JP4892902B2 - Printing apparatus, printing method, program, and printing system - Google Patents

Description

  The present invention relates to a printing apparatus, a printing method, a program, and a printing system.

As a printing apparatus that prints an image on a medium, one that selectively applies a plurality of drive signals to one piezoelectric element is proposed. For example, a printing apparatus has been proposed in which a plurality of types of drive pulses with different amounts of ejected ink are divided into two drive signals, and these drive pulses are selectively applied to the piezo elements (for example, patents). See reference 1.) In addition, a printing apparatus has been proposed in which a drive pulse used when forming the maximum dot is included in one drive signal to increase the ink ejection frequency when forming the maximum dot (for example, Patent Document 2). See). These printing apparatuses are provided with a plurality of drive signal generation units that generate drive signals.
JP 2000-52570 A JP 2003-246086 A

As described above, when a plurality of drive signal generation units are provided in the printing apparatus, even if the same drive signal is generated by each drive signal generation unit, ink that is ejected due to variations in characteristics of the drive signal generation units. Variation in quantity occurs. As a result, the image quality of the printed image may deteriorate.
Therefore, an object of the present invention is to suppress a decrease in image quality of a printed image even if the characteristics of the respective drive signal generation units vary.

The main invention for achieving the above object is as follows: (A) an element driven to form a dot; (B) a drive signal for driving the element; and generating the drive signal as a first signal line. And (C) generating a drive signal for driving the element that can be driven by the drive signal generated by the first drive signal generation unit, and outputting the drive signal to the second drive signal generation unit A second drive signal generation unit for transmitting to the signal line; and (D) when forming a dot of a predetermined size at a certain timing, the first drive signal generation unit generates a first drive signal, and at another timing, the When forming dots of a predetermined size, the second drive signal generation unit generates the first drive signal, and selects from the drive signal of the first signal line and the drive signal of the second signal line Applied to the element And (E) a printing apparatus having a controller for controlling driving of the element, wherein (F) the printing apparatus forms dots on the medium while changing a relative position between the element and the medium. And (G) the controller drives the first drive signal generation unit that generates the first drive signal during the dot formation operation. The printing apparatus is characterized in that the signal generation unit is changed to the second drive signal generation unit.

  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.

(A) an element driven to form a dot;
(B) a first drive signal generation unit that generates a drive signal for driving the element;
(C) a second drive signal generation unit that generates a drive signal for driving the element;
(D) When forming dots of a predetermined size at a certain timing, the first drive signal generator generates a first drive signal;
A controller that generates the first drive signal in the second drive signal generation unit when forming the dot of the predetermined size at another timing;
A printing apparatus having (E),
(F) The printing apparatus alternately repeats a dot forming operation for forming dots on the medium while changing a relative position between the element and the medium, and a transport operation for transporting the medium.
(G) The controller changes a drive signal generation unit that generates the first drive signal from the first drive signal generation unit to the second drive signal generation unit during the dot formation operation. Printing device.
According to such a printing apparatus, it is possible to suppress deterioration in the image quality of the printed image even if the characteristics of the respective drive signal generation units vary.

  In addition, when forming the dot of the predetermined size at the certain timing, the controller generates the first drive signal by the first drive signal generation unit and performs the second drive by the second drive signal generation unit. When the signal is generated and the dot of the predetermined size is formed at the different timing, the controller causes the second drive signal generator to generate the first drive signal and the first drive signal generator Preferably, the second drive signal is generated. Thereby, since the drive signal generated by the first drive signal generation unit and the drive signal generated by the second drive signal generation unit can be interchanged, even if the characteristics of the respective drive signal generation units vary, It is possible to suppress a decrease in the image quality of the printed image.

  The printing apparatus may further include another drive signal generation unit different from the first drive signal generation unit and the second drive signal generation unit, and when forming the dot of the predetermined size at the certain timing, The controller causes the first drive signal generation unit to generate the first drive signal, the second drive signal generation unit to generate a second drive signal, and forms dots of the predetermined size at the different timing. In this case, it is preferable that the controller causes the second drive signal generation unit to generate the first drive signal and causes the other drive signal generation unit to generate the second drive signal. As a result, it is possible to suppress a reduction in the image quality of the print image without replacing the drive signal generated by the first drive signal generation unit and the drive signal generated by the second drive signal generation unit.

  In addition, it is preferable that the controller changes a drive signal generation unit that generates the first drive signal for each period in which dots for one pixel are formed. Thereby, degradation of image quality can be further suppressed.

The printing apparatus includes a moving body that moves the element in a moving direction to change a relative position between the element and the medium, and a sensor that detects a position of the moving body,
The controller may change a drive signal generation unit that generates the first drive signal according to a detection result of the sensor. Thereby, the controller can acquire the timing which should replace a drive signal.

