JP2007125823A - Liquid ejector and method for driving liquid ejecting section - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejector in which possibility of damaging a circuit is reduced even when switches for switching input of a drive waveform are turned on simultaneously. <P>SOLUTION: The liquid ejector comprises a first and second drive signal generating sections, a liquid ejecting section driven with the drive signal to eject a liquid drop, and a control section for controlling the first and second drive signal generating sections to generate drive signals, selecting any one of the drive signals generated from the first and second drive signal generating sections and driving the liquid ejecting section with a selected drive signal. When a dot is formed, the control section controls the first and second drive signal generating sections to generate drive signals for forming dots. When a dot is not formed, the control section controls the first and second drive signal generating sections to generate the same drive signals for not forming a dot. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus and a method for driving a liquid ejection unit.

A liquid ejecting apparatus that ejects ink droplets to form dots is known that uses two drive signals (for example, Patent Document 1).
A liquid ejection device that ejects ink droplets drives an actuator for ejecting ink droplets even when dots are not formed, such as stirring ink droplets on a nozzle surface. Thus, when the actuator is driven but no dot is formed, one of the two drive signals has a pulse for driving the actuator, and the other drive signal holds a constant potential of approximately 0 (V). Then, the drive signal having the pulse is applied to the actuator.
JP 2000-52570 A

  When a dot is not formed for driving an actuator, a plurality of switches for switching input of drive signals to the actuator may be turned on due to the influence of noise or the like. In such a case, a current resulting from a potential difference between different drive signals may flow into an unexpected circuit and damage the circuit.

  The present invention has been made in view of such circumstances, and even when dots are not formed, even when a plurality of switches for switching the input of the drive signal are turned on at the same time, the potential difference between the different drive signals. An object of the present invention is to provide a liquid ejecting apparatus in which the possibility of circuit damage resulting from the above is reduced.

The main invention for achieving the above object is:
(1) a first drive signal generation unit and a second drive signal generation unit that generate a drive signal;
(2) a liquid ejection unit that is driven according to the drive signal and capable of ejecting liquid droplets;
(3) Either of the drive signals generated by the first drive signal generator and the second drive signal generator while causing the first drive signal generator and the second drive signal generator to generate a drive signal. A control unit that drives the liquid ejection unit according to the selected drive signal,
At the time of dot formation in which the liquid droplet is landed on a medium to form a dot, a drive signal for dot formation is generated in the first drive signal generation unit and the second drive signal generation unit,
When the liquid ejection unit is driven by the drive signal but the dots are not formed, the same dot non-formation drive signal is sent to the first drive signal generation unit and the second drive signal generation unit. A control unit to generate,
It is a liquid discharge apparatus provided with.

Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

=== Summary of disclosure ===
At least the following matters will become clear from the description of the present specification and the accompanying drawings.

(1) a first drive signal generation unit and a second drive signal generation unit that generate a drive signal;
(2) a liquid ejection unit that is driven according to the drive signal and capable of ejecting liquid droplets;
(3) Either of the drive signals generated by the first drive signal generator and the second drive signal generator while causing the first drive signal generator and the second drive signal generator to generate a drive signal. A control unit that drives the liquid ejection unit according to the selected drive signal,
At the time of dot formation in which the liquid droplet is landed on a medium to form a dot, a drive signal for dot formation is generated in the first drive signal generation unit and the second drive signal generation unit,
When the liquid ejection unit is driven by the drive signal but the dots are not formed, the same dot non-formation drive signal is sent to the first drive signal generation unit and the second drive signal generation unit. A control unit to generate,
A liquid ejection apparatus comprising:
According to this liquid ejection apparatus, even when a plurality of switches for switching the input of the drive signal are turned on at the same time, the potential difference of the drive signal is 0. Can be reduced.

  In this liquid ejection apparatus, it is preferable that the control unit selects a signal from the first drive signal generation unit when the dots are not formed. In addition, when the dots are not formed, it is preferable that the control unit alternately selects the drive signal from the first drive signal generation unit and the drive signal from the second drive signal generation unit at a predetermined cycle. . Further, the control unit includes a first switch provided between the first drive signal generation unit and the liquid ejection unit in order to select a drive signal from the first drive signal generation unit, and the second In order to select a drive signal from the drive signal generation unit, it is preferable to include a second switch provided between the second drive signal generation unit and the liquid ejection unit. Further, it is desirable that the time when the dots are not formed is when the liquid droplets are agitated in the liquid ejecting portion. In addition, it is preferable that the apparatus further includes a moving mechanism for moving the liquid discharge portion, and when the dots are not formed, the movement mechanism is moving the liquid discharge portion without discharging a liquid drop. In addition, it is desirable that the time when the dots are not formed is during a flushing operation in which the liquid droplets are ejected but not landed on the medium.

(1) a first drive signal generation unit and a second drive signal generation unit that generate a drive signal;
(2) a liquid ejection unit that is driven in accordance with a pulse included in the drive signal and is capable of ejecting a liquid droplet;
(3) Either of the drive signals generated by the first drive signal generator and the second drive signal generator while causing the first drive signal generator and the second drive signal generator to generate a drive signal. A control unit that drives the liquid ejection unit according to the selected drive signal,
At the time of dot formation in which the liquid droplet is landed on a medium to form a dot, a drive signal for dot formation is generated in the first drive signal generation unit and the second drive signal generation unit,
When the liquid ejection unit is driven by the drive signal but the dot is not formed, the dot non-formation drive signal is generated by the first drive signal generation unit and the constant potential signal is generated by the second drive. A control unit for generating the signal generation unit;
The potential difference between the pulse start potential and the constant potential signal included in the dot non-formation drive signal is smaller than the maximum potential difference between the start potential and the dot non-formation drive signal potential. A liquid ejection device is provided.

  The constant potential signal generated by the second drive signal generator is preferably a constant potential signal having the same potential as the start potential of the pulse.

  According to this liquid ejection apparatus, even when a plurality of switches for switching the input of the drive signal are turned on at the same time, the potential difference of the drive signal is reduced, so that the circuit can be damaged due to the current resulting from the potential difference. Can be reduced.

And (1) generating a first drive signal and a second drive signal, which are the same drive signals for non-dot formation at the time of non-formation of dots,
(2) generating a first drive signal and a second drive signal for dot formation at the time of dot formation;
(3) selecting either the first drive signal or the second drive signal;
(4) applying the selected drive signal to the liquid ejection unit;
A liquid discharge method including

  According to this method for driving the liquid ejection unit, since the first drive signal and the second drive signal are the same drive signal when dots are not formed, a plurality of switches for switching the two and applying the drive signal to the actuator Even when they are turned on at the same time, the possibility of damage to the circuit due to the current resulting from the potential difference flowing into the circuit with the lower potential can be reduced.

And (1) generating a first drive signal for non-dot formation and a second drive signal that is a constant potential signal at the time of dot non-formation;
(2) generating a first drive signal and a second drive signal for dot formation at the time of dot formation;
(3) selecting either the first drive signal or the second drive signal;
(4) applying the selected drive signal to the liquid ejection unit;
And the potential difference between the start potential of the pulse included in the first drive signal for non-dot formation and the constant potential signal is the maximum between the start potential and the potential of the first drive signal for non-dot formation Provided is a liquid ejection unit driving method that is smaller than a potential difference.

  According to the driving method of the liquid ejection unit, a constant potential signal having the same potential as the intermediate potential of the first drive signal is generated as the second drive signal. In this way, the potential difference between the first drive signal and the second drive signal is reduced. Therefore, even when a plurality of switches for switching between the two and applying a drive signal to the actuator are turned on at the same time, the current due to the potential difference generates the drive signal generator or the second drive signal that generates the first drive signal. It is possible to reduce the risk of damaging the drive signal generation unit.

=== Printing system ===
First, the printer 1 as a liquid ejection apparatus in this embodiment will be described together with a printing system. The printing system includes a printer 1 and a computer 110 that is a print control apparatus that controls the operation of the printer 1.

  FIG. 1 is a diagram illustrating the configuration of the printing system 100. The printing system 100 includes a printer 1, a computer 110, a display device 120, an input device 130, and a recording / reproducing device 140.

  The printer 1 prints an image on a medium such as paper, cloth, or film. In addition, regarding this medium, in the following description, a sheet S (see FIG. 3A), which is a typical medium, will be described as an example. The computer 110 is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer 110 outputs print data corresponding to the image to the printer 1. Computer programs such as application programs and printer drivers are installed in the computer 110. The display device 120 has a display. The display device 120 is for displaying a user interface of a computer program, for example. The input device 130 is a keyboard 131 or a mouse 132, for example. The recording / reproducing device 140 is, for example, a flexible disk drive device 141 or a CD-ROM drive device 142.

=== Computer configuration ===
<Configuration of Computer 110>
FIG. 2 is a block diagram illustrating configurations of the computer 110 and the printer 1.
First, the configuration of the computer 110 will be briefly described. The computer 110 includes the recording / reproducing device 140 and the host-side controller 111 described above. The recording / reproducing apparatus 140 is communicably connected to the host-side controller 111, and is attached to the housing of the computer 110, for example. The host-side controller 111 performs various controls in the computer 110, and the display device 120 and the input device 130 described above are also connected to be communicable. The host-side controller 111 includes an interface unit 112, a CPU 113, and a memory 114. The interface unit 112 is interposed between the printer 1 and exchanges data. The CPU 113 is an arithmetic processing unit for performing overall control of the computer 110. The memory 114 is used to secure an area for storing a computer program used by the CPU 113, a work area, and the like, and includes a RAM, an EEPROM, a ROM, a magnetic disk device, and the like. As described above, computer programs stored in the memory 114 include application programs and printer drivers. The CPU 113 performs various controls according to the computer program stored in the memory 114.

  The print data is data in a format that can be interpreted by the printer 1 and includes various command data and pixel data. The command data is data for instructing the printer 1 to execute a specific operation. The command data includes, for example, command data for instructing paper feed, command data for indicating the carry amount, and command data for instructing paper discharge. The pixel data is data related to pixels of an image to be printed. Here, the pixel is a square grid virtually defined on the paper, and indicates a region where dots are formed. The pixel data in the print data is converted into data relating to dots formed on the paper (for example, dot size data).

=== Printer ===
<About the configuration of the printer 1>
Next, the configuration of the printer 1 as a liquid ejection device will be described. Here, FIG. 3A is a diagram illustrating a configuration of the printer 1 of the present embodiment. FIG. 3B is a side view illustrating the configuration of the printer 1 of the present embodiment. In the following description, FIG. 2 is also referred to.

  As shown in FIG. 2, the printer 1 includes a paper transport mechanism 20, a carriage moving mechanism 30, a head unit 40, a detector group 50, a printer-side controller 60, and a drive signal generation circuit 70. In the present embodiment, the printer-side controller 60 and the drive signal generation circuit 70 are provided on a common controller board CTR.

