive pulse VP4 is selected instead of the second vibration drive pulse VP2, the same level of stirring effect can be obtained. Further, in the third selection pattern shown in FIG. 5C, the first vibration driving pulse VP1 and the second vibration driving pulse VP2 are selected in the unit period T, and are sequentially applied to the piezoelectric elements 27 of the corresponding nozzles 30. Thus, the vibration operation is executed and the effect as the vibration operation is stronger than that of the second selection pattern. With respect to the third selection pattern, even if the third vibration driving pulse VP3 and the fourth vibration driving pulse VP4 are selected instead of the first vibration driving pulse VP1 and the second vibration driving pulse VP2, the same stirring effect is obtained. Is obtained.

  In the fourth selection pattern shown in FIG. 5D, the second vibration drive pulse VP2 and the third vibration drive pulse VP3 are selected in the unit period T and sequentially applied to the piezoelectric element 27 of the corresponding nozzle 30 to perform the vibration operation. Is a pattern to be executed. As described above, the pressure chamber 31 is expanded from the reference volume and then returned (contracted) to the reference volume, and the second vibration drive pulse VP2 is contracted from the reference volume and then returned (expanded) to the reference volume. By performing the vibration operation in combination with the third vibration drive pulse VP3, the meniscus can be moved more greatly, and the stirring effect is further enhanced than the above selection patterns. In particular, this is effective for the nozzle 30 that ejects ink containing a component that easily settles.

  As a pattern for combining the vibration drive pulse for expanding the pressure chamber 31 from the reference volume and returning it to the reference volume, and the vibration drive pulse for returning the pressure chamber 31 from the reference volume and returning to the reference volume, a pattern combining VP1 and VP3. A pattern in which VP2 and VP4 are combined, or a pattern in which VP1 and VP4 are combined is conceivable. The stirring effect can be adjusted by combining these patterns. Furthermore, a pattern in which three vibration drive pulses are combined in the unit period T is also conceivable. As described above, the stirring effect can be arbitrarily adjusted by a pattern in which vibration drive pulses are combined. In the fifth selection pattern shown in FIG. 5E, all the vibration drive pulses VP1 to VP4 are selected in the unit period T and sequentially applied to the piezoelectric elements 27 of the corresponding nozzles 30 to execute the vibration operation. The stirring effect is the strongest among the selection patterns illustrated in FIG.

  Next, an example in which a selection pattern is employed according to various conditions relating to thickening of ink or sedimentation of solid components contained in ink will be described. As a condition relating to the thickening of the ink, first, the moisture retention capacity of the ink is considered. Specifically, the degree of progress of thickening varies depending on the moisturizing ability of the ink coloring material (pigment dispersion, etc.) or the amount of the moisturizing agent (organic compound, etc.) added to the ink. Ink having a relatively high moisture retention capacity does not easily increase in viscosity, and therefore, the nozzle 30 or the nozzle row that ejects such ink is vibrated by the first selection pattern or the second pattern. On the other hand, since the viscosity of ink having a relatively low moisturizing capacity is likely to increase, a selection pattern having a higher stirring effect, such as the third selection, is applied to the nozzles 30 or nozzle rows that discharge such ink. The vibration operation is performed according to the pattern or the fourth selection pattern.

  In addition, as a condition related to ink thickening, there is an ink ejection frequency during a recording operation before the nozzle surface of the recording head 6 is capped and enters a standby state. For the nozzle 30 having a relatively high ink ejection frequency, the degree of progress of the ink thickening is relatively low, and hence the vibration operation is performed by the first selection pattern and the second selection pattern. On the other hand, since the degree of progress of ink thickening is relatively high for the nozzle 30 with a relatively low ejection frequency, the vibration operation is performed by the third selection pattern or the fourth selection pattern having a higher stirring effect. .

  Examples of the conditions relating to sedimentation of the solid component contained in the ink include the type of ink, that is, the type of pigment contained in the ink. For example, the pigment ink is more likely to settle the pigment, which is a solid component, than the dye ink. Among pigments, those having a higher specific gravity such as titanium oxide contained in white ink are more likely to settle. For this reason, the nozzle 30 or the nozzle row that discharges ink that is unlikely to cause sedimentation of solid components, such as dye ink, is vibrated by the third selection pattern or the fourth selection pattern having a higher stirring effect. Done. In addition, regarding ink containing flat particles having a flat shape such as a metal foil, the ejection of the ink may become unstable when agitated. Therefore, the nozzle 30 or the nozzle array for ejecting such ink may be used. On the other hand, the vibration operation is performed by the first selection pattern having the weakest stirring effect or the vibration operation is not performed.

