阅读说明：本技术 液体喷出装置的致动器驱动电路及印刷控制装置
(Actuator drive circuit for liquid ejecting apparatus and print control apparatus
) 是由 仁田昇
小野俊一
原田苍太 于 2020-03-05 设计创作，主要内容包括：本发明提供液体喷出装置的致动器驱动电路及印刷控制装置,能够停止施加偏置电压,而且接下来喷出液体时致动器的特性稳定。实施方式的液体喷出装置的致动器驱动电路具备喷出波形生成部、睡眠波形生成部以及唤醒波形生成部。喷出波形生成部接收由多个比特构成的灰度数据,并根据该灰度数据的灰度值向致动器赋予喷出液体的驱动电压波形。睡眠波形生成部不喷出液体并使致动器的电压转变为第一电压。唤醒波形生成部不喷出液体并使致动器的电压转变为比第一电压大的第二电压。(The invention provides an actuator drive circuit of a liquid ejecting apparatus and a printing control apparatus, which can stop applying a bias voltage and stabilize the characteristics of an actuator when ejecting liquid next. An actuator driving circuit of a liquid ejecting apparatus according to an embodiment includes an ejection waveform generating unit, a sleep waveform generating unit, and a wake-up waveform generating unit. The discharge waveform generating unit receives gradation data composed of a plurality of bits, and applies a drive voltage waveform for discharging the liquid to the actuator according to a gradation value of the gradation data. The sleep waveform generation unit does not eject the liquid and converts the voltage of the actuator to a first voltage. The wake-up waveform generating unit converts the voltage of the actuator to a second voltage that is higher than the first voltage without ejecting the liquid.)
1. An actuator driving circuit of a liquid discharge apparatus, comprising:
a discharge waveform generating unit that receives gradation data composed of a plurality of bits and applies a drive voltage waveform for discharging liquid to an actuator according to a gradation value of the gradation data;
a sleep waveform generating unit that converts the voltage of the actuator to a first voltage without ejecting liquid; and
and a wake-up waveform generating unit that converts the voltage of the actuator to a second voltage that is greater than the first voltage without discharging the liquid.
2. The actuator driving circuit of a liquid ejection device according to claim 1,
when a first instruction for activating the sleep waveform generating section is allocated to a part of a plurality of bits constituting the gradation data and the first instruction is extracted, a sleep waveform is given to the actuator.
3. The actuator driving circuit of a liquid ejection device according to claim 1 or 2,
when a second command for activating the wake-up waveform generating section is allocated to a part of a plurality of bits constituting the gradation data and the second command is extracted, a wake-up waveform is given to the actuator.
4. The actuator driving circuit of a liquid ejection device according to claim 1 or 2,
when a third instruction to hold the voltage applied to the actuator as the first voltage is allocated to a part of a plurality of bits constituting the gradation data and the third instruction is extracted, the voltage applied to the actuator is held as the first voltage.
5. The actuator driving circuit of a liquid ejection device according to claim 3,
when a third instruction to hold the voltage applied to the actuator as the first voltage is allocated to a part of a plurality of bits constituting the gradation data and the third instruction is extracted, the voltage applied to the actuator is held as the first voltage.
6. The actuator driving circuit of a liquid ejection device according to claim 1 or 2,
the first voltage is a low voltage that is low to an extent that does not cause the actuator to change over time.
7. The actuator driving circuit of a liquid ejection device according to claim 1 or 2,
the second voltage is the same as an initial voltage and/or an end voltage of a drive voltage waveform for ejecting the liquid.
8. The actuator driving circuit of a liquid ejection device according to claim 1 or 2,
the sleep waveform generation unit generates an encoded drive voltage waveform corresponding to sleep without using a frame.
9. The actuator driving circuit of a liquid ejection device according to claim 1 or 2,
the wake-up waveform generator generates an encoded drive voltage waveform corresponding to wake-up without using a frame.
10. A printing control apparatus is characterized in that,
when detecting that the liquid is not continuously ejected, sending a first instruction for giving a sleep waveform to the actuator drive circuit;
upon detecting a restart of ejection of the liquid, a second instruction for giving a wake-up waveform to the actuator is sent to the actuator drive circuit before the restart of ejection.
Technical Field
Embodiments of the present invention relate to an actuator driving circuit of a liquid ejecting apparatus and a printing control apparatus.
Background
A liquid ejecting apparatus is known which supplies a predetermined amount of liquid to a predetermined position. The liquid discharge device is mounted on, for example, an inkjet printer, a 3D printer, a dispensing device, and the like. An inkjet printer ejects droplets of ink from an inkjet head to print an image or the like on a surface of a recording medium. The 3D printer ejects droplets of modeling material from the modeling material ejection head and solidifies the droplets, thereby forming a three-dimensional modeled object. The dispensing device discharges droplets of a sample and supplies the droplets to a plurality of containers or the like by a predetermined amount.
An inkjet head, which is a liquid discharge device of an inkjet printer, includes a piezoelectric actuator as a driving device for discharging ink from nozzles. A set of nozzles and actuators form a channel. The head drive circuit applies a drive voltage waveform to an actuator selected based on print data to drive the actuator. For example, it is proposed to stop applying the bias voltage when printing is not performed, so as to suppress deterioration of the actuator. For example, the following manner: the print data is latched by a buffer of 3 stages, and the application of the bias voltage is stopped when the next dot is blank. However, in this method, whether or not to stop applying the bias voltage and whether or not to start applying the bias voltage are determined based on the history of presence or absence of printing in the 3-stage buffer, and therefore, the application time of the bias voltage before printing cannot be freely adjusted. Therefore, after the bias voltage is applied, it is impossible to cope with a phenomenon in which the characteristics of the actuator change in a short period of time, thereby causing a reduction in print quality.
Disclosure of Invention
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an actuator driving circuit and a print control device for a liquid discharge apparatus, which can stop application of a bias voltage to an actuator and stabilize the characteristics of the actuator when a liquid is discharged next.
An actuator driving circuit of a liquid ejecting apparatus according to an embodiment of the present invention includes an ejection waveform generating unit, a sleep waveform generating unit, and a wake-up waveform generating unit. The discharge waveform generating unit receives gradation data composed of a plurality of bits, and applies a drive voltage waveform for discharging the liquid to the actuator according to a gradation value of the gradation data. The sleep waveform generation unit does not eject the liquid and converts the voltage of the actuator to a first voltage. The wake-up waveform generating unit converts the voltage of the actuator to a second voltage that is higher than the first voltage without ejecting the liquid.
A print control apparatus according to another embodiment of the present invention, when detecting that liquid is not continuously ejected, transmits a first command for giving a sleep waveform to an actuator drive circuit; upon detecting a restart of ejection of the liquid, a second instruction for giving a wake-up waveform to the actuator is sent to the actuator drive circuit before the restart of ejection.