  In the printer 1, the control target unit, that is, the paper transport mechanism 20, the carriage moving mechanism 30, the head unit 40, and the drive signal generation circuit 70 are controlled by the printer-side controller 60. As a result, the printer-side controller 60 prints an image on the paper S based on the print data received from the computer 110. Each detector in the detector group 50 monitors the status in the printer 1. Each detector outputs the detection result to the printer-side controller 60. Upon receiving the detection results from each detector, the printer-side controller 60 controls the control target unit based on the detection results.

<Regarding the paper transport mechanism 20>
The paper transport mechanism 20 feeds the paper S to a printable position, or transports the paper S by a predetermined transport amount in the transport direction. This transport direction is a direction that intersects the carriage movement direction described below. 3A and 3B, the paper transport mechanism 20 includes a paper feed roller 21, a transport motor 22, a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for automatically feeding the paper S inserted into the paper insertion opening into the printer 1 and has a D-shaped cross section in this example. The transport motor 22 is a motor for transporting the paper S in the transport direction. The transport roller 23 is a roller for transporting the paper S sent by the paper feed roller 21 to a printable area. The operation of the transport roller 23 is also controlled by the transport motor 22. The platen 24 is a member that supports the paper S being printed from the back side of the paper S. The paper discharge roller 25 is a roller for carrying the paper S that has been printed.

<About the carriage moving mechanism 30>
The carriage moving mechanism 30 is for moving the carriage CR to which the head unit 40 is attached in the carriage moving direction. The carriage movement direction includes a movement direction from one end side to the other end side and a movement direction from the other end side to the one end side. The carriage moving mechanism 30 includes a carriage motor 31, a guide shaft 32, a timing belt 33, a driving pulley 34, and a driven pulley 35. The carriage motor 31 corresponds to a drive source for moving the carriage CR. A drive pulley 34 is attached to the rotation shaft of the carriage motor 31. The drive pulley 34 is disposed on one end side in the carriage movement direction. A driven pulley 35 is disposed on the other end side in the carriage movement direction on the opposite side to the drive pulley 34. The timing belt 33 is connected to the carriage CR and is spanned between a driving pulley 34 and a driven pulley 35. The guide shaft 32 supports the carriage CR in a movable state. The guide shaft 32 is attached along the carriage movement direction. Accordingly, when the carriage motor 31 operates, the carriage CR moves along the guide shaft 32 in the carriage movement direction.

<About the head unit>
The head unit 40 is for ejecting ink toward the paper S. The head unit 40 includes a head 41 and a head controller HC. Here, FIG. 4A is a cross-sectional view for explaining the structure of the head 41. FIG. 4B is a diagram for explaining the arrangement of the nozzle rows. For convenience, the head 41 will be described here, and the head controller HC will be described later.

  The illustrated head 41 includes a flow path unit 41A and an actuator unit 41B. The flow path unit 41A includes a nozzle plate 411 provided with a nozzle Nz, a storage chamber forming substrate 412 in which an opening serving as an ink storage chamber 412a is formed, and a supply port forming substrate 413 in which an ink supply port 413a is formed. have. The nozzle plate 411 is bonded to one surface of the storage chamber forming substrate 412, and the supply port forming substrate 413 is bonded to the other surface. The actuator unit 41B has a pressure chamber forming substrate 414 in which an opening to be a pressure chamber 414a is formed, a vibration plate 415 that partitions a part of the pressure chamber 414a, and an opening to be a supply side communication port 416a. A lid member 416 and a piezo element 417 formed on the surface of the vibration plate 415 are provided. The head 41 is formed with a series of flow paths from the ink storage chamber 412a through the pressure chamber 414a to the nozzle Nz. In use, this flow path is filled with ink, and by deforming the piezo element 417, ink can be ejected from the corresponding nozzle Nz.

<Regarding the detector group 50>
The detector group 50 is for monitoring the status of the printer 1. As shown in FIGS. 3A and 3B, the detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detector 53, and a paper width detector. The linear encoder 51 is for detecting the position of the carriage CR in the carriage movement direction and outputting pulses ENC-A and ENC-B, which will be described later. The rotary encoder 52 is for detecting the rotation amount of the transport roller 23. The paper detector 53 is for detecting the leading end position of the paper S to be printed. The paper width detector 54 is for detecting the width of the paper S to be printed.

<About the linear encoder 51>
FIG. 12 schematically shows the configuration of the linear encoder 51. The linear encoder 51 includes a linear encoder code plate 464 and a detection unit 466. As shown in FIG. 3, the linear encoder code plate 464 is attached to the frame side inside the inkjet printer 1. On the other hand, the detection unit 466 is attached to the carriage CR side. When the carriage CR moves along the guide rail 32, the detection unit 466 moves relatively along the linear encoder code plate 464. Accordingly, the detection unit 466 detects the movement amount of the carriage CR.

  FIG. 13 schematically shows the configuration of the detection unit 466. The detection unit 466 includes a light emitting diode 452, a collimator lens 454, and a detection processing unit 456. The detection processing unit 456 includes a plurality of (for example, four) photodiodes 458, a signal processing circuit 460, and, for example, two comparators 462A and 462B.

  When the voltage Vcc is applied to both ends of the light emitting diode 452 via a resistor, light is emitted from the light emitting diode 452. This light is condensed into parallel light by the collimator lens 454 and passes through the linear encoder code plate 464. The linear encoder code plate 464 is provided with slits at predetermined intervals (for example, 1/180 inch (1 inch = 2.54 cm)).

  The parallel light that has passed through the linear encoder code plate 464 enters each photodiode 458 through a fixed slit (not shown), and is converted into an electrical signal. The electric signals output from the four photodiodes 458 are subjected to signal processing in the signal processing circuit 460, the signals output from the signal processing circuit 460 are compared in the comparators 462A and 462B, and the comparison result is output as a pulse. Pulses ENC-A and ENC-B output from the comparators 462A and 462B are output from the linear encoder 51.

<About PTS>
Both the latch signal (LAT signal) and the change signal (CH signal) input to the head controller HC are generated based on PTS (Pulse Timing Signal). PTS is a signal that defines the timing at which pulses are generated in the latch signal (LAT signal) and the change signal (CH signal). PTS pulses are generated based on output pulses ENC-A and ENC-B from the linear encoder 51 (detection unit 466). That is, the PTS pulse is generated according to the amount of movement of the carriage CR.

  FIG. 14 illustrates in detail the timing relationship among the PTS, the latch signal (LAT signal), and the change signal (CH signal). The PTS generates a pulse at a predetermined period T0 when the carriage CR is moving at a constant speed. Each of the latch signal (LAT signal) and the change signal (CH signal) is generated based on the pulse generated in the PTS. The pulse of the latch signal (LAT signal) is generated immediately after the pulse is generated by PTS. On the other hand, the change signal (CH signal) is generated after a predetermined time elapses after the pulse is generated by the PTS. Each pulse of the latch signal (LAT signal) and the change signal (CH signal) is generated whenever a pulse is generated in the PTS.

  The PTS is generated by the printer-side controller 60. The printer-side controller 60 generates PTS pulses based on the output pulses ENC-A and ENC-B from the linear encoder 51 (detection unit 466), and the pulses are generated based on the print data sent from the computer 110. The generation timing and cycle are appropriately changed.

<About timer PTS>
When dots are formed, that is, when the carriage CR is moving, a latch signal and a change signal input to the head controller HC are generated based on the PTS. However, the PTS cannot be output because the carriage CR is stationary during a preliminary operation after power-on, which will be described later, and during normal flushing.

  Even when the carriage CR is stationary, a drive signal is generated for the flushing operation to eject ink droplets, or the ink in the vicinity of the nozzles is vibrated and agitated to prevent ink thickening. There is a need. In such a case, the latch signal and the change signal are generated using a timer PTS generated based on the clock signal instead of the PTS.

  The timer PTS is generated by converting the clock signal of the CPU 62 in the printer-side controller 60 into a predetermined frequency. As a conversion method, for example, the clock signal of the CPU 62 is acquired, the pulses of the clock signal are counted, and the pulse of the timer PTS can be generated when a predetermined count value is reached. In this way, even when the carriage CR is stationary, it is possible to generate a timer PTS having a frequency that is a fraction of the clock signal.

  Which of the PTS and the timer PTS is used to generate a latch signal or the like in the printer-side controller 60 depends on switching of a switch (not shown) in the printer-side controller 60. In the present embodiment, the switch is connected so that the timer PTS is used during normal flushing. On the other hand, a switch is connected so that PTS is used during a dot forming operation and a CR operation described later.

<About the printer-side controller 60>
The printer-side controller 60 controls the printer 1. For example, the printer-side controller 60 controls the conveyance amount of the paper conveyance mechanism 20 by controlling the rotation amount of the conveyance motor 22. The printer-side controller 60 controls the position of the carriage CR by controlling the amount of rotation of the carriage motor 31.

  Further, the printer-side controller 60 controls the drive signal generation circuit 70 to generate the drive pulse PS. Here, the drive pulse is a signal for defining from the start to the end of the driving when the piezo element 417 is driven to eject ink. The shape of the drive pulse is determined according to the amount of ink to be ejected. For this reason, when a drive pulse is applied to the piezo element 417, an amount of ink corresponding to the shape of the drive pulse is ejected.

  Also, the printer-side controller 60 sends a head control signal to the head controller HC (clock signal CLK, pixel data SI, latch signal LAT, first change signal CH_A, second change signal CH_B, see FIG. 8). Is output. The head controller HC applies a drive pulse included in the drive signal output from the drive signal generation circuit 70 to the piezo element 417 in accordance with the head control signal.

  As shown in FIG. 2, the printer-side controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a control unit 64. The interface unit 61 exchanges data with the computer 110 which is an external device. The CPU 62 is an arithmetic processing unit for performing overall control of the printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and is configured by a storage element such as a RAM, an EEPROM, or a ROM. In the present embodiment, a part of the memory 63 is used as a program storage area (not shown) and a waveform storage area. The program storage area is an area in which computer programs are stored. The waveform storage area is an area in which waveform data for generating a drive signal is stored.

  The CPU 62 controls each control target unit in accordance with the computer program stored in the program storage area of the memory 63. For example, the CPU 62 controls the paper transport mechanism 20 and the carriage moving mechanism 30 via the control unit 64. Further, the CPU 62 outputs a head control signal for controlling the operation of the head 41 to the head controller HC, and outputs a control signal for generating the drive signal COM to the drive signal generation circuit 70.

  As will be described later, the printer-side controller 60 functions as a control unit that causes the first drive signal generation unit and the second drive signal generation unit to generate the same dot non-formation drive signals. Further, as will be described later, the printer-side controller 60 causes the first drive signal generation unit to generate a dot non-formation drive signal and causes the second drive signal generation unit to generate a constant potential signal. Then, a drive signal in which the potential difference between the pulse start potential and the constant potential signal included in the dot non-formation drive signal is smaller than the maximum potential difference between the start potential and the dot non-formation drive signal is generated. Functions as a control unit.

=== Printing Operation of Printer 1 ===
In the printer 1 having the above-described configuration, the printer-side controller 60 controls the control target units (the paper transport mechanism 20, the carriage moving mechanism 30, the head unit 40, and the drive signal generation circuit 70) according to the computer program stored in the memory 63. Control. Then, by controlling the control target portion, the printing operation on the paper S is performed as follows.