  Furthermore, even if the nozzles 30 belong to the same nozzle row in the recording head 6, there are cases where the nozzles 30 that are difficult to increase in viscosity and the nozzles 30 that are likely to increase in viscosity coexist for structural reasons. Specifically, the nozzle 30 positioned at the end of the nozzle row is more likely to increase the viscosity of the ink than the nozzle 30 positioned at the center of the nozzle row. For this reason, the vibration operation is performed by the first selection pattern for the nozzles 30 located in the center of the nozzle row, and the nozzle 30 located at the end of the nozzle row is selected with a higher stirring effect. The vibration operation is performed by a pattern, for example, the second selection pattern or the third selection pattern. For example, the nozzle 30 or the nozzle row that discharges ink that has a low moisture retention ability and that is likely to cause precipitation of the pigment, and has a long elapsed time from the previous discharge, has the highest stirring effect. The vibration operation is performed according to the fifth selection pattern. As a result, it is possible to reduce ejection defects due to ink thickening or pigment settling when the next recording operation is started.

As described above, one or more of the vibration drive pulses in the drive signal vCOM are selectively applied to the piezoelectric element 27 in accordance with various conditions relating to ink thickening or sedimentation of components contained in the ink. By executing the vibration operation, it is possible to execute a more appropriate vibration operation without excess or deficiency in accordance with the degree of thickening of the ink or the degree of sedimentation of the solid component.
In addition, as in the illustrated drive signal vCOM, a plurality of first vibration drive pulses VP1 and VP2 having different voltages and a plurality of second vibration drive pulses VP3 and VP4 having different voltages are included in a unit period T. By adopting such a configuration, the range of selection of the vibration drive pulse is widened, and it becomes possible to more efficiently execute the vibration operation by combining these.

  The number and order of the vibration drive pulses included in the drive signal are not limited to those illustrated. The point is that the first vibration driving pulse that raises the potential from the reference potential that becomes the reference of the potential change and then raises the potential to the reference potential, and the first vibration drive pulse that raises the potential from the reference potential and then lowers the potential to the reference potential. Any configuration may be used as long as at least one vibration drive pulse is generated within the unit period T which is a repetition period.

  In the above-described embodiment, the so-called flexural vibration type piezoelectric element 27 is exemplified as the piezoelectric element. However, the piezoelectric element is not limited to this, and for example, a so-called longitudinal vibration type piezoelectric element can be employed. In addition, the actuator is not limited to the piezoelectric element as long as it is an actuator that causes pressure vibration in the liquid in the pressure chamber. For example, a heating element, an electrostatic actuator, or the like can be employed.

  The present invention is not limited to a printer, as long as it is a liquid ejection apparatus that drives an actuator by applying a vibration drive pulse to control liquid vibration, and various ink jet recording apparatuses such as a plotter, a facsimile machine, and a copier. It can also be applied to.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 6 ... Recording head, 9 ... CPU, 11 ... Drive signal generation circuit, 20 ... Capping mechanism, 27 ... Piezoelectric element, 30 ... Nozzle, 31 ... Pressure chamber

Claims (2)

A liquid ejection head having a nozzle surface on which nozzles for ejecting liquid are formed, and an actuator for generating pressure vibration in the liquid in the pressure chamber communicating with the nozzle;
A drive signal generation circuit that periodically generates a drive signal including a vibration drive pulse that drives the actuator to cause the liquid in the pressure chamber to vibrate and cause the liquid to vibrate;
A capping mechanism for sealing the nozzle surface of the liquid discharge head;
A control circuit for controlling the vibration operation by applying the vibration drive pulse to the actuator in a state where the nozzle surface of the liquid discharge head is sealed by the capping mechanism;
With
The drive signal includes a first vibration drive pulse that lowers the potential from a reference potential that is a reference for potential change and then increases the potential to the reference potential, and increases the potential from the reference potential to the reference potential. Generating at least one second vibration drive pulse for lowering the potential within a repetition period;
The control circuit may select either the first vibration drive pulse or the second vibration drive pulse from the drive signal according to a condition related to liquid thickening or a condition related to sedimentation of components contained in the liquid. A liquid ejection apparatus, wherein one or more are selectively applied to the actuator to execute the vibration operation.   2. The drive signal according to claim 1, wherein a plurality of first vibration drive pulses having different voltages and a plurality of second vibration drive pulses having different voltages are generated within a repetition period. Liquid ejection device.

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