Drawings
Fig. 1 is an overall configuration diagram of an inkjet printer according to an embodiment.
Fig. 2 is a perspective view of the ink jet head of the ink jet printer.
Fig. 3 is a plan view of a nozzle plate of the ink jet head.
Fig. 4 is a longitudinal sectional view of the ink jet head.
Fig. 5 is a longitudinal sectional view of a nozzle plate of the ink jet head.
Fig. 6 is a block diagram showing the configuration of the control system of the ink jet printer.
Fig. 7 is a block diagram showing the configuration of the command analysis unit of the control system.
Fig. 8 is a block diagram showing the configuration of the waveform generating unit of the control system.
Fig. 9 is an explanatory diagram of a WG register showing information of a drive voltage waveform for one frame.
Fig. 10 is an explanatory diagram of the WG register allocation and encoding drive voltage waveforms WK0 to WK7 for each gray scale value.
Fig. 11 is a block diagram showing the configuration of the waveform selecting unit of the control system.
Fig. 12 is a circuit diagram of an output buffer of the above-described control system.
Fig. 13 shows an example of a series of drive voltage waveforms applied to the inkjet head.
Fig. 14 is an explanatory diagram showing a phenomenon of print deepening at the first dot after the application of the bias voltage is stopped.
Fig. 15 is an explanatory diagram showing a test drive voltage waveform and a measurement result of the electrostatic capacitance of the actuator performed to confirm the phenomenon of the print deepening at the first dot.
Fig. 16 shows another example of a series of driving voltage waveforms applied to the ink jet head.
Fig. 17 is an explanatory diagram showing a modification of WG registers GW and GS.
Fig. 18 is an explanatory diagram showing a modification of WG registers GW and GS.
Fig. 19 is an explanatory diagram of the WG register allocation and encoding drive voltage waveforms WK0 to WK7 for each gray scale value.
Fig. 20 shows another example of a series of driving voltage waveforms applied to the ink jet head.
Description of the reference numerals
10: an ink jet printer; 1A to 1D: an ink jet head; 4: an ink supply section; 51: a nozzle; 7: a head drive circuit; 72: an instruction analysis unit; 74: a print data buffer; 75: a waveform selection unit; 76: an output buffer; 8: an actuator; 100: a printing control device; 307: a WG register storage section; 400: a WGG register; q0: a first transistor; q1: a second transistor; q2: a third transistor.
Detailed Description
Next, an actuator driving circuit of a liquid ejecting apparatus according to an embodiment will be described in detail with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals.
An ink jet printer 10 that prints an image on a recording medium will be described as an example of an image forming apparatus having the liquid discharge apparatus 1 of the embodiment. Fig. 1 shows a schematic configuration of an inkjet printer 10. The inkjet printer 10 includes, for example, a box-shaped housing 11 as an external component. Inside the housing 11 are disposed: a cassette 12 that stores a sheet S as an example of a recording medium, an upstream conveyance path 13 of the sheet S, a conveyance belt 14 that conveys the sheet S taken out from the cassette 12, inkjet heads 1A to 1D that eject droplets of ink toward the sheet S on the conveyance belt 14, a downstream conveyance path 15 of the sheet S, a discharge tray 16, and a control board 17. An operation unit 18 as a user interface is disposed on the upper side of the housing 11.
The image data printed on the sheet S is generated by, for example, the computer 2 as an externally connected device. The image data generated by the computer 2 is transmitted to the control board 17 of the inkjet printer 10 via the cable 21 and the connectors 22B and 22A.
The pickup roller 23 feeds the sheets S one by one from the cassette 12 to the upstream conveying path 13. The upstream conveying path 13 is constituted by the pair of feed rollers 13a, 13b and the sheet guide plates 13c, 13 d. The sheet S is conveyed onto the upper surface of the conveying belt 14 via the upstream conveying path 13. An arrow a1in the figure indicates a conveying path of the sheet S from the cassette 12 to the conveying belt 14.
The conveyor belt 14 is a mesh-like endless belt having a large number of through holes formed on the surface thereof. The conveyor belt 14 is rotatably supported by three rollers, i.e., a drive roller 14a and driven rollers 14b and 14 c. The motor 24 rotates the conveying belt 14 by rotating the driving roller 14 a. The motor 24 is an example of a driving device. In the figure, a2 indicates the rotation direction of the conveyor belt 14. A negative pressure container 25 is disposed on the back side of the conveyor belt 14. The negative pressure container 25 is connected to a fan 26 for pressure reduction, and the inside of the container is made negative by an air flow generated by the fan 26. The sheet S is subjected to negative pressure in the negative pressure container 25 and is sucked and held on the upper surface of the conveying belt 14. In the figure, a3 represents the flow direction of the air flow.
The inkjet heads 1A to 1D are disposed so as to face the sheet S sucked and held on the conveying belt 14 with a minute gap of, for example, 1 mm. The inkjet heads 1A to 1D respectively eject droplets of ink toward the sheet S. The sheet S is printed with an image while passing under the inkjet heads 1A to 1D. The ink jet heads 1A to 1D have the same configuration except that the colors of the discharged inks are different. The color of the ink is, for example, cyan, magenta, yellow, and black.
The ink jet heads 1A to 1D are connected to the ink cartridges 3A to 3D and the ink supply pressure adjusting devices 32A to 32D via the ink flow paths 31A to 31D, respectively. The ink flow paths 31A to 31D are, for example, resin tubes. The ink cartridges 3A to 3D are containers for storing ink. The ink cartridges 3A to 3D are disposed above the ink jet heads 1A to 1D. During standby, the ink supply pressure adjusting devices 32A to 32D adjust the pressure inside the inkjet heads 1A to 1D to a negative pressure, for example, -1kPa, with respect to the atmospheric pressure, so as to prevent ink from leaking from the nozzles 51 (see fig. 2) of the inkjet heads 1A to 1D. When printing an image, the inks of the respective ink cartridges 3A to 3D are supplied to the respective ink jet heads 1A to 1D by the ink supply pressure adjusting devices 32A to 32D.
After printing, the sheet S is conveyed from the conveying belt 14 to the downstream conveying path 15. The downstream conveying path 15 is constituted by a pair of feed rollers 15a, 15b, 15c, 15d and sheet guide plates 15e, 15f that define a conveying path of the sheet S. The sheet S is conveyed from the discharge port 27 to the discharge tray 16 via the downstream conveying path 15. An arrow a4 in the figure indicates a conveying path of the sheet S.
Next, the structure of the ink jet head 1A as a liquid ejection head will be described with reference to fig. 2 to 6. The ink jet heads 1B to 1D have the same configuration as the ink jet head 1A, and therefore, detailed description thereof is omitted.