  FIG. 15 is a flowchart for explaining the printing operation. The illustrated printing operation includes a print command receiving operation (S10), a paper feeding operation (S20), a dot forming operation (S30), a conveying operation (S40), a paper discharge determination (S50), a paper discharge process (S60), and It has a print end determination (S70). Hereinafter, each operation will be briefly described.

The print command receiving operation (S10) is an operation of receiving a print command from the computer 110. In this operation, the printer-side controller 60 receives a print command via the interface unit 61.
The paper feeding operation (S20) is an operation for moving the paper S to be printed and positioning it at a printing start position (so-called cueing position). In this operation, the printer-side controller 60 rotates the paper feed roller 21 and the transport roller 23 by driving the transport motor 22 and the like.

  The dot forming operation (S30) is an operation for forming dots on the paper S. In this operation, the printer-side controller 60 drives the carriage motor 31 and outputs a control signal to the drive signal generation circuit and the head 41. Thus, ink is ejected from the nozzles Nz while the head 41 is moving, and dots are formed on the paper S.

The transport operation (S40) is an operation for moving the paper S in the transport direction. In this operation, the printer-side controller 60 drives the carry motor 22 to rotate the carry roller 23. By this transport operation, dots can be formed at positions different from the dots formed by the previous dot formation operation.
The paper discharge determination (S50) is an operation for determining whether or not it is necessary to discharge the paper S to be printed. This determination is made by the printer-side controller 60 based on the presence or absence of print data, for example.
The paper discharge process (S60) is a process of discharging the paper S, and is performed on the condition that “discharge” is determined in the previous paper discharge determination. In this case, the printer-side controller 60 rotates the paper discharge roller 25 to discharge the printed paper S to the outside.
The print end determination (S70) is a determination as to whether or not to continue printing. This determination is also made by the printer-side controller 60.

=== Drive Signal Generation Circuit of the Present Embodiment ===
<About the drive signal generation circuit 70>
The drive signal generation circuit 70 generates a drive signal COM including a drive pulse. This drive signal COM is used in common for all the piezo elements 417 corresponding to one nozzle row.

  FIG. 5A is a block diagram illustrating the configuration of the drive signal generation circuit 70. The drive signal generation circuit 70 of the present embodiment includes a first drive signal generation unit 70A and a second drive signal generation unit. Since the first drive signal generation unit 70A and the second drive signal generation unit 70B have the same configuration, only the first drive signal generation unit 70A will be described here. The first drive signal generation unit 70A includes a first waveform generation circuit 71A and a first current amplification circuit 72A.

  FIG. 5B is a block diagram for explaining the configuration of the first waveform generation circuit 71A. In this figure, the configuration of the second waveform generation circuit 71B is indicated by parenthesized symbols.

  The first waveform generation circuit 71A includes a D / A converter 711A and a voltage amplification circuit 712A. The D / A converter 711A is an electric circuit that outputs a voltage signal corresponding to the DAC value. This DAC value is information for instructing a voltage (hereinafter also referred to as an output voltage) to be output from the voltage amplification circuit 712A, and is output from the CPU 62 based on the waveform data stored in the waveform storage area.

  The voltage amplification circuit 712A amplifies the output voltage from the D / A converter 711A to a voltage suitable for the operation of the piezo element 417. In the voltage amplification circuit 712A of the present embodiment, the output voltage from the D / A converter 711A is amplified to a maximum of 40 several volts. Then, the amplified output voltage is output to the first current amplification circuit 72A as the control signal S_Q1 and the control signal S_Q2.

<Operation of drive signal generator>
Next, a specific example of the operation of the first drive signal generator 70A will be described. FIG. 6 is a diagram for explaining the operation of dropping the output voltage of the first current amplification circuit 72A from the voltage V1 to the voltage V4.

When generating the drive signal COM, the CPU 62 sequentially outputs the DAC value for each update cycle τ to the D / A converter 711A. In the example of FIG. 6, the DAC value corresponding to the voltage V1 is output at the timing t (n) defined by the clock CLK. As a result, the voltage V1 is output from the voltage amplification circuit 712A at the period τ (n). Until the update period τ (n + 4), the DAC value corresponding to the voltage V1 is sequentially input from the CPU 62 to the D / A converter 711A, and the voltage V1 is continuously output from the voltage amplification circuit 712A. At timing t (n + 5), the DAC value corresponding to the voltage V2 is input from the CPU 62 to the D / A converter 711A. As a result, the output of the voltage amplification circuit 712A drops from the voltage V1 to the voltage V2 in the cycle τ (n + 5). Similarly, at timing t (n + 6), the DAC value corresponding to the voltage V3 is input from the CPU 62 to the D / A converter 711A, and the output of the voltage amplification circuit 712A drops from the voltage V2 to the voltage V3. Similarly, since the DAC value is sequentially input to the D / A converter 711A, the voltage output from the voltage amplification circuit 712A gradually decreases. Then, in the period τ (n + 10), the output of the voltage amplification circuit 712A drops to the voltage V4.
The drive signal is output from the first waveform generation circuit 71A by such a method.

<Configuration of current amplifier circuit>
Next, the first current amplifier circuit 72A will be described. FIG. 7A is a diagram illustrating the configuration of the current amplifier circuit 72A (72B). FIG. 7B is an explanatory diagram of a configuration of two transistor pairs and a heat sink.

  The first current amplifying circuit 72A is a circuit for supplying a sufficient current so that a large number of piezo elements 417 can operate without trouble. The first current amplifier circuit 72A includes a first transistor pair 721A that generates heat as the voltage of the drive signal COM changes. The first transistor pair 721A includes an NPN transistor Q1 and a PNP transistor Q2 whose emitter terminals are connected to each other. The NPN transistor Q1 is a transistor that operates when the voltage of the drive signal COM rises. The NPN transistor Q1 has a collector connected to the power supply and an emitter connected to the output signal line of the drive signal COM. The PNP transistor Q2 is a transistor that operates when the voltage drops. The PNP transistor Q2 has a collector connected to the ground (earth) and an emitter connected to the output signal line of the drive signal COM. Note that the voltage at the portion where the emitters of the NPN transistor Q1 and the PNP transistor Q2 are connected to each other (the voltage of the drive signal COM) is fed back to the voltage amplification circuit 712A, as indicated by the symbol FB.

  The operation of the first current amplification circuit 72A is controlled by the output voltage from the first waveform generation circuit 71A. For example, when the output voltage is in the rising state, the NPN transistor Q1 is turned on by the control signal S_Q1. Along with this, the voltage of the drive signal COM also rises. On the other hand, when the output voltage is in a drop state, the PNP transistor Q2 is turned on by the control signal S_Q2. Along with this, the voltage of the drive signal COM also drops. Note that when the output voltage is constant, both the NPN transistor Q1 and the PNP transistor Q2 are turned off. As a result, the first drive signal COM becomes a constant voltage.

  A common heat sink 722 is attached to the first transistor pair 721A and the second transistor pair 721B. The heat sink 722 releases the heat generated by the four transistors to the outside.

<About the drive signal COM>
In the present embodiment, the first drive signal generator 70A and the second drive signal generator 70B generate the respective drive signals COM. Here, description will be made assuming that the first drive signal generation unit 70A generates the first drive signal COM_A, and the second drive signal generation unit 70B generates the second drive signal COM_B. There are several types of drive signals, such as those during preliminary operation, dot formation, CR operation, and normal flushing. Here, drive signals during dot formation will be described as an example.

  FIG. 9 is a diagram illustrating examples of the first drive signal COM_A, the second drive signal COM_B, and necessary control signals.

  The illustrated first drive signal COM_A includes a first waveform section SS11 generated in the period T1, a second waveform section SS12 generated in the period T2, a third waveform section SS13 generated in the period T3, and a period T4. The fourth waveform section SS14 generated in the period T5, the fifth waveform section SS15 generated in the period T5, and the sixth waveform section SS16 generated in the period T6. Among these waveform portions, the first waveform portion SS11, the third waveform portion SS13, and the fifth waveform portion SS15 have a drive pulse PS. The second waveform portion SS12, the fourth waveform portion SS14, and the sixth waveform portion SS16 are constant at the intermediate potential Vc. This intermediate potential Vc corresponds to the start potential and end potential of the drive pulse PS. Accordingly, in the first drive signal COM_A, the drive pulse PS is generated in the period T1, and a constant signal (constant potential signal) is generated at the intermediate potential Vc in the period T2. Further, the driving pulse PS is generated in the periods T3 and T5, and the constant potential signal is generated in the periods T4 and T6. In short, the first drive signal COM_A is a signal that alternately generates the drive pulse PS and the constant potential signal.

  The illustrated second drive signal COM_B includes a first waveform section SS21 generated in the period T1, a second waveform section SS22 generated in the period T2, a third waveform section SS23 generated in the period T3, and a period T4. The fourth waveform section SS24 generated in the period T5, the fifth waveform section SS25 generated in the period T5, and the sixth waveform section SS26 generated in the period T6. In the present embodiment, the first waveform portion SS21 to the sixth waveform portion SS26 of the second drive signal COM_B are determined to have the same time width as the first waveform portion SS11 to the sixth waveform portion SS16 of the corresponding first drive signal COM_A. ing.

  In the second drive signal COM_B, the first waveform portion SS21, the third waveform portion SS23, and the fifth waveform portion SS25 are constant potential signals at the intermediate potential Vc. The second waveform section SS24, the fourth waveform section SS24, and the sixth waveform section SS26 have a drive pulse PS. The second drive signal COM_B can be said to be a signal that alternately generates a constant potential signal and a drive pulse PS.

<About the head controller HC>
Next, the head controller HC will be described. The head controller HC has a function as a controller that selects one of the drive signals COM generated by the first drive signal COM_A and the second drive signal COM_B. Here, FIG. 8 is a block diagram illustrating the configuration of the head controller HC. As shown in FIG. 8, the head controller HC includes a first shift register 81A, a second shift register 81B, a first latch circuit 82A, a second latch circuit 82B, a decoder 83, a control logic 84, A first level shifter 86A, a second level shifter 86B, a first switch 87A, and a second switch 87B are provided. Except for the control logic 84, that is, the first shift register 81A, the second shift register 81B, the first latch circuit 82A, the second latch circuit 82B, the decoder 83, the first level shifter 86A, and the second The level shifter 86B, the first switch 87A, and the second switch 87B are provided for each piezo element 417. Since the piezo element 417 is provided for each nozzle Nz from which ink is ejected, these parts are also provided for each nozzle Nz.

  The head controller HC performs control for ejecting ink based on print data (pixel data SI) from the printer-side controller 60. In this embodiment, pixel data is composed of 2 bits, and this pixel data is sent to the recording head 41 in synchronization with the clock signal CLK. This pixel data is sent in order from the upper bit group to the lower bit group. For example, the upper bit of the nozzle Nz (# 1), the upper bit of the nozzle Nz (# 2), ..., the upper bit of the nozzle Nz (# 179), the upper bit of the nozzle Nz (# 180), the nozzle Nz (# 1) , Lower bits of nozzle Nz (# 2),..., Lower bits of nozzle Nz (# 179), and lower bits of nozzle Nz (# 180). For this reason, first, the upper bit group of the pixel data is set in the second shift register 81B. When the upper bit group of the pixel data is set in the second shift register 81B for all the nozzles Nz, the lower bit group of the pixel data is subsequently set in the second shift register 81B. As the lower bit group of the pixel data is set, the upper bit group of the pixel data is shifted and set in the first shift register 81A.