Fig. 2 is an external perspective view of the ink-jet head 1A. The ink jet head 1A includes: the ink supply unit 4, the nozzle plate 5, the flexible substrate 6, and the head drive circuit 7 are examples of liquid supply units. A plurality of nozzles 51 for ejecting ink are arranged on the nozzle plate 5. The ink discharged from each nozzle 51 is supplied from the ink supply portion 4 communicating with the nozzle 51. The ink flow path 31A from the ink supply pressure adjusting device 32A is connected to the upper side of the ink supply unit 4. The arrow a2 indicates the rotation direction of the conveyor belt 14 (see fig. 1).
Fig. 3 is a partially enlarged top view of the nozzle plate 5. The nozzles 51 are two-dimensionally arranged in a column direction (X direction) and a row direction (Y direction). However, the nozzles 51 arranged in the row direction (Y direction) are arranged obliquely so that the nozzles 51 do not overlap on the axis of the Y axis. The nozzles 51 are arranged at intervals of a distance X1 in the X-axis direction and at intervals of a distance Y1 in the Y-axis direction. For example, the distance X1 is approximately 42.25 μm, and the distance Y1 is approximately 253.5 μm. That is, the distance X1 is determined in the X-axis direction so that the recording density of 600DPI is achieved. Further, the distance Y1 was also determined in the Y axis direction so that printing was performed at 600 DPI. The nozzles 51 are arranged in a plurality of groups in the X direction with eight nozzles 51 arranged in the Y direction as one group. Although not shown, for example, 150 sets of nozzles 51 are arranged in the X direction, and a total of 1200 nozzles are arranged.
Each nozzle 51 is provided with a piezoelectric-driven electrostatic capacitive actuator 8 (hereinafter, simply referred to as "actuator 8") as a driving source for ink discharge operation. A set of nozzles 51 and actuators 8 form a channel. The actuators 8 are formed in a circular ring shape and arranged so that the nozzle 51 is positioned at the center thereof. The dimensions of the actuator 8 are, for example, an inner diameter of 30 μm and an outer diameter of 140 μm. Each actuator 8 is electrically connected to the individual electrode 81. Further, the eight actuators 8 arranged in the Y direction are electrically connected to each other by the common electrode 82 of each actuator 8. The individual electrodes 81 and the common electrodes 82 are also electrically connected to the mounting pads 9, respectively. The mounting pad 9 becomes an input port for applying a drive voltage waveform to the actuator 8. The individual electrodes 81 apply drive voltage waveforms to the actuators 8, and the actuators 8 are driven according to the applied drive voltage waveforms. In fig. 3, for convenience of explanation, the actuator 8, the individual electrode 81, the common electrode 82, and the mounting pad 9 are illustrated by solid lines, but they are disposed inside the nozzle plate 5 (see the vertical cross-sectional view of fig. 4). Of course, the position of the actuator 8 is not limited to the inside of the nozzle plate 5.
The mounting pads 9 are electrically connected to wiring patterns formed on the flexible substrate 6 by, for example, Anisotropic Conductive Film (ACF). The wiring pattern of the flexible substrate 6 is electrically connected to the head drive circuit 7. The head drive Circuit 7 is, for example, an IC (Integrated Circuit). The head drive circuit 7 applies a drive voltage waveform to the actuator 8 selected based on the image data to be printed.
Fig. 4 is a longitudinal sectional view of the ink-jet head 1A. As shown in fig. 4, the nozzle 51 penetrates the nozzle plate 5 in the Z-axis direction. The nozzle 51 has a diameter of 20 μm and a length of 8 μm, for example. The ink supply portion 4 is provided therein with a plurality of pressure chambers (independent pressure chambers) 41 that communicate with the respective nozzles 51. The pressure chamber 41 is, for example, a cylindrical space whose upper portion is open. The upper portion of each pressure chamber 41 is open and communicates with the common ink chamber 42. The ink flow path 31A communicates with the common ink chamber 42 via the ink supply port 43. The pressure chambers 41 and the common ink chamber 42 are filled with ink. The common ink chamber 42 may be formed in a flow path shape for circulating ink, for example. The pressure chamber 41 has a structure in which, for example, a cylindrical hole having a diameter of, for example, 200 μm is formed in a single crystal silicon wafer having a thickness of, for example, 500 μm. The ink supply portion 4 is made of, for example, alumina (Al)2O3) And a space corresponding to the common ink chamber 42 is formed.
FIG. 5 shows a nozzle plate 5A partially enlarged view of (a). The nozzle plate 5 has a structure in which a protective layer 52, an actuator 8, and a diaphragm 53 are stacked in this order from the bottom surface side. The actuator 8 has a structure in which a lower electrode 84, a piezoelectric body 85 which is a thin film as an example of a piezoelectric element, and an upper electrode 86 are stacked. The upper electrode 86 is electrically connected to the individual electrode 81, and the lower electrode 84 is electrically connected to the common electrode 82. An insulating layer 54 for preventing short-circuiting between the individual electrode 81 and the common electrode 82 is interposed between the protective layer 52 and the diaphragm 53. The insulating layer 54 is made of, for example, a silicon dioxide film (SiO) having a thickness of 0.5 μm2) And (4) forming. The lower electrode 84 and the common electrode 82 are electrically connected through a contact hole 55 formed in the insulating layer 54. The piezoelectric body 85 is formed of, for example, PZT (lead zirconate titanate) having a thickness of 5 μm or less in consideration of piezoelectric characteristics and insulation breakdown voltage. The upper electrode 86 and the lower electrode 84 are formed of, for example, platinum having a thickness of 0.15 μm. The individual electrodes 81 and the common electrode 82 are formed of, for example, gold (Au) having a thickness of 0.3 μm.
The vibration plate 53 is formed of an insulating inorganic material. The insulating inorganic material is, for example, silicon dioxide (SiO)2). The thickness of the diaphragm 53 is, for example, 2 μm to 10 μm, preferably 4 μm to 6 μm. D generation of the diaphragm 53 and the protective layer 52 by the piezoelectric body 85 to which a voltage is applied31The pattern deforms to bend inward. Then, when the voltage application to the piezoelectric body 85 is stopped, the state is restored. The reversible deformation causes the volume of the pressure chamber (independent pressure chamber) 41 to expand and contract. When the volume of the pressure chamber 41 changes, the ink pressure in the pressure chamber 41 changes. The ink is ejected from the nozzle 51 by the expansion and contraction of the volume of the pressure chamber 41 and the change in ink pressure. That is, the nozzle 51 and the actuator 8 constitute an example of the liquid ejecting section.
The protective layer 52 is formed of, for example, polyimide having a thickness of 4 μm. The protective layer 52 covers one surface of the bottom surface of the nozzle plate 5, and further covers the inner peripheral surface of the hole of the nozzle 51.
Fig. 6 is a block diagram of the configuration of the control system of the inkjet printer 10. The control system of the inkjet printer 10 is constituted by a print control device 100 as a control unit of the printer and a head drive circuit 7. The head drive circuit 7 is an example of an actuator drive circuit. The print control apparatus 100 includes a CPU101, a storage unit 102, an image memory 103, a head interface 104, and a conveyance interface 105. The print control device 100 is mounted on the control board 17, for example. The storage unit 102 is, for example, a ROM, and the image memory 103 is, for example, a RAM. The image data from the computer 2 as an external connection device is transmitted to the print control apparatus 100 and stored in the image memory 103. The CPU101 reads image data from the image memory 103, converts the image data into a format conforming to the data format of the ink-jet heads 1A to 1D, and transmits the converted image data to the head interface 104 as print data. The print data is an example of liquid ejection data. The head interface 104 sends print data and other control instructions to the head drive circuit 7. Although not shown, the head driving circuits 7 of the other ink jet heads 1B to 1D have the same circuit configuration.
The conveyance interface 105 controls the conveyance device 106 (the conveyance belt 14, the drive motor 24, and the like) to convey the sheet S in accordance with instructions from the CPU101, detects the relative positions of the sheet S and the inkjet heads 1A to 1D by a position sensor (not shown) such as an optical encoder, and transmits the timing at which each nozzle 51 is to eject ink to the head interface 104. The head interface 104 transmits the ejection timing to the head drive circuit 7 as a print trigger. The print trigger is one of control instructions sent to the head drive circuit 7.
In the head drive circuit 7, a voltage V0 as a first voltage, a voltage V1 as a second voltage, and a voltage V2 as a third voltage are applied as actuator power sources. For example, the voltage V1 is a dc voltage of 30V, the voltage V2 is a dc voltage of 10V, and the voltage V0 is a dc voltage of 0V (V1 > V2 > V0). The magnitudes of the voltages V1 and V2 are adjusted stepwise by a power supply circuit, not shown, in accordance with, for example, the viscosity and temperature of the ink.
The head drive circuit 7 includes a receiving unit 71, a command analyzing unit 72, a waveform generating unit 73, a print data buffer 74, a waveform selecting unit 75, and an output buffer 76. The output buffer 76 is an example of an output switch. The receiving unit 71 receives data from the print control apparatus 100 and transmits the data to the command analyzing unit 72. The command analysis unit 72 analyzes the received data. Specifically, as shown in fig. 7, the command analysis unit 72 includes a waveform setting information extraction unit 200, a print trigger extraction unit 201, a Sleep (Sleep) command extraction unit 202, a Wake (Wake) command extraction unit 203, a print data extraction unit 204, and a print data output unit 205. The command analysis unit 72 analyzes whether or not the received data is waveform setting information, a print trigger, a wakeup command, a sleep command, or print data, and extracts the data. Of course, other instructions than these are possible. The data from the print control apparatus 100 transmits these information and commands in units of packets. There are also cases where a plurality of instructions are contained in one packet.
After the analysis, the waveform setting information is sent to the waveform generating unit 73. The print trigger is sent to both the waveform generation section 73 and the print data buffer 74. The print trigger sent to the waveform generating section 73 becomes a start signal for executing waveform generation. The print trigger sent to the print data buffer 74 becomes a buffer update signal for transferring data from the input side to the output side in the print data buffer 74. The print data, the wakeup command, and the sleep command are transmitted to the print data output unit 205.
Upon receiving the print data from the print data extraction unit 204, the print data output unit 205 sends the data to the print data buffer 74. The print data is, for example, gradation data of a plurality of bits. The gradation data indicates, for example, whether or not ejection is performed, an ejection amount during ejection, and other operations, by gradation values of 0 to 7. For example, a gray value of 0 is the application of the sustain bias voltage, a gray value of 1 is the one-drop ink, a gray value of 2 is the two-drop ink, a gray value of 3 is the three-drop ink, a gray value of 4 is the four-drop ink, a gray value of 5 is awake, a gray value of 6 is Sleep, and a gray value of 7 is Sleep-sustain (Sleep hold). In the case where the printing control apparatus 100 is a multi-nozzle head including a plurality of channels each formed by a combination of the nozzle 51 and the actuator 8, gradation values of 0 to 7 are assigned to the respective channels.
On the other hand, when receiving the wake-up command from the wake-up command extracting unit 203, the print data output unit 205 transmits the gradation value 5 defined as the wake-up data to all the actuators 8 (uniform wake-up). In addition, upon receiving the sleep command from the sleep command extracting section 202, the print data output section 205 transmits the gradation value 6 defined as the sleep data to all the actuators 8 (sleep uniformly). That is, an awake command is assigned to a gradation value 5 which is one of gradation values 0 to 7 as gradation data, and a sleep command is assigned to a gradation value 6. Likewise, a Sleep hold (Sleep hold) is assigned to the gray value 7.
That is, as a method of transmitting the wakeup data to the print data buffer 74, two methods, that is, a method of transmitting the encoded print data and a method of transmitting the wakeup command, are prepared. The former can wake up only a specified actuator 8, and the latter can wake up all actuators 8 uniformly. Similarly, as a method of transmitting sleep data to the print data buffer 74, two methods, that is, a method of transmitting encoded print data and a method of transmitting sleep command, are prepared. The former can sleep only the designated actuators 8, and the latter can sleep all the actuators 8 collectively.
Next, as shown in fig. 8, the waveform generation unit 73 includes waveform generation circuits 300 to 306 and a WG register storage unit 307. The waveform generation circuits 300 to 306 and the WG register storage part 307 use WG registers indicating information of drive voltage waveforms of 1 frame to generate encoded drive voltage waveforms WK0 to WK7 corresponding to respective gradation values 0 to 7. The information of the drive voltage waveform for 1 frame worth is represented by, for example, a status value and a timer value.
Waveform generation circuits 300 to 304 corresponding to gradation values 0 to 4 among gradation values 0 to 7 allocate a plurality of types of WG registers representing different types of drive voltage waveforms to four frames F0 to F3 arranged in time series, thereby generating encoded drive voltage waveforms WK0 to WK4 corresponding to gradation values 0 to 4. The waveform generation circuits 300 to 304 are examples of a discharge waveform generation section which provides a drive voltage waveform for discharging ink to the actuator 8. The waveform generation circuit 300 corresponding to the gradation value 0 includes a WGG register 400, a frame counter 401, a selector 402, a selector 403, a state machine 404, and a timer 405. Although only the circuit configuration of the waveform generation circuit 300 is shown, the waveform generation circuits 301 to 304 have the same circuit configuration. The WGG register 400 sets which of a plurality of WG registers is allocated to the four frames F0 to F3. That is, the WGG register 400 is a waveform setting unit that sets a drive voltage waveform used for each gradation value. Which WG register is allocated to each of the four frames F0 to F3 of the WGG register 400 differs depending on the gradation value. That is, the WGG register 400 and the WG register 307 as the waveform setting unit are examples of a waveform memory configured to store a plurality of sets of drive voltage waveforms and holding voltages to be described later.