  A first latch circuit 82A is electrically connected to the first shift register 81A, and a second latch circuit 82B is electrically connected to the second shift register 81B. When the latch signal LAT from the printer-side controller 60 becomes H level, that is, when the latch pulse is input to the first latch circuit 82A and the second latch circuit 82B, the first latch circuit 82A is the upper bit of the pixel data. The second latch circuit 82B latches the lower bits of the pixel data. Pixel data (a set of upper bits and lower bits) latched by the first latch circuit 82A and the second latch circuit 82B is input to the decoder 83, respectively. The decoder 83 performs decoding based on the upper bits and lower bits of the pixel data, and waveform sections SS11 to SS16, SS21 to SS26 constituting the first drive signal COM_A and the second drive signal COM_B (refer to FIG. 9). To generate selection data for selecting.

  The selection data in the present embodiment is generated separately for the first drive signal COM_A and the second drive signal COM_B. That is, the first selection data corresponding to the first drive signal COM_A is configured by 6-bit data corresponding to each of the first waveform portion SS11 to the sixth waveform portion SS16. Similarly, the second selection data corresponding to the second drive signal COM_B is also configured by 6-bit data corresponding to each of the first waveform portion SS21 to the sixth waveform portion SS26.

  The decoder 83 also receives a timing signal from the control logic 84. The control logic 84 functions as a timing signal generation unit together with the printer-side controller 60, and generates a timing signal based on the latch signal LAT and the change signals CH_A and CH_B. This timing signal is also generated for each drive signal COM. That is, the first timing signal TIM_A for the first drive signal COM_A and the second timing signal TIM_B for the second drive signal COM_B are generated. As shown in FIG. 9, in the first timing signal TIM_A, the timing pulse is generated in synchronization with the generation timing of the latch pulse and the change pulse for the first drive signal COM_A. The second timing signal TIM_B is generated in synchronization with the latch pulse and the change pulse for the second drive signal COM_B.

  The 6-bit selection data generated by the decoder 83 is sequentially output from the upper bit side at the timing defined by the timing pulse. The output selection data is input to the first level shifter 86A and the second level shifter 86B. That is, the first selection data is input to the first level shifter 86A in synchronization with the rising timing of the timing pulse included in the first timing signal TIM_A. The second selection data is input to the second level shifter 86B in synchronization with the rising timing of the timing pulse included in the second timing signal TIM-B. Further, the first all-on signal N_CHG_A for the first drive signal COM_A is input to the first level shifter 86A. The second level shifter 86B receives the second all-on signal N_CHG_B for the second drive signal COM_B.

  The first level shifter 86A and the second level shifter 86B function as voltage amplifiers. That is, when the selection data is [1] or when the first all-on signal N_CHG_A is on (H level), the first level shifter 86A is boosted to a voltage that can drive the first switch 87A. Output a signal. The second level shifter 86B is turned on when the selection data is [1] or when the second all-on signal N_CHG_B is on (H level), the voltage is increased to a voltage that can drive the second switch 87B. Output a signal. For example, when the first selection data is [1], an ON signal boosted to several tens of volts is output to the first switch 87A. Similarly, when the second selection data is [1], an ON signal boosted to several tens of volts is output to the second switch 87B.

  The first drive signal COM_A from the drive signal generation circuit 70 is applied to the input side of the first switch 87A, and the second drive signal COM_B is applied to the input side of the second switch 87B. A piezo element 417 is electrically connected to the common output side of the first switch 87A and the second switch 87B. The first switch 87A and the second switch 87B are switches provided for each generated drive signal COM. Then, the first drive signal COM_A and the second drive signal COM_B are selectively applied to the piezo element 417.

  The selection data controls the operation of the first switch 87A and the second switch 87B. That is, during a period in which the selection data input to the first switch 87A is [1], the first switch 87A is in a connected state, and the first drive signal COM_A is applied to the piezo element 417. Similarly, the second drive signal COM_B is applied to the piezo element 417 during a period in which the selection data input to the second switch 87B is [1]. The potential of the piezo element 417 is determined according to the applied first drive signal COM_A or second drive signal COM_B. On the other hand, during the period when the selection data input to the first switch 87A and the selection data input to the second switch 87B are both [0], the first switch 87A and the second switch 87B The electrical signal for operating the two switch 87B is not output.

=== About the operation when dots are formed and when dots are not formed ===
<Operation during dot formation>
FIG. 10 is a diagram for explaining pixel data (gradation value), a waveform portion selection pattern, and selection data. FIG. 11 is a diagram illustrating a waveform portion applied to the piezo element 417 during the formation of small dots, the formation of medium dots, and the formation of large dots. In this multi-gradation control, the operations of the first switch 87A and the second switch 87B are controlled based on the selection data generated by the decoder 83.

  First, the case of no dot formation (pixel data [00]) will be described. In this case, the decoder 83 generates first selection data [000000] and second selection data [000000] based on pixel data [00] indicating non-recording. The first selection data [000000] and the second selection data [000000] are output to the first switch 87A and the second switch 87B in order from the higher bit side at the timing (rising timing) when the timing signal becomes H level. Is done. Here, the first selection data is [000000], and the second selection data is also [000000]. For this reason, the waveform portions SS11 to SS16 of the first drive signal COM_A are not applied to the piezo element 417. Similarly, the waveform portions SS21 to SS26 of the second drive signal COM_B are not applied to the piezo element 417. As a result, the drive pulse PS is not applied to the piezo element 417, and no ink is ejected from the nozzle Nz.

  Next, the case of forming small dots (pixel data [01]) will be described. In this case, the decoder 83 generates first selection data [001000] and second selection data [000000] based on the pixel data [01] indicating the formation of small dots. As described above, the first selection data [000000] and the second selection data [000000] are sent to the first switch 87A and the second switch 87B in order from the higher bit side at the timing when the timing signal becomes H level. Is output. Here, the first selection data is [001000]. For this reason, the first drive signal COM_A is applied to the piezo element 417 during the period T3 as indicated by a thick line in FIG. That is, the third waveform portion SS13 is applied to the piezo element 417. On the other hand, the second selection data is [000000]. For this reason, the second drive signal COM_B is not applied to the piezo element 417. Accordingly, the drive pulse PS generated in the period T3 is applied to the piezo element 417, and an amount of ink corresponding to the small dot is ejected from the nozzle Nz. As a result, small dots are formed on the paper S.

  Next, the case of formation of medium dots (pixel data [10]) will be described. In this case, the decoder 83 generates first selection data [001000] and second selection data [010100] based on the pixel data [10] indicating the formation of medium dots. Then, when the first selection data [001000] is output to the first switch 87A, the first drive signal COM_A is applied to the piezo element 417 in the period T3. That is, the third waveform portion SS13 is applied to the piezo element 417 as indicated by a thick line in FIG. Further, when the second selection data [010100] is output to the second switch 87B, the second drive signal COM_B is applied to the piezo element 417 in the period T2 and the period T4. That is, as shown by a thick line in FIG. 11, the second waveform portion SS22 and the fourth waveform portion SS24 are applied to the piezo element 417. As a result, the drive pulse PS generated in the period T2, the drive pulse PS generated in the period T3, and the drive pulse PS generated in the period T4 are applied to the piezo element 417, and correspond to the medium dot from the nozzle Nz. A sufficient amount of ink is ejected. As a result, medium dots are formed on the paper S.

  Next, the case of large dot formation (pixel data [11]) will be described. In this case, the decoder 83 generates first selection data [101010] and second selection data [010101] based on the pixel data [11] indicating the formation of large dots. When the first selection data [101010] is output to the first switch 87A, the first drive signal COM_A is applied to the piezo element 417 in the period T1, the period T3, and the period T5, as shown by the thick lines in FIG. Is done. When the second selection data [010101] is output to the second switch 87B, the second drive signal COM_B is applied to the piezo element 417 in the period T2, the period T4, and the period T6, as shown by the thick line in FIG. Is done. Accordingly, the three drive pulses PS included in the first drive signal COM_A and the three drive pulses PS included in the second drive signal COM_B are applied to the piezo element 417, and an amount of ink corresponding to a large dot is generated from the nozzle Nz. Discharged. As a result, large dots are formed on the paper S.

<Operation when no dots are formed>
As operations when dots are not formed, there are a preliminary operation immediately after power-on, a CR operation, and a normal flushing operation. Here, the preliminary operation, the CR operation, and the normal flushing operation will be described.

<For preliminary operation>
FIG. 17 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during the preliminary operation as a reference example. The preliminary operation is an operation performed immediately after the power is turned on and a print command is input. Note that in the first drive signal COM_A in FIG. 17, only one micro-vibration pulse VP is drawn for convenience of explanation, but in reality, innumerable micro-vibration pulses VP are generated while moving to the flushing operation position. Generated continuously. In addition, although only one drive pulse PS is illustrated, innumerable continuous drive pulses PS are actually generated by the first drive signal generation unit 70A during the power flushing operation.

In a type of printer that ejects ink to form dots, the ink in the nozzles may be thickened or solidified when the power is turned on. In such a case, “wiping” is performed by wiping off the solidified ink on the nozzle surface with a cleaner (not shown). When wiping is performed, since the cleaner directly contacts the nozzle, the ink adhering to the cleaner enters the nozzle and mixes the colors. If ink mixes in and mixes colors, ink of an unexpected color is ejected from the nozzles, which is extremely inconvenient in image formation.
Therefore, when the power is turned on, after the nozzle surface is wiped, a power flushing operation is performed in which ink droplets are forcibly ejected and the mixed ink is discarded.

  16A and 16B are explanatory diagrams of a general flushing operation. 16A and 16B are views seen from the paper feed side of the printer 1. FIG. 16A is an explanatory diagram showing a stop position of the carriage CR before the dot formation process. FIG. 16B is an explanatory diagram of the flushing operation of the carriage CR.

  Before the power is turned on, the carriage CR is stopped at the stop position shown in FIG. 16A. Then, when the power is turned on and the power flushing operation in the preliminary operation is performed, the carriage CR is moved onto the ink receiving portion 701 (flushing operation position) shown in FIG. 16B. Then, wiping of the nozzle surface is performed, and ink droplets are ejected to the absorbing member 702 for absorbing ink.

  Incidentally, in the drive signal COM_A in the preliminary operation of the reference example shown in FIG. 17, the first drive signal COM_A includes a potential boost to the intermediate potential Vc, and a fine pulse VP and a drive pulse PS for driving the piezo element 417. However, the second drive signal COM_B maintains a constant potential of 0.6 (V). As described later, only the first drive signal COM_A is applied to the piezo element 417. Here, the first drive signal COM_A applied to the piezo element 417 will be described.