The frame counter 401 selects frames in the order of F0, F1, F2, and F3. The selector 402 selects the WG register allocated to the frame selected by the frame counter 401 according to the setting of the WGG register 400. The selector 403 sets the values of the state machine 404 and the timer 405 according to the state value of the selected WG register and the timer value. The state value and the timer value of each WG register are received from the WG register storage unit 307. The timer 405 counts the set time, and the state machine 404 updates the state when the time of the timer 405 ends.
The waveform generation circuits 305 and 306 for the gradation value 5 corresponding to the wake-up data and the gradation value 6 corresponding to the sleep data include state machines 406 and 408 and timers 407 and 409. Unlike the gradation values 0 to 4, the waveform generation circuits 305 and 306 generate the encoded drive voltage waveforms WK5 and WK6 corresponding to wake-up and sleep, respectively, without using a frame. The encoded drive voltage waveform WK7 is generated similarly for the gradation value 7 corresponding to the sleep maintenance data without using a frame. The waveform generation circuit 305 is an example of a wake-up waveform generation unit that does not discharge ink and converts the voltage of the actuator 8 to the voltage V1, and the waveform generation circuit 306 is an example of a sleep waveform generation unit that does not discharge ink and converts the voltage of the actuator 8 to the voltage V0.
The WG register storage unit 307 stores a plurality of WG registers. Fig. 9 shows an example of the WG register and its setting value. In this example, five kinds of WG registers GW, GS, G0, G1, G2 are used. Each GW register indicates information of a drive voltage waveform for 1 frame by nine state values of S0 to S8 and eight timer values of t0 to t7, which are settings of the time of execution state. The state values are, for example, 0, 1, 2, and 3. The state value 0 means that a first output switch that applies the voltage V0 as the first voltage to the actuator 8 is turned ON (ON), the state value 1 means that a second output switch that applies the voltage V1 as the second voltage to the actuator 8 is turned ON, and the state value 2 means that a third output switch that applies the voltage V2 as the third voltage to the actuator 8 is turned ON. The state value 3 is to turn OFF all the first to third output switches (OFF) and to make the output of the driving circuit high impedance. Each output switch is, for example, a transistor (see fig. 12).
During the state holding time t0 of the state S0, it then becomes the state S1. During the state holding time t1 of the state S1, it then becomes the state S2. During the state holding time t2 of the state S2, it then becomes the state S3. During the state holding time t3 of the state S3, it then becomes the state S4. During the state holding time t4 of the state S4, it then becomes the state S5. During the state holding time t5 of the state S5, it then becomes the state S6. During the state holding time t6 of the state S6, it then becomes the state S7. During the state holding time t7 of the state S7, it then becomes the state S8. State S8 has no hold time. The state of state S8 is updated to the next frame or held until the next occurrence of a print trigger. That is, the voltage set in the last state S8 is the holding voltage. When the first to third transistors Q0, Q1, and Q2, which will be described later, are used for the output buffer 76, the ON/OFF (ON/OFF) state to be held is determined. That is, the WG register storage 307, which is an example of a waveform memory, stores information on a plurality of types of drive voltage waveforms that differ from each other in the transistor that is turned on last. Of course, the coded drive voltage waveforms WK0 through WK6 themselves may be stored in the waveform memory.
The state values and timer values of the WG registers GW, GS, G0, G1, and G2 are transmitted from the WG register storage unit 307 to the waveform generation circuits 300 to 306 that generate the encoded drive voltage waveforms WK0 to WK 6. The waveform generation circuits 300 to 306 generate encoded drive voltage waveforms WK0 to WK6 based on the state values of the WG registers and the timer values. WK7 is in the final state of GS S8. The trigger to start generating the encoded drive voltage waveforms WK0 to WK7 is a print trigger. For example, when a print trigger signal is input, the waveform generation circuits 300 to 304 corresponding to the tone values 0 to 4 read the corresponding state values of the WG register and the timer value in accordance with the setting of the WGG register 400, output the corresponding state values to the encoded drive voltage waveforms WK0 to WK4 for the time of the timer value, and repeat the processing for all the frames F0 to F4.
Fig. 10 shows encoded drive voltage waveforms WK0 to WK7 generated and assigned to WG registers GW, GS, G0, G1, and G2 for respective gradation values of 0 to 7. As shown in fig. 10, in the encoded drive voltage waveform WK0 corresponding to the gradation value 0, the value of the WG register G0 is output for the periods F0 to F3, and the final value is held. All the state values of G0 are "1", and therefore, the voltage V1 is output during this period. In the encoded drive voltage waveform WK1 corresponding to the gradation value 1 of one-drop ink, the value of the WG register G1 is output during F0, and the value of G0 is output during F1 to F3, and the final value is held. In the encoded drive voltage waveform WK2 corresponding to the gradation value 2 of the twice-dropped ink, the value of the WG register G1 is repeatedly output for periods F0 to F1, and the value of G0 is output for periods F2 to F3, and the final value is held. In the encoded drive voltage waveform WK3 corresponding to the gradation value 3 of the three-drop ink, the value of the WG register G1 is repeatedly output during periods F0 to F2, and the value of G0 is output during period F3, and the final value is held. In the encoded drive voltage waveform WK4 corresponding to the gradation value 4 of four drops of ink, the value of the WG register G1 is repeatedly output for the periods F0 to F3, and the value of G2 is output at the end of F3 (state S8), and the final value is held. The state of state S8 remains until, for example, the next occurrence of a print trigger. That is, the voltage set in the last state S8 is the holding voltage after the drive voltage waveform is applied. The holding voltage can be set and changed from the printing control apparatus 100, for example.
The gray- scale values 5, 6, and 7 do not use a frame and the WGG register 400 is not set, and the waveform generation operation is different from the gray-scale values 0 to 4. The value of the WG register GW is output to the encoded drive voltage waveform WK5 corresponding to the gradation value 5, and the final value is held. The value of the WG register GS is output to the encoded drive voltage waveform WK6 corresponding to the gradation value 6, and the final value is held. The value of the state S8 of the WG register GS is output to and held in the encoded drive voltage waveform WK7 corresponding to the gradation value 7. The state of state S8 remains until, for example, the next occurrence of a print trigger. The encoded drive voltage waveforms WK0 to WK7 thus generated are applied to the selected inputs of the waveform selection units 75, respectively. In this example, the setting values transmitted from the print control apparatus 100 by the waveform setting information command are set in the WG register and the WGG register 400. Of course, the setting values of the WG register and the WGG register 400 may be fixed values, but setting from the print control apparatus 100 is possible, which has the following advantages.
That is, the inkjet heads 1A to 1D do not have detailed information about the ink. This is because how to change the drive voltage waveform when the ink changes or when the temperature of the ink changes is not general, and if the detailed information on the ink is fixed in the individual inkjet heads 1A to 1D, it is not possible to cope with, for example, a new ink or a new required drive condition. The ink jet heads 1A to 1D alone generally cannot have a display and an input panel, and cannot be directly connected to a host computer. In contrast, the print control apparatus 100 as a control unit of the printer may be provided with a display and an input panel, for example, in the operation unit 18, and may have an interface with a host computer in many cases. Therefore, it is possible to use the characteristics of the ink input from the display and the input panel or the characteristics of the ink input from the host computer and set the drive voltage waveform accordingly. Therefore, when the printing control apparatus 100 is provided with the information without providing the inkjet heads 1A to 1D with the detailed information on the ink and the values of the WG register, the WGG register 400, and the like are set based on the information, a flexible printer that can be used under wider conditions can be provided.
Returning to the description of fig. 6, the print data buffer 74 is composed of an input buffer for storing data sent from the print data output unit 205 and an output buffer for outputting the data to the waveform selection unit 75. Each buffer has a capacity capable of storing gradation value data of each channel in an amount corresponding to the number of channels. When a print trigger is given to the print data buffer 74, the print data of the input-side buffer is transmitted to the output-side buffer.
As shown in fig. 11, the waveform selection unit 75 includes a selector 500, a decoder 501, and a peak clipping/dead time generation circuit 502. As shown in the circuit diagram of fig. 12 a, the output buffer 76 includes a first transistor Q0 for applying a voltage V0 to the actuator, a second transistor Q1 for applying a voltage V1 to the actuator, and a third transistor Q2(Q2p and Q2n) for applying a voltage V2 to the actuator.
As shown in fig. 11, print data is given to the selected input of the waveform selection unit 75. The print data given to the waveform selection unit 75 is a 3-bit signal having a value of 0 to 7. The values of 0-7 correspond to gray scale values of 0-7. The selector 500 of the waveform selection unit 75 selects one encoded drive voltage waveform from among the encoded drive voltage waveforms WK0 to WK7 according to the values of 0 to 7 of the print data. The encoded drive voltage waveform is a 2-bit signal stream having a value of 0 to 3. The 2-bit signal has a value of 0 to 3 in a state shown in fig. 12 (b), in which one of a first transistor Q0 for applying a voltage V0 to the actuator, a second transistor Q1 for applying a voltage V1 to the actuator, and a third transistor Q2(Q2p and Q2n) for applying a voltage V2 to the actuator is turned on or off. The state value corresponds to the state value of the WG register. The signals decoded by the decoder 501 are a0in, a1in, and a2 in.
The spike pulse generated at the time of decoding is removed by the peak clipping/dead time generation circuit 502. At the same time, the peak clipping/dead time generation circuit 502 generates signals a0, a1, a2, in which dead time (dead time) for temporarily turning off all transistors at the timing when the transistors Q1, Q2(Q2p, Q2n), and Q0 that are on are switched is inserted into the signals a0, a1, and a 2. The signals a0, a1, a2 are sent to the output buffer 76. When the signal a0 is "H", the first transistor Q0 is turned on, and a voltage V0(═ 0V) is applied to the actuator 8. When the signal a1 is "H", the second transistor Q1 is turned on, and the voltage V1 is applied to the actuator 8. When the signal a2 is "H", the third transistor Q2(Q2p, Q2n) is turned on, and the voltage V2 is applied to the actuator 8. When all of the signals a0, a1, and a2 are "L", all of the first to third transistors Q0, Q1, and Q2(Q2p, Q2n) are turned off, and the terminals of the actuator 8 have high impedance. Two or more of the signals a0, a1, a2 do not become "H" at the same time.
Fig. 13 shows a series of drive voltage waveforms applied to the actuator 8 to perform a series of printing operations. The print cycle was 20 mus. In the initial state, a voltage of 0V is applied to the actuator 8. Before printing, the printing control apparatus 100 issues a wake-up command (gradation value 5) for waking up all the actuators 8 at once and a print trigger. The waveform selection unit 75 selects the coded drive voltage waveform WK5 from the coded drive voltage waveforms WK0 to WK7, and the output buffer 76 controls on/off of the first to third transistors Q0, Q1, and Q2(Q2p and Q2n) to apply a wake-up voltage waveform corresponding to the coded drive voltage waveform WK5 to the actuator 8. Thereby, the voltage applied to the actuator 8 rises from the voltage V0 to the voltage V1. I.e. from a first voltage to a second voltage (first voltage < second voltage). When the voltage rises to V1 for waking up, ink cannot be ejected. Therefore, in order to suppress the pressure amplitude at the time of voltage rise and to cancel the pressure vibration, a step (step) is provided in the wake-up voltage waveform, in which the voltage is set to the voltage V2 for the first 2 μ s. 2 mus is the half period of the pressure oscillation. The half-cycle of the pressure oscillation is also referred to as AL (AcousticLength).
Then, the print control apparatus 100 sequentially issues print data (gradation values 1 to 4) and a print trigger, and applies a drive voltage waveform to the actuator 8 of the nozzle 51 from which ink is to be ejected n times (n ≧ 1). However, as shown in fig. 13, the time from the wake-up to the first printing is secured for two or more cycles of the printing cycle (20 μ s in this example). The time of two cycles or more can be secured by adjusting the time when the next print trigger is issued, or by issuing the print data (gradation value 0) and the print trigger in succession and continuing to apply the voltage V1. The reason why the bias voltage before printing is applied while securing a time of two or more cycles of the drive voltage waveform from the wake-up to the first printing will be described with reference to fig. 14 to 15.
When a bias voltage is applied to the actuator 8, the polarization of the actuator 8 changes. At this time, if the application time of the bias voltage before printing is short, printing is started before the change in polarization is saturated, and therefore, the piezoelectric constant is high only at the time of printing the first dot, and there is a case where printing is deepened at the time of starting printing as shown in an example in fig. 14. That is, a problem of deterioration in print quality is caused.
In order to examine this phenomenon, the actuator 8 was driven with a voltage waveform shown in fig. 15 (a), and the change in the electrostatic capacitance of the actuator 8 was examined. The driving voltage waveform of the ejected ink is an encoded driving voltage waveform WK4 for one dot formed by four ink drops. 2 mus is the half period of the pressure oscillation. The results are shown in fig. 15 (b). As is clear from the result of fig. 15 (b), even when a bias voltage of 20 μ s (i.e., one period of the printing period) is applied before the drive voltage waveform for ejecting ink is applied, the change in the electrostatic capacitance is not saturated. When a bias voltage of 100 μ s (five cycles of the printing cycle) is applied in total before and after the ejection, the electrostatic capacitance decreases, and the electrostatic capacitance at the second dot and thereafter is stabilized. However, when the bias voltage is stopped and then temporarily placed, the electrostatic capacitance is restored. This phenomenon is a cause of the phenomenon that the printing of the first dots becomes deep as shown in fig. 14. Therefore, at least two cycles or more of the drive voltage waveform are ensured from the wake-up to the first printing, and the first dot is suppressed from becoming deep. More preferably, five cycles or more corresponding to 100 μ s are ensured in total before and after ejection or before ejection. Since both the wake-up command and the print data (gradation value 5) are transmitted from the print control apparatus 100 to the head drive circuit 7, the time from wake-up to the first printing can be freely adjusted.