  When the power is turned on and the preliminary operation is started, the first drive signal generation circuit 70A boosts the potential of the first drive signal COM_A to the intermediate potential Vc that is a reference potential for ejecting ink droplets (startup). . A pulse is generated based on the intermediate potential Vc so that the piezo element 417 is driven. That is, the intermediate potential Vc can be said to be a pulse start potential.

The rate of increase in potential at startup is such a rate that ink is not ejected even when the first drive signal COM_A at startup is applied to the piezo element 417. Here, the potential of the first drive signal is raised so as to reach an intermediate potential Vc of 24 (V) in about 20 μs.

  The first drive signal COM_A is applied to the piezo element 417 from the start of startup. At this time, the first all-on signal N_CHG_A is output in order to apply the first drive signal COM_A to the piezo element 417. As a result, the potential at the time of startup for boosting to the intermediate potential Vc is applied to the piezo element 417.

  Next, the carriage CR starts to move from a predetermined position (FIG. 16A) when the power is turned on to a flushing operation position (FIG. 16B). In this period, the first drive signal generation circuit generates the fine vibration pulse VP. Then, the fine vibration pulse VP is applied to the piezo element 417, the thickened ink is stirred, or the solidified ink is melted by the non-solidified ink, and ink droplets are easily ejected in the subsequent flushing operation. This fine vibration pulse VP is applied to all the piezo elements 417. At this time, the first all-on signal N_CHG_A is output so as to apply only the first drive signal COM_A to the piezo element 417. In this way, the fine vibration pulse VP is applied to the piezo element 417 during the movement of the carriage CR.

  Next, in the flushing operation position, the first drive signal generation circuit 70A generates a drive pulse PS. This drive pulse PS is applied to all the piezo elements. Therefore, the first all-on signal N_CHG_A is used so that the first drive signal COM_A is applied to the piezo element 417. The first all-on signal N_CHG_A is output during the power flushing operation. As a result, the drive pulse PS is applied to the piezo element 417, and the ink droplet is discarded.

  When the power flushing is finished, the intermediate potential Vc of the first drive signal COM_A is lowered to 0.6 (V) (end down). Even at the time of end-down, the piezoelectric element 417 is driven by the displacement of the potential, and is lowered to 0.6 (V) in 20 μs so that an ink droplet is not ejected.

<About CR operation>
While the carriage CR is moved without performing the dot forming operation (when the CR operation is performed), the ink meniscus is vibrated slightly in order to prevent ink thickening. The fine vibration of the ink meniscus is performed by applying a fine vibration pulse VP to the piezo element 417.

  FIG. 18 shows a drive signal including a fine vibration pulse VP as a reference example. In the reference example illustrated in FIG. 18, the first drive signal generation unit 70A generates the first drive signal COM_A including the minute vibration pulse VP between the periods T1 to T6, and the second drive signal generation unit 70B includes the periods T1 to T1. The second drive signal COM_B that is a constant potential signal of 0.6 (V) is generated until T6. In the first drive signal COM_A, the intermediate potential Vc is set as the start potential of the fine vibration pulse VP. In order to apply the first drive signal COM_A to the piezo element 417, an all-on signal is used. Here, the first all-on signal N_CHG_A is output in all the periods T1 to T6. Thereby, the fine vibration pulse VP is applied to the piezo element 417 in each of the periods T1 to T6, and the ink meniscus is finely vibrated.

<About normal flushing>
The normal flushing operation means that when a predetermined time (9 seconds in this embodiment) elapses during the printing operation, the dot formation operation is temporarily interrupted, the carriage CR is moved to a predetermined position, and ink is discarded. It is an operation to make it possible. By doing so, it is possible to perform good image formation by discarding ink that thickens at predetermined intervals.

  At the time of dot formation, the carriage CR is on the paper S, and ink droplets are ejected from the nozzles. Then, when the predetermined time has passed and the timing for performing the normal flushing operation is reached, the dot forming operation is temporarily interrupted, and the carriage CR is moved to the flushing operation position shown in FIG. 16B.

  When the movement of the carriage CR is completed at the flushing operation position, ink is discarded. FIG. 19 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during normal flushing as a reference example. The illustrated first drive signal COM_A has a drive pulse PS for flushing in any of the periods T1, T2, T3, T4, T5, and T6. In the second drive signal COM_B, a constant potential of 0.6 (V) is maintained.

  The decoder 83 can change the selection data to be output by rewriting the register value of the control logic 84. At the time of normal flushing, the waveform selection pattern for large dot formation of the decoder is temporarily changed to that for normal flushing operation. During the normal flushing operation, the first selection data for forming large dots is changed to [111111]. Then, the second selection data is changed to [000000].

  During the normal flushing operation of the reference example, ink droplets are ejected at a relatively high speed of 21 kHz. When ink droplets are ejected from all nozzles at such a frequency, there is a risk that the supply of power will not be in time. Therefore, as shown below, in the reference example, the pixel data SI is sent so that the nozzles that eject ink are switched between the odd-numbered nozzles and the even-numbered nozzles every period T.

  For example, in the first cycle T, [1] is input to the first shift register 81A of the odd nozzle and [1] is input to the second shift register 81B of the odd nozzle so that ink droplets can be ejected from the odd nozzle. Thus, pixel data SI is sent. On the other hand, the pixel data SI is set such that [0] is input to the first shift register 81A of the even nozzle and [0] is input to the second shift register 81B of the even nozzle so as not to eject ink droplets from the even nozzle. Will be sent.

  Thus, when the pixel data [11] for large dot formation is sent, the decoder 83 of the odd nozzle generates the first selection data [111111] and the second selection data [000000]. When the first selection data [111111] is sequentially output from the upper bits to the first switch 87A, the first drive signal COM_A is applied to the piezo element 417 in the periods T1, T2, T3, T4, T5, and T6. The On the other hand, when the second selection data [000000] is sequentially output to the second switch 87B, the second drive signal COM_B is not applied to the piezo element 417 in any period.

  On the other hand, when the non-dot-formed pixel data [00] is sent, the even nozzle decoder 83 generates the first selection data [000000] and the second selection data [000000]. When the first selection data and the second selection data are sequentially output to the first switch 87A or the second switch 87B, the first drive signal COM_A and the second drive signal COM_B are supplied to the piezo element 417 in any period. Not applied.

In the next period T, [0] is input to the first shift register 81A of the odd nozzle and [0] is input to the second shift register 81B of the odd nozzle so as not to eject ink droplets from the odd nozzle. Pixel data SI is sent to. On the other hand, the pixel data SI is such that [1] is input to the first shift register 81A of the even nozzle and [1] is input to the second shift register 81B of the even nozzle so that ink droplets can be ejected from the even nozzle. Will be sent.
The operation of the decoder 83 at this time will be omitted because only the odd-numbered nozzles and the even-numbered nozzles are switched. However, no ink droplets are ejected from the odd-numbered nozzles, and ink droplets are output from the even-numbered nozzles. become.

  As described above, the pixel data SI sent to the shift registers of the odd-numbered nozzles and the even-numbered nozzles are repeatedly exchanged, whereby the ink droplets are alternately ejected between the odd-numbered nozzles and the even-numbered nozzles every period T. .

  During normal flushing, no PTS is generated because the carriage CR is stationary. Therefore, the timer PTS is used. That is, a latch signal is generated by the timer PTS, and ink droplets are alternately ejected from the odd and even nozzles for each latch signal. Here, the timer PTS is generated so that the flushing operation can be performed by ejecting ink at 21 kHz.

  So far, the operation of a general ink ejection type printer when forming dots and when not forming dots has been described. When the dot is not formed, that is, during the preliminary operation, the CR operation, and the normal flushing, an intermediate is performed so that only one first drive signal COM_A of the two drive signals can output a predetermined pulse. The voltage was boosted to the potential Vc, and the other second drive signal COM_B was a constant potential signal of 0.6 (V). In this case, when the switches 87A and 87B are simultaneously turned on due to the influence of noise or the like, the current generated by the potential difference between the first drive signal COM_A and the second drive signal COM_B generates the drive signal having the lower potential. There was a risk that it would flow into the circuit and destroy the circuit.

  In the present embodiment, the following drive signals are used, and the risk of circuit damage is reduced even if the switches 87A and 87B are simultaneously turned on due to noise or the like when dots are not formed.

=== Operation of this Embodiment ===
=== First Embodiment ===
<During preliminary operation>
FIG. 20 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B in the present embodiment. In the first drive signal COM_A and the second drive signal COM_B in FIG. 20, the same drive signal COM is generated at the same timing. Then, only the first drive signal COM_A is applied to the piezo element 417 during the preliminary operation. In FIG. 20, for convenience of explanation, only one fine vibration pulse VP is drawn in each of the first drive signal COM_A and the second drive signal COM_B, but in actuality while moving to the flushing operation position. Innumerable micro-vibration pulses VP are continuously generated at the same timing. Further, only one drive pulse PS is depicted in each of the first drive signal COM_A and the second drive signal COM_B, but in reality, innumerable drive pulses PS have the same timing during the power flushing operation. Is generated continuously.

  Next, start-up, fine vibration pulse VP, drive pulse PS, and end-down during the preliminary operation will be described. When the power is turned on and a print command is input, the first drive signal generator 70A and the second drive signal generator 70B boost the potential of each drive signal to the intermediate potential Vc at the same timing (startup). At this time, the first drive signal COM_A is applied to the piezo element 417. When generating the first drive signal COM_A and the second drive signal COM_B, the same DAC value is input to the first drive signal generation unit 70A and the second drive signal generation unit 70B at the same timing. The rate of increase in potential at start-up is set to be an intermediate potential of 24 (V) in about 20 μs.

  Next, in order to perform power flushing, the carriage CR starts to move to the flushing operation position (FIG. 16B). While the carriage CR moves to the position where flushing is performed, the first drive signal generation unit 70A and the second drive signal generation unit 70B generate the same fine vibration pulse VP at the same timing. The first all-on signal N_CHG_A is applied so that the fine vibration pulse VP of the first drive signal among the fine vibration pulses VP included in the first drive signal COM_A and the second drive signal COM_B is applied to all the piezoelectric elements 417. Is output. In this way, fine vibration of the ink meniscus is performed while the carriage CR is moving.

  When the carriage CR completes its movement to the flushing operation position, power flushing is started. During power flushing, both the first drive signal generator 70A and the second drive signal generator 70B generate the drive pulse PS at the same timing. The first all-on signal N_CHG_A is applied so that the driving pulse PS of the first driving signal COM_A among all the driving pulses PS included in the first driving signal COM_A and the second driving signal COM_B is applied to all the piezo elements 417. Is output. In this way, the drive pulse PS is applied to the piezo element 417 during power flushing, and ink droplets are discarded.

  When the power flushing is finished, the intermediate potential Vc of the first drive signal COM_A and the second drive signal COM_B is lowered to 0.6 (V) (end down). At the time of end-down, the voltage is lowered from the intermediate potential of 24 (V) of the first drive signal COM_A and the second drive signal COM_B to 0.6 (V) in 20 μs.