In the example of fig. 13, after the wake-up voltage waveform is applied to the actuator 8 and the voltage V1 is further applied as the bias voltage (two periods totaling the print period equal to or more than 40 μ s), the print control apparatus 100 sequentially issues the print data (gradation values 1, 2, 3, and 4) and the print triggers 2 to 5, and performs printing of four dots in the order of gradation values 1, 2, 3, and 4. Then, the print control apparatus 100 issues print data (tone value 0) and print triggers 6 to 7 in order, applies the voltage V1 to the actuator 8, and temporarily stops printing in this state. During this time, the voltage V1 is maintained. In this example, the voltage V1 is maintained for four cycles (80 μ s) of the printing cycle. Next, the print control apparatus 100 issues the print data (tone values 1, 2, 3, and 4) and the print triggers 9 to 12 in order again, and performs four-dot printing in the order of tone values 1, 2, 3, and 4. Then, the print control apparatus 100 issues the print data (gradation value 0) and the print trigger 13, and applies the voltage V1 to the actuator 8.
When a series of printing operations are completed, the printing control apparatus 100 issues a sleep command (gradation value 6) and a print trigger 14. When the sleep command is executed, the waveform selection unit 75 selects the coded drive voltage waveform WK6 from the coded drive voltage waveforms WK0 to WK7, and the output buffer 76 controls on/off of the first to third transistors Q0, Q1, and Q2(Q2p and Q2n) to apply a sleep voltage waveform corresponding to the coded drive voltage waveform WK6 to the actuator 8. The applied voltage of the actuator 8 is dropped from the voltage V1 to the voltage V0. I.e. from the second voltage to the first voltage (first voltage < second voltage). When the voltage is lowered to the voltage V0 for sleep, ink cannot be ejected. In order to suppress the pressure amplitude at the time of voltage drop and eliminate the pressure vibration, a stage is provided in which the voltage is set to V2 for the first 2 μ s period in the sleep waveform. 2 mus is the half period of the pressure oscillation. Then, the voltage V0 is maintained until the next print trigger is input.
In another example shown in fig. 16, a sleep is provided between the printing of the first four dots and the printing of the next four dots, and the application of the bias voltage is stopped. Unlike the inkjet heads 1A to 1D, the print control device 100 has a plurality of line buffers, and thus has information on whether or not there is ejection thereafter in a plurality of lines. Therefore, the printing control apparatus 100 can determine whether to perform next printing immediately after several lines or to temporarily stop ejecting for several tens or hundreds of lines in the future. If it is determined that the ejection is not performed for several hundred lines or more after that, the print control apparatus 100 issues a sleep command (gradation value 6) and a print trigger 7. By performing the sleep, the voltage applied to the actuator 8 temporarily becomes the voltage V0(═ 0V). It is preferable that the time for maintaining the voltage V0(═ 0V) from the sleep is ensured for two or more cycles of the printing cycle (20 μ s in this example).
Then, the printing control apparatus 100 issues the wakeup command (tone value 5) and the print trigger 8 before two cycles (40 μ s) earlier than the next ejection by the print cycle. The voltage applied to the actuator 8 by the wake-up voltage waveform rises to the voltage V1, and maintains the applied voltage V1 as a bias voltage. By ensuring the application time of the bias voltage for two or more periods of the printing period before ejection, the first dot of the next ejection can be prevented from becoming deep, and good printing quality can be obtained.
Further, although the above example is one in which the uniform wake-up and the uniform sleep are instructed, even if the wake-up data (gradation value 5) and the sleep data (gradation value 6) are included in the print data and the wake-up and the sleep are performed on the individual actuators 8, the first dots can be prevented from being deepened in the same manner, and good print quality can be obtained.
That is, according to the above-described embodiment, the application of the bias voltage applied to the electrostatic capacitive actuator can be stopped, and the characteristics of the actuator at the next liquid discharge can be stabilized.
Next, a modification of the setting values of the awake WG register GW and the sleep WG register GS will be described with reference to fig. 17. As shown in fig. 17, the WG register GW sets a state value 3 for turning off all of the first to third transistors Q0, Q1, and Q2 at two locations where the voltage waveform rises from the voltage V0 to the voltage V2 and where the voltage waveform rises from the voltage V2 to the voltage V1. In the figure, the region is indicated by "Hi-Z". Specifically, after the third transistor Q2 is turned on and charging to the actuator 8 is started, the state 3 is inserted for a predetermined time (for example, 0.1 μ s) and the third transistor Q2 is turned off at a time when a predetermined time (for example, 0.1 μ s) shorter than the time required for completing the charging operation has elapsed since the voltage waveform started to rise to the voltage V2. After the predetermined time has elapsed, the third transistor Q2 is turned on again. Then, the second transistor Q1 is turned on, and at a time when a predetermined time (for example, 0.1 μ s) shorter than the time required to complete the charging operation has elapsed since the start of the rise of the voltage waveform to the voltage V1, the state 3 is inserted for a predetermined time (for example, 0.1 μ s) and the second transistor Q1 is turned off. After the predetermined time has elapsed, the second transistor Q1 is turned on again. By inserting state 3 in this way, the rise time of the voltage is extended. Since the rising charge and the falling discharge of the voltage waveform require several hundred nanoseconds, the rise time is adjusted by changing to the state value 3 in this time. By adjusting the rise time of the wake-up voltage waveform in this manner, unnecessary ink ejection during driving with the wake-up voltage waveform can be made less likely to occur.
Similarly, the WG register GS also sets a state value 3 for turning off all of the first to third transistors Q0, Q1, and Q2 at two locations where the voltage waveform falls from the voltage V1 to the voltage V2 and where the voltage waveform falls from the voltage V2 to the voltage V0. In the figure, the region is indicated by "Hi-Z". Specifically, after the third transistor Q2 is turned on and the discharge of the actuator 8 is started, the state 3 is inserted for a predetermined time (for example, 0.1 μ s) and the third transistor Q2 is turned off at a time when a predetermined time (for example, 0.1 μ s) shorter than the time required for completing the discharge operation has elapsed since the voltage waveform started to fall to the voltage V2. After the predetermined time has elapsed, the third transistor Q2 is turned on again. Then, the first transistor Q0 is turned on, and at a time when a predetermined time (for example, 0.1 μ s) shorter than the time required to complete the discharge operation has elapsed since the voltage waveform started to fall to the voltage V0, the state 3 is inserted for a predetermined time (for example, 0.1 μ s) and the first transistor Q0 is turned off. After the predetermined time has elapsed, the first transistor Q0 is turned on again. By inserting state 3 in this way, the fall time of the voltage is extended. By adjusting the fall time of the sleep voltage waveform in this manner, unnecessary ink ejection during driving with the sleep voltage waveform can be made less likely to occur.
Another modification of the setting values of the awake WG register GW and the sleep WG register GS will be described with reference to fig. 18. In the example shown in fig. 16, the voltage applied to the actuator 8 is lowered to the voltage V0 (> 0V) to completely sleep when the section in which ink is not ejected continues during printing, but in this modification, the voltage applied to the actuator 8 is lowered to the voltage V2 (> 0V) instead to wait. Namely, a low voltage wake-up state (dark wake) is set. Therefore, the state value 2 is set to all the states S0 to S8 of the WG register GW. I.e., fixed to voltage V2. On the other hand, the state value 0 is set to all the states S0 to S8 of the WG register GS. I.e., fixed to voltage V0. Since the voltage is fixed, the set values of the timers t0 to t7 may be arbitrary values.
Fig. 19 shows an example of the allocation of WG registers GW, GS, G0, G1, and G2 to gray scale values 0 to 7 and generated coded drive voltage waveforms WK0 to WK7 when the WG registers GW and GS shown in fig. 18 are used. As shown in fig. 19, the encoded drive voltage waveform WK5 corresponding to the gradation value 5 becomes a low-voltage wake-up state (dark wake) in which the voltage V2 is applied to the actuator 8 over the entire time domain, and the encoded drive voltage waveform WK6 corresponding to the gradation value 6 becomes a sleep state in which the voltage 0(═ 0V) is applied to the actuator 8 over the entire time domain. Therefore, the value of the WG register GW (voltage V2) is output to the encoded drive voltage waveform WK5 corresponding to the gradation value 5, and the final value is held. The value of the WG register GS (voltage V0) is output to the coded drive voltage waveform WK6 corresponding to the gradation value 6, and the final value is held. Instead of using the gradation value 7, the encoded drive voltage waveform WK6 of the gradation value 6 is used to maintain the sleep. The gradation values 0 to 4 are the same as those in the example shown in FIG. 10.
Fig. 20 shows a series of drive voltage waveforms applied to the actuator 8 to perform a series of printing operations. The print cycle was 20 mus. In the initial state, a voltage of 0V is applied to the actuator 8. When a wake-up command (gradation value 5) and a print trigger 1 are issued from the print control apparatus 100 before printing, the waveform selection unit 75 selects the coded drive voltage waveform WK5, and the voltages applied to all the actuators 8 rise from the voltage 0V to the voltage V2. Namely, the low voltage wake-up state (darkwake) is established. Then, for example, when the print data (gradation value 0) and the print trigger 2 are issued from the print control apparatus 100 to the actuator 8 that performs ejection, the waveform selection unit 75 selects the encoded drive voltage waveform WK0, and the voltage applied to the actuator 8 rises from the voltage V2 to the voltage V1. That is, the wake-up voltage waveform is applied and the bias voltage is applied. Then, the print control apparatus 100 issues the print data (tone value 0) and the print trigger 3 again. As a result, the application time of the bias voltage is maintained at two or more cycles of the print cycle before ejection, and the characteristics of the actuator 8 are stabilized.
Then, the print control apparatus 100 issues print data (gradation value 4) and a print trigger 4, and performs printing of one dot at the gradation value 4. When the next ejection is not performed, the print control apparatus 100 issues the print data (tone value 0) and the print trigger 5, but when it is determined that the ejection is not performed temporarily thereafter, the print control apparatus 100 issues, for example, the wakeup command (tone value 5) and the print trigger 7. The gradation value 5 may be given as print data. The waveform selection unit 75 selects the coded drive voltage waveform WK5, and the voltage applied to the actuator 8 drops from the voltage V1 to the voltage V2, and changes to a low-voltage wake-up state (dark wake, shown as "low-voltage wake-up" in the figure). The print control apparatus 100 issues the print data (gradation value 0) and the print trigger 10 two print cycles earlier than when the ejection is restarted. The waveform selection unit 75 selects the coded drive voltage waveform WK0, and the voltage applied to the actuator 8 rises from the voltage V2 to the voltage V1. That is, the state is changed to the state in which the bias voltage is applied. Then, the print control apparatus 100 issues the print data (tone value 0) and the print trigger 11 again. This maintains the application time of the bias voltage to two or more print cycles before ejection, thereby stabilizing the characteristics of the actuator 8.
Then, the print control apparatus 100 issues print data (gradation value 1) and a print trigger 12, and performs printing of one dot at the gradation value 1. In the next print cycle, print data (gradation value 4) and a print trigger 13 are issued from the print control apparatus 100, and printing is performed for one dot at the gradation value 4. Then, the print control apparatus 100 issues the print data (gradation value 0) and the print trigger 14, and applies the voltage V1 to the actuator 8. If it is determined at this point that ejection is not to be performed for a while thereafter, the print control apparatus 100 issues a wake-up command (gradation value 5) and a print trigger 15, and lowers the voltage applied to the actuator 8 to the voltage V2. Further, in the next print cycle, a sleep command (gradation value 6) and a print trigger 16 are issued, and the voltages applied to all the actuators 8 are reduced to a voltage V0(═ 0V). Namely, the sleep mode is set to the full sleep mode.
In the above embodiment, the inkjet heads 1A and 101A of the inkjet printer 1 have been described as an example of the liquid ejecting apparatus, but the liquid ejecting apparatus may be a modeling material ejecting head of a 3D printer or a sample ejecting head of a dispensing apparatus. Of course, the actuator 8 is not limited to the configuration and arrangement of the above embodiment in the same manner as the capacitive load.
That is, the actuator driving circuit of the liquid ejecting apparatus according to (1) the embodiment includes: a discharge waveform generating section for receiving gradation data composed of a plurality of bits and applying a drive voltage waveform for discharging a liquid to the actuator according to a gradation value of the gradation data; a sleep waveform generating unit that converts the voltage of the actuator to a first voltage without ejecting liquid; and a wake-up waveform generating unit that converts the voltage of the actuator to a second voltage that is greater than the first voltage without ejecting liquid.
(2) The first voltage is a low voltage that is low to the extent that the actuator does not change over time.
(3) The second voltage is the same as an initial voltage and/or an end voltage of a drive voltage waveform for ejecting the liquid.
(4) When a first command for activating the sleep waveform generating section is assigned to a part of a plurality of bits constituting the gradation data and the first command is extracted, a sleep waveform is given to the actuator.
(5) When a second command for activating the wake-up waveform generating unit is allocated to a part of a plurality of bits constituting the gradation data and the second command is extracted, a wake-up waveform is given to the actuator.
(6) When a third instruction to hold the voltage applied to the actuator at the first voltage is allocated to a part of a plurality of bits constituting the gradation data and the third instruction is extracted, the voltage applied to the actuator is held at the first voltage.