  During the preliminary operation of the reference example described above, the first drive signal COM_A included a predetermined pulse, whereas the second drive signal COM_B was a constant potential signal of 0.6 (V). On the other hand, in the first embodiment, the same drive signal as the first drive signal COM_A is set as the second drive signal COM_B. Thus, in the first embodiment, the potential difference between the first drive signal COM_A and the second drive signal COM_B is set to zero.

  As described above, in the preliminary operation when dots are not formed, the first drive signal and the second drive signal are set to the same signal, so that both the switch 87A and the switch 87B are turned on due to noise or the like. Even in this case, since the first drive signal COM_A and the second drive signal COM_B have the same potential, it is minimal that a current resulting from the potential difference flows into the first drive signal generation unit 70A or the second drive signal generation unit 70B. To the limit. And possibility that IC etc. which comprise these drive signal generation parts will be destroyed can be reduced.

<CR operation>
FIG. 21 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during the CR operation in the first embodiment. In the first embodiment, in the first drive signal generator 70A and the second drive signal generator 70B, the same micro-vibration pulse is generated at the same timing as shown in FIG. Then, only the first drive signal COM_A is applied to the piezo element 417. Note that boosting to the intermediate potential Vc is performed in the same manner as the startup described above.

  In order to apply the first drive signal COM_A to the piezo element 417, the first all-on signal N_CHG_A is used. As a result, during the CR operation, the fine vibration pulse VP of the first drive signal COM_A is applied to the piezo element 417, and the ink meniscus is finely vibrated.

  As described above, in the CR operation, the first drive signal COM_A and the second drive signal COM_B are set to the same signal, so that both the switch 87A and the switch 87B are turned on due to noise or the like. In addition, since the first drive signal COM_A and the second drive signal COM_B have the same potential, it is possible to minimize the flow of the current resulting from the potential difference into the first drive signal generation unit 70A or the second drive signal generation unit 70B. Can do. And possibility that IC etc. which comprise these production | generation parts will be destroyed can be reduced.

<Normal flushing>
FIG. 22 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during normal flushing in the first embodiment. The exemplified first drive signal COM_A includes a flushing drive pulse PS in any of the periods T1, T2, T3, T4, T5, and T6. The second drive signal COM_B also includes the drive pulse PS in any of the periods T1, T2, T3, T4, T5, and T6, similarly to the first drive signal. That is, the same drive pulse PS is generated at the same timing in the first drive signal and the second drive signal.

  The waveform selection method in the first embodiment is the same as that in the normal flushing operation of the reference example. That is, the decoder 83 in the first embodiment can change the selection data in the same manner as in the normal flushing operation described above. In the first embodiment, the waveform selection pattern for large dot formation of the decoder is temporarily changed during the normal flushing operation. At the time of normal flushing, the first selection data for forming large dots is changed to [111111]. Then, the second selection data is changed to [000000].

  Similarly to the case of the reference example, the pixel data SI is sent so that the odd-numbered nozzles and the even-numbered nozzles can alternately eject ink droplets every period T. Since the operation of the decoder 83 at this time is the same as that in the reference example, the description is omitted. In this way, ink droplets are ejected during the normal flushing operation.

  In the first embodiment, the second drive signal COM_B is not applied to the piezo element 417 when no dots are formed. Nevertheless, the reason why the fine vibration pulse VP and the drive pulse PS are included in the second drive signal COM_B is that the potential difference from the first drive signal COM_A is zero.

  As described above, even when the switch 87A and the switch 87B are both turned on by noise or the like by making the first drive signal and the second drive signal the same during the normal flushing operation. Since the first drive signal COM_A and the second drive signal COM_B have the same potential, it is possible to minimize the flow of the current resulting from the potential difference into the first drive signal generation unit 70A or the second drive signal generation unit 70B. it can. And possibility that IC etc. which comprise these production | generation parts will be destroyed can be reduced.

=== Second Embodiment ===
<During preliminary operation>
In the second embodiment, as in the first embodiment, the same drive signal is generated by the first drive signal COM_A and the second drive signal COM_B during the preliminary operation. However, in the second embodiment, the first drive signal COM_A and the second drive signal COM_B are alternately selected at a predetermined cycle and applied to the piezo element 417.

  FIG. 23 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during the preliminary operation in the second embodiment. Although only two each of the micro-vibration pulse VP and the driving pulse PS for flushing are drawn, infinite (however, even number) pulses are continuously generated at the same timing. Then, the first drive signal COM_A and the second drive signal COM_B are exchanged for each pulse when the fine vibration pulse and the drive pulse PS are generated. The method for generating the first drive signal COM_A and the second drive signal COM_B in the second embodiment is substantially the same as in the first embodiment. That is, the same DAC value is input to the first drive signal generation unit 70A and the second drive signal generation unit 70B at the same timing so that the first drive signal COM_A and the second drive signal COM_B become the same drive signal.

  Next, start-up, fine vibration pulse VP, drive pulse PS, and end-down during the preliminary operation of the second embodiment will be described. When the power is turned on and a print command is input, the first drive signal generator 70A and the second drive signal generator 70B set the potential of the drive signal COM to the intermediate potential Vc at the same timing as in the first embodiment. Boost the pressure. At this time, the first all-on signal N_CHG_A is turned on, and the first drive signal COM_A is applied to the piezo element 417 as an actuator.

  Next, while the carriage CR moves to the flushing operation position, both the first drive signal generation unit 70A and the second drive signal generation unit 70B generate the fine vibration pulse VP. In the second embodiment, the fine vibration pulse VP of the first drive signal COM_A and the fine vibration pulse VP of the second drive signal COM_B are alternately applied to the piezo element 417. In the second embodiment, the first all-on signal N_CHG_A and the fine vibration pulse VP of the first drive signal COM_A and the fine vibration pulse VP of the second drive signal COM_B are alternately applied to the piezo element 417. The second all-on signal N_CHG_B is alternately output.

  When the carriage CR completes its movement to the flushing operation position, power flushing is started. During the power flushing, both the first drive signal generator 70A and the second drive signal generator 70B generate the flushing drive pulse PS at the same timing. Again, the drive pulse PS of the first drive signal COM_A and the drive pulse PS of the second drive signal COM_B are alternately applied to the piezo element 417. In order to alternately apply the driving pulse PS of the first driving signal and the driving pulse PS of the second driving signal to the piezo element 417, the first all-on signal N_CHG_A and the second all-on signal N_CHG_B are alternately output. Is done.

  When the power flushing is finished, the intermediate potential Vc of the first drive signal COM_A and the second drive signal COM_B is lowered to 0.6 (V).

  In the second embodiment, the first drive signal COM_A and the second drive signal COM_B are alternately applied to the piezo element 417, but the drive signal similar to the drive signal of the first drive signal COM_A is the same as in the first embodiment. It is generated as the second drive signal COM_B. In this way, the potential difference between the first drive signal COM_A and the second drive signal COM_B is set to zero. In this way, even when the switch 87A and the switch 87B are simultaneously turned on due to noise or the like when dots are not formed, the first drive signal and the second drive signal are at the same potential. Therefore, it is possible to minimize the current generated from the potential difference from flowing into the first drive signal generation unit 70A or the second drive signal generation unit 70B. And possibility of destroying IC etc. which comprise these drive signal generation parts can be reduced.

<CR operation>
FIG. 24 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during the CR operation in the second embodiment. Also in the second embodiment, the same micro-vibration pulse VP is generated at the same timing as shown in FIG. 24 in the first drive signal generator 70A and the second drive signal generator 70B. Then, the first drive signal COM_A and the second drive signal COM_B are alternately applied to the piezo element 417 for each pulse.

  The first all-on signal N_CHG_A and the second all-on signal N_CHG_B are alternately output so that the first drive signal COM_A and the second drive signal COM_B are alternately applied to the piezo element 417. Thereby, during the CR operation, the fine vibration pulse VP is applied to the piezo element 417, and the fine vibration of the ink meniscus is performed.

  Also during the CR operation in the second embodiment, as in the first embodiment, the first drive signal COM_A and the second drive signal COM_B are the same signal, and the potential difference between them is zero. By doing so, the first drive signal and the second drive signal are at the same potential even when the switch 87A and the switch 87B are simultaneously turned on during the CR operation due to the influence of noise or the like. Thus, it is possible to minimize the current generated from the potential difference from flowing into the first drive signal generation unit 70A or the second drive signal generation unit 70B. And possibility of destroying IC etc. which comprise these drive signal generation parts can be reduced.

<Normal flushing>
FIG. 22 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during normal flushing. Since this figure has been described in the first embodiment, the description is omitted here, but the same drive pulse PS is generated at the same timing in the first drive signal COM_A and the second drive signal COM_B.

  During the normal flushing operation in the second embodiment, the drive pulses PS of the first drive signal COM_A and the second drive signal COM_B are alternately applied to the piezo elements 417 for each pulse. Specifically, the same pixel data [11] as when forming a large dot is sent, and based on this, the drive pulse PS is applied to the piezo element 417.

  The decoder 83 generates first selection data [101010] and second selection data [010101] based on the pixel data [11] indicating the formation of large dots. Then, when the first selection data [101010] is output to the first switch 87A, the first drive signal COM_A is applied to the piezo element 417 in the period T1, the period T3, and the period T5. When the second selection data [010101] is output to the second switch 87B, the second drive signal COM_B is applied to the piezo element 417 in the periods T2, T4, and T6. Thus, the drive pulse PS of the first drive signal COM_A and the drive pulse PS of the second drive signal COM_B are alternately applied to the piezo element 417 from T1 to T6, and ink droplets are continuously ejected to normal. A flushing operation is performed.

  Also in the second embodiment, as in the first embodiment, the first drive signal COM_A and the second drive signal COM_B are the same signal, and the potential difference between them is zero. In this way, even when the switch 87A and the switch 87B are simultaneously turned on due to noise or the like when dots are not formed, the first drive signal and the second drive signal are at the same potential. Therefore, it is possible to minimize the current generated from the potential difference from flowing into the first drive signal generation unit 70A or the second drive signal generation unit 70B. And possibility of destroying IC etc. which comprise these generating parts can be reduced.

=== Third Embodiment ===
FIG. 25 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during the preliminary operation in the third embodiment. For convenience of explanation in FIG. 25, only one micro-vibration pulse VP of the first drive signal COM_A is drawn, but in fact, an infinite number of micro-vibration pulses VP are generated continuously while the carriage CR is moving. . Further, although only one drive pulse PS is drawn in the first drive signal COM_A, an infinite number of drive pulses PS are actually generated continuously.

  In FIG. 25, the first drive signal is common to the first drive signal COM_A in the first embodiment. On the other hand, the second drive signal COM_B is boosted to an intermediate potential Vc having the same potential as the first drive signal at start-up, but maintains the intermediate potential Vc during the micro-vibration operation and during the power flushing. In the preliminary operation, only the first drive signal COM_A is applied to the piezo element 417.

  Next, start-up, fine vibration pulse VP, drive pulse PS, and end-down during the preliminary operation of the third embodiment will be described. When the power is turned on and a print command is input, the first drive signal generation unit 70A and the second drive signal generation unit 70B boost the drive signal potential to the intermediate potential Vc at the same timing as in the first embodiment. . At this time, the first all-on signal N_CHG_A is turned on, and the first drive signal COM_A is applied to the piezo element 417.

  Next, while the carriage CR is moved to the flushing operation position, the first drive signal generation unit 70A generates the fine vibration pulse VP, and the second drive signal generation unit 70A has a constant potential of the intermediate potential Vc. To maintain. In order to apply the first driving signal COM_A to the piezo element 417, the first all-on signal N_CHG_A is output.

  When the carriage CR completes its movement to the flushing operation position, power flushing is started. During the power flushing, the first drive signal generator 70A generates the drive pulse PS, and the second drive signal generator 70B maintains the constant potential of the intermediate potential Vc. Then, the first all-on signal N_CHG_A is output so that the drive pulse PS of the first drive signal COM_A is applied to all the piezo elements 417.

  When the power flushing is completed, the intermediate potential Vc of the first drive signal COM_A and the second drive signal COM_B is lowered to 0.6 (V).

  In the preliminary operation of the reference example described above, the first drive signal COM_A includes a predetermined pulse, whereas the second drive signal is a constant potential signal of 0.6 (V). On the other hand, in the third embodiment, a constant potential signal having the same potential as the intermediate potential Vc of the first drive signal COM_A is generated as the second drive signal COM_B. In this way, the potential difference between the first drive signal COM_A and the second drive signal COM_B is reduced.

  Therefore, even if the switch 87A and the switch 87B are turned on due to a malfunction, the first drive signal COM_A and the second drive signal COM_B are more effective than when the second drive signal is kept at a constant potential of 0.6 (V). Since the potential difference is small, it is possible to reduce the risk that the current generated from the potential difference damages the IC that constitutes the first drive signal generation unit 70A or the second drive signal generation unit 70B.

<CR operation>
FIG. 26 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during the CR operation in the third embodiment. In the third embodiment, the first drive signal generation unit 70A generates a fine vibration pulse VP, and the second drive signal generation unit 70B generates a constant potential signal having an intermediate potential Vc. Then, the first all-on signal N_CHG_A is output so that only the first drive signal COM_A is applied to the piezo element 417.

  In the third embodiment, a constant potential signal having the same potential as the intermediate potential Vc of the first drive signal COM_A is generated as the second drive signal COM_B. In this way, the potential difference between the first drive signal COM_A and the second drive signal COM_B is reduced. Therefore, even if the switch 87A and the switch 87B are turned on due to a malfunction, the first drive signal COM_A and the second drive signal COM_B are more effective than when the second drive signal is kept at a constant potential of 0.6 (V). Since the potential difference is small, it is possible to reduce the risk that the current generated from the potential difference damages the IC that constitutes the first drive signal generation unit 70A or the second drive signal generation unit 70B.

<Normal flushing>
FIG. 27 is a diagram illustrating the first drive signal COM_A and the second drive signal COM_B during normal flushing in the third embodiment. The first drive signal COM_A in FIG. 27 includes a drive pulse PS for flushing in any of the periods T1, T2, T3, T4, T5, and T6. On the other hand, the second drive signal COM_B maintains a constant potential of the intermediate potential Vc in the periods T1 to T6.

  The waveform selection method in the third embodiment is the same as that in normal flushing in the reference example. That is, the decoder 83 in the third embodiment can change the selection data in the same manner as in the normal flushing described above. In the third embodiment, the waveform selection pattern for large dot formation of the decoder is changed during normal flushing. At the time of normal flushing, the first selection data for forming large dots is changed to [111111]. Then, the second selection data is changed to [000000].

  Similarly to the case of the reference example, the pixel data SI is sent so that the odd-numbered nozzles and the even-numbered nozzles can alternately eject ink droplets every period T. Since the operation of the decoder 83 at this time is the same as that in the reference example, the description is omitted. In this way, ink droplets are ejected during the normal flushing operation.

  As described above, in this embodiment, when dots are not formed, the potential difference between the intermediate potential Vc of the first drive signal COM_A for dot non-formation and the constant potential signal of the second drive signal COM_B is the first drive signal COM_A and the first potential. It is smaller than the maximum potential difference with the two drive signals COM_B. That is, the potential difference between them is smaller than when the second drive signal is kept at a constant potential of 0.6 (V). Therefore, even when the switch 87A and the switch 87B are turned on at the same time due to the influence of noise or the like, the current generated by the potential difference between them causes the second drive signal to have a constant potential of 0.6 (V). Less than when kept. Therefore, even if the switch 87A and the switch 87B are turned on due to a malfunction, the current due to the potential difference is greater than that when the second drive signal is kept at a constant potential of 0.6 (V). Alternatively, it is possible to reduce the risk of damaging the IC constituting the second drive signal generation unit 70B.

<Number of drive signals used>
In the above description, two types of drive signals, the first drive signal COM_A and the second drive signal COM_B, have been described. However, the number of drive signals is not limited to two. By providing a further drive signal generator, the drive signal COM applied to the piezo element 417 can be selected from a larger number of drive signals.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the head>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.
In the above-described embodiment, the head is provided on the carriage. However, the head may be provided in an ink cartridge that is detachable from the carriage.

=== Summary ===
(1) First Embodiment and Second Embodiment A printer 1 as a liquid ejection apparatus in the above-described embodiments includes a first drive signal generation unit 70A and a second drive signal generation unit 70B that generate drive signals, and a drive signal. And a piezo element 417 as a liquid ejecting section that is driven according to the above and can eject ink droplets. The printer 1 also includes a printer-side controller 60 that causes the first drive signal generation unit 70A and the second drive signal generation unit 70B to generate drive signals. Furthermore, the printer 1 selects one of the drive signals generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B, and serves as a control unit that drives the piezo element 417 by the selected drive signal. A head controller HC is provided. That is, the printer controller 60 and the head controller HC constitute a control unit.

  Then, the printer-side controller 60 generates a dot formation drive signal in the first drive signal generation unit 70A and the second drive signal generation unit 70B when forming a dot by causing ink droplets to land on the paper S to form a dot. Let Further, the printer-side controller 60, when the piezo element 417 is driven by the drive signal but does not form a dot but does not form a dot, outputs the same drive signal for non-dot formation to the first drive signal generator 70A and the second drive. The signal generator 70B generates the signal.

In this way, even when the switch for switching the input of the drive signal is turned on at the same time, the drive signal generated by the first drive signal generation circuit 70A and the drive generated by the second drive signal generation circuit 70B Since the potential difference from the signal is 0, even if the switches for switching the input of the drive signal are turned on at the same time, the circuit may be damaged due to the current generated from the potential difference flowing into the circuit with the lower potential. Can be reduced.
However, only two generation circuits of the first drive signal generation circuit 70A and the second drive signal generation unit 70B are described here, but a configuration including more drive signal generation circuits may be employed. At this time, the drive signals generated by these drive signal generation circuits when dots are not formed are the same drive signal.

(2) For example, when the printer 1 is not forming dots, the head controller HC selects the first drive signal COM_A from the first drive signal generator 70A.
Thus, although only one drive signal is selected when dots are not formed, the drive waveforms of the first drive signal generation unit 70A and the second drive signal generation unit 70B are the same. Even when they are turned on at the same time, the potential difference between the two can be set to 0, and the possibility of circuit damage due to the current resulting from the potential difference flowing into the lower potential circuit can be reduced.

(3) Further, at the time of dot non-formation, the head controller HC outputs the first drive signal COM_A from the first drive signal generator 70A and the second drive signal COM_B from the second drive signal generator 70B to a predetermined level. Select alternately by period.
As described above, when the dots are not formed, the first drive signal COM_A and the second drive signal COM_B are alternately selected at predetermined intervals, but the first drive signal COM_A and the second drive signal COM_B are the same drive signal. Therefore, the potential difference between the two is set to 0, and the possibility of damage to the circuit due to the current resulting from the potential difference flowing into the circuit with the lower potential can be reduced.

(4) The head controller HC also includes a first drive signal generator 70B provided between the first drive signal generator 70B and the piezo element 417 in order to select the first drive signal COM_A from the first drive signal generator 70A. A switch 87A and a second switch 87B provided between the second drive signal generator 70B and the piezo element 417 for selecting the second drive signal 70B from the second drive signal generator 70B are included.
When the two switches 87A and 87B are turned on at the same time, the current flows into one of the drive signal generation units due to the potential difference between the first drive signal COM_A and the second drive signal COM_B, and the ICs and the like constituting them are damaged. There was a risk of causing it. However, in the first and second embodiments, the first drive signal COM_A and the second drive signal COM_B are the same drive signal at the time of dot formation. Therefore, the potential difference between the two becomes 0, and the possibility of damage to the circuit due to the current resulting from the potential difference flowing into the circuit with the lower potential can be reduced.

(5) Further, when no dots are formed, the ink droplets in the head 41 are stirred.
In this way, even when the switch for switching the drive signals is turned on at the same time during the fine vibration operation of the ink meniscus, the potential difference between the two is set to 0 and the current resulting from the potential difference flows into the circuit with the lower potential. This can reduce the possibility of circuit damage.

(6) In addition, a carriage CR that moves the head unit 40 is further provided, and when the dots are not formed, the carriage CR moves the head unit 40 without ejecting ink droplets.
In this way, even when the switches for switching the drive signals are simultaneously turned on during the ink meniscus microvibration operation during the movement of the carriage CR, the potential difference between the two is set to 0 and the current resulting from the potential difference is the potential. The possibility of circuit damage due to flowing into the lower circuit can be reduced.

(7) Further, when no dots are formed, it is a flushing operation in which ink droplets are not landed on the paper S although ink droplets are ejected. This flushing operation includes the aforementioned power flushing and normal flushing.
By doing this, even when the switch for switching the drive signal is turned on at the same time during the flushing operation for discarding the thickened ink droplets for good image formation, the potential difference between them is set to 0. Therefore, the possibility of circuit breakage due to the current generated in the circuit flowing into the circuit having the lower potential can be reduced.

(8) Further, according to the liquid ejecting apparatus including all of the above-described components, the effects of the present invention can be achieved most effectively because almost all the effects described above can be achieved.

(9) Further, the printer 1 according to the third embodiment is driven according to a pulse included in the drive signal and the first drive signal generation unit 70A and the second drive signal generation unit 70B that generate the drive signal. A dischargeable piezo element 417 and a liquid discharge unit. The printer 1 also includes a printer-side controller 60 that causes the first drive signal generation unit 70A and the second drive signal generation unit 70B to generate drive signals. Further, the printer 1 selects one of the drive signals generated by the first drive signal generator 70A and the second drive signal generator 70B, and drives the piezo element 417 by the selected drive signal. Is provided.

  The printer-side controller 60 causes the first drive signal generation unit 70A and the second drive signal generation unit 70B to generate dot formation drive signals at the time of dot formation in which ink droplets are landed on the paper S to form dots. In addition, the printer-side controller 60 causes the first drive signal generation unit 70A to generate a drive signal for non-dot formation when the piezo element 417 is driven by a motion signal but does not form a dot, and generates a non-dot formation drive signal. The signal is generated by the second drive signal generator 70B.

The potential difference between the pulse start potential (intermediate potential Vc) included in the dot non-formation drive signal and the constant potential signal is smaller than the maximum potential difference between the start potential and the potential of the dot non-formation drive signal. .
In this way, even when the switch for switching the input of the drive signal is turned on at the same time, the potential difference between the drive signals is reduced, so that the current resulting from the potential difference can also be reduced. Can reduce the possibility of the circuit being destroyed.

(10) For example, the constant potential signal generated by the second drive signal generation unit 70A is a constant potential signal having the same potential as the pulse start potential.

(11) In the above-described embodiment, the first drive signal and the second drive signal, which are the same drive signals for dot non-formation, are generated when dots are not formed, and dot formation is performed when dots are formed. Disclosed is a liquid ejection method for generating a first drive signal and a second drive signal for use, selecting either the first drive signal or the second drive signal, and applying the selected drive signal to the liquid ejection unit. Needless to say.

(12) Furthermore, the above-described embodiment generates a first drive signal for dot non-formation and a second drive signal that is a constant potential signal when dots are not formed, and is used for dot formation when dots are formed. A first drive signal and a second drive signal are generated, and either the first drive signal or the second drive signal is selected, and the selected drive signal is applied to the liquid ejection unit. The potential difference between the start potential of the pulse included in the first drive signal for non-dot formation and the constant potential signal is smaller than the maximum potential difference between the start potential and the potential of the first drive signal for non-dot formation. Needless to say, there is a disclosure of a method for driving the liquid ejection unit.

It is a figure for demonstrating the structure of a printing system. FIG. 3 is a diagram for explaining a configuration of a computer and a printer. FIG. 3A is a diagram illustrating the configuration of the printer, and FIG. 3B is a side view for explaining the configuration of the printer. 4A is a cross-sectional view for explaining the structure of the head, and FIG. 4B is a view for explaining the arrangement of the nozzle rows. FIG. 5A is a block diagram illustrating the configuration of the drive signal generation circuit, and FIG. 5B is a block diagram illustrating the configuration of the first waveform generation circuit. It is a figure for demonstrating the operation | movement which drops the output voltage of a 1st current amplifier circuit from voltage V1 to V4. FIG. 7A is a diagram for explaining a configuration of a current amplifier circuit, and FIG. 7B is an explanatory diagram of a configuration of two transistor pairs and a heat sink. It is a block diagram explaining the structure of a head control part. It is a figure which shows a 1st drive signal and a 2nd drive signal. It is a figure explaining pixel data (gradation value), the selection pattern of a waveform part, and selection data. It is explanatory drawing of the signal applied to a piezo element. It is the figure which showed schematically the structure of the linear encoder. It is the figure which showed the structure of the detection part typically. It is a figure for demonstrating the relationship of the timing of PTS, a latch signal, and a change signal. It is a flowchart for demonstrating printing operation. FIG. 16A is an explanatory diagram illustrating a stop position of the carriage CR before the dot formation process, and FIG. 16B is an explanatory diagram of a flushing operation of the carriage CR. It is a figure for explaining the 1st drive signal and the 2nd drive signal at the time of preliminary operation as a reference example. It is a figure which shows the drive signal containing the fine vibration pulse VP as a reference example. It is a figure which shows the 1st drive signal and the 2nd drive signal at the time of the normal flushing as a reference example. It is a figure which shows the 1st drive signal and 2nd drive signal at the time of the preliminary | backup operation | movement in 1st Embodiment. It is a figure which shows the 1st drive signal and 2nd drive signal at the time of CR operation | movement in 1st Embodiment. It is a figure which shows the 1st drive signal and the 2nd drive signal at the time of the normal flushing in 1st Embodiment and 2nd Embodiment. It is a figure which shows the 1st drive signal and 2nd drive signal at the time of the preliminary | backup operation | movement in 2nd Embodiment. It is a figure which shows the 1st drive signal and 2nd drive signal at the time of CR operation | movement in 2nd Embodiment. It is a figure which shows the 1st drive signal and 2nd drive signal at the time of the preliminary | backup operation | movement in 3rd Embodiment. It is a figure which shows the 1st drive signal and 2nd drive signal at the time of CR operation | movement in 3rd Embodiment. It is a figure which shows the 1st drive signal and the 2nd drive signal at the time of the normal flushing in 3rd Embodiment.

Explanation of symbols

1 printer, 20 paper transport mechanism, 21 paper feed roller, 22 transport motor,
23 transport roller, 24 platen, 30 carriage moving mechanism,
31 Carriage motor, 32 guide shaft, 33 timing belt,
34 drive pulley, 35 driven pulley, 40 head unit, 41 head,
50 detector groups, 51 linear encoder, 52 rotary encoder,
53 Paper detector, 54 Paper width detector, 60 Printer side controller,
61 interface unit, 62 CPU, 63 memory, 64 control unit,
70 drive signal generation circuit, 70A first drive signal generation unit,
70B second drive signal generation unit, 71A first waveform generation circuit,
71B second waveform generation circuit, 72A first current amplification circuit, 72B second current amplification circuit,
81A first shift register, 81B second shift register,
82A first latch circuit, 82B second latch circuit, 83 decoder,
84 control logic, 86A first level shifter, 86B second level shifter,
87A first switch, 87B second switch, 100 printing system,
110 computer, 120 display device, 130 input device,
140 recording / reproducing apparatus, 111 host-side controller, 112 interface unit,
113 CPU, 114 memory, 417 piezo element CTR controller board, CR carriage, HC head controller

Claims (12)

(1) a first drive signal generation unit and a second drive signal generation unit that generate a drive signal;
(2) a liquid ejection unit that is driven according to the drive signal and capable of ejecting liquid droplets;
(3) Either of the drive signals generated by the first drive signal generator and the second drive signal generator while causing the first drive signal generator and the second drive signal generator to generate a drive signal. A control unit that drives the liquid ejection unit according to the selected drive signal,
At the time of dot formation in which the liquid droplet is landed on a medium to form a dot, a drive signal for dot formation is generated in the first drive signal generation unit and the second drive signal generation unit,
When the liquid ejection unit is driven by the drive signal but the dots are not formed, the same dot non-formation drive signal is sent to the first drive signal generation unit and the second drive signal generation unit. A control unit to generate,
A liquid ejection apparatus comprising: The liquid ejection device according to claim 1,
The liquid ejecting apparatus, wherein when the dots are not formed, the control unit selects a signal from the first drive signal generation unit. The liquid ejection device according to claim 1,
When the dots are not formed, the control unit alternately selects a drive signal from the first drive signal generation unit and a drive signal from the second drive signal generation unit at a predetermined cycle. The liquid ejection device according to any one of claims 1 to 3,
The controller is
A first switch provided between the first drive signal generation unit and the liquid ejection unit to select a drive signal from the first drive signal generation unit;
A second switch provided between the second drive signal generation unit and the liquid ejection unit to select a drive signal from the second drive signal generation unit;
A liquid ejection apparatus comprising: The liquid ejection device according to any one of claims 1 to 3,
The liquid droplet ejection device, which is a time when the liquid droplets are agitated in the liquid ejection unit when the dots are not formed. A liquid ejection apparatus according to any one of claims 1 to 3,
A moving mechanism for moving the liquid discharge unit;
The liquid droplet ejecting apparatus, wherein the dot is not formed when the moving mechanism moves the liquid ejecting unit without ejecting a liquid droplet. The liquid ejection device according to any one of claims 1 to 3,
The liquid ejecting apparatus, which is a flushing operation in which the liquid droplets are not landed on the medium when the dots are not formed, although the liquid droplets are ejected. (1) a first drive signal generation unit and a second drive signal generation unit that generate a drive signal;
(2) a liquid ejection unit that is driven according to the drive signal and capable of ejecting liquid droplets;
(3) Either of the drive signals generated by the first drive signal generator and the second drive signal generator while causing the first drive signal generator and the second drive signal generator to generate a drive signal. A control unit that drives the liquid ejection unit according to the selected drive signal,
At the time of dot formation in which the liquid droplet is landed on a medium to form a dot, a drive signal for dot formation is generated in the first drive signal generation unit and the second drive signal generation unit,
When the liquid ejection unit is driven by the drive signal but the dots are not formed, the same dot non-formation drive signal is sent to the first drive signal generation unit and the second drive signal generation unit. A control unit to generate,
A moving mechanism for moving the liquid ejection part;
With
The controller is
A first switch provided between the first drive signal generation unit and the liquid ejection unit to select a drive signal from the first drive signal generation unit;
A second switch provided between the second drive signal generation unit and the liquid ejection unit to select a drive signal from the second drive signal generation unit;
When the dots are not formed, the control unit selects a signal from the first drive signal generation unit,
When the dots are not formed, it is a stirring operation of the liquid droplets in the liquid discharge unit,
When the dot is not formed, it is a time when the moving mechanism is moving the liquid discharge unit without discharging a liquid drop,
The liquid ejecting apparatus, which is a flushing operation in which the liquid droplets are not landed on the medium when the dots are not formed, although the liquid droplets are ejected. (1) a first drive signal generation unit and a second drive signal generation unit that generate a drive signal;
(2) a liquid ejection unit that is driven in accordance with a pulse included in the drive signal and is capable of ejecting a liquid droplet;
(3) Either of the drive signals generated by the first drive signal generator and the second drive signal generator while causing the first drive signal generator and the second drive signal generator to generate a drive signal. A control unit that drives the liquid ejection unit according to the selected drive signal,
At the time of dot formation in which the liquid droplet is landed on a medium to form a dot, a drive signal for dot formation is generated in the first drive signal generation unit and the second drive signal generation unit,
When the liquid ejection unit is driven by the drive signal but the dot is not formed, the dot non-formation drive signal is generated by the first drive signal generation unit and the constant potential signal is generated by the second drive. A control unit for generating the signal generation unit;
And the potential difference between the start potential of the pulse included in the drive signal for non-dot formation and the constant potential signal is smaller than the maximum potential difference between the start potential and the potential of the drive signal for non-dot formation Liquid discharge device. The liquid ejection device according to claim 9, wherein
The liquid ejection apparatus, wherein the constant potential signal generated by the second drive signal generation unit is a constant potential signal having the same potential as the start potential of the pulse. (1) generating a first drive signal and a second drive signal which are the same drive signals for non-dot formation at the time of non-dot formation;
(2) generating a first drive signal and a second drive signal for dot formation at the time of dot formation;
(3) selecting either the first drive signal or the second drive signal;
(4) applying the selected drive signal to the liquid ejection unit;
A method for driving a liquid ejection unit including: (1) generating a first drive signal for dot non-formation and a second drive signal that is a constant potential signal at the time of dot non-formation;
(2) generating a first drive signal and a second drive signal for dot formation at the time of dot formation;
(3) selecting either the first drive signal or the second drive signal;
(4) applying the selected drive signal to the liquid ejection unit;
And the potential difference between the start potential of the pulse included in the first drive signal for non-dot formation and the constant potential signal is the maximum between the start potential and the potential of the first drive signal for non-dot formation A method for driving the liquid ejection unit, which is smaller than the potential difference.

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