  The controller may change the order of the drive signals generated by the first drive signal generation unit and the second drive signal generation unit for each dot formation operation. As a result, the image quality of the printed image becomes uniform and the image quality is improved.

The printing apparatus can form dots of a plurality of sizes,
It is preferable that the controller selectively applies a drive pulse included in the first drive signal or the second drive signal to the element according to the size of the dot to be formed. In addition, when two or more drive pulses are applied to the element when forming the dot of the predetermined size, one of the first drive signal generation unit and the second drive signal generation unit is the predetermined size. When generating the drive pulse for forming the other dots, it is preferable that the other generates the drive pulse for forming dots of other sizes. As a result, the printing resolution is improved and the printing speed is improved. The controller applies a drive pulse included in the drive signal generated by the first drive signal generation unit to the element when forming the largest size dot, and generates the second drive signal generation unit. It is desirable to apply a driving pulse included in the driving signal to the element. Thereby, the bias | inclination of the emitted-heat amount can be reduced.

An element driven to form a dot, a first drive signal generator for generating a drive signal for driving the element, and a second drive signal generator for generating a drive signal for driving the element And preparing a printing apparatus having
When forming dots of a predetermined size at a certain timing, the first drive signal generation unit generates a first drive signal,
A printing method for generating the first drive signal by the second drive signal generation unit when forming the dot of the predetermined size at another timing,
A dot forming operation for forming dots on the medium while changing a relative position between the element and the medium and a transport operation for transporting the medium are alternately repeated.
A printing method, wherein a drive signal generation unit that generates the first drive signal is changed from the first drive signal generation unit to the second drive signal generation unit during the dot forming operation.
According to such a printing method, it is possible to suppress a decrease in the image quality of the printed image even if the characteristics of the respective drive signal generation units vary.

An element driven to form a dot, a first drive signal generator for generating a drive signal for driving the element, and a second drive signal generator for generating a drive signal for driving the element And a printing apparatus having
When forming dots of a predetermined size at a certain timing, the first drive signal generator generates a first drive signal,
When forming the dot of the predetermined size at another timing, the second drive signal generation unit generates the first drive signal,
A dot forming operation for forming dots on the medium while changing the relative position between the element and the medium, and a transport operation for transporting the medium are alternately repeated,
A program that changes a drive signal generation unit that generates the first drive signal from the first drive signal generation unit to the second drive signal generation unit during the dot forming operation.
According to such a program, even if there are variations in the characteristics of the respective drive signal generation units, it is possible to cause the printing apparatus to print so as to suppress a decrease in image quality of the print image.

A printing system comprising a computer and a printing device,
The printing apparatus includes:
(A) an element driven to form a dot;
(B) a first drive signal generation unit that generates a drive signal for driving the element;
(C) a second drive signal generation unit that generates a drive signal for driving the element;
(D) When forming dots of a predetermined size at a certain timing, the first drive signal generator generates a first drive signal;
A controller that generates the first drive signal in the second drive signal generation unit when forming the dot of the predetermined size at another timing;
Have
The printing apparatus repeats alternately a dot forming operation for forming dots on the medium while changing a relative position between the element and the medium, and a transport operation for transporting the medium,
The controller changes a drive signal generation unit that generates the first drive signal from the first drive signal generation unit to the second drive signal generation unit during the dot formation operation.
According to such a printing system, it is possible to suppress deterioration in the image quality of the printed image even if the characteristics of the respective drive signal generation units vary.

=== Printing system ===
First, the printing apparatus will be described together with a printing system. The printing system is a system including at least a printing apparatus and a printing control apparatus that controls the operation of the printing apparatus.

  FIG. 1 is a diagram illustrating the configuration of the printing system 100. The illustrated printing system 100 includes a printer 1 as a printing apparatus and a computer 110 as a printing control apparatus. Specifically, 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 of Computer 110>
FIG. 2A is a block diagram illustrating configurations of the computer 110 and the printer 1. FIG. 2B is a diagram schematically illustrating a part of the memory 63 included in 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 for securing 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 printer driver causes the computer 110 to realize a function of converting image data output from the application program into print data. The printer 1 receives the print data from the computer 110 and executes a printing operation. In other words, it can be said that the computer 110 controls the operation of the printer 1 via the print data. Therefore, the computer 110 functions as a print control apparatus by using this printer driver. The printer driver has a code for realizing a function of converting image data into print data.

  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). In the present embodiment, the pixel data is composed of 2-bit data. That is, the pixel data corresponds to pixel data “00” corresponding to no dot, pixel data “01” corresponding to small dots, pixel data “10” corresponding to formation of medium dots, and large dots. Pixel data “11”. Therefore, the printer 1 can express four gradations in one pixel.

  The printer driver performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, and the like in order to convert image data output from the application program into print data. The printer driver is provided in a state where it is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. The printer driver can also be downloaded to the computer 110 via the Internet.

=== Printer ===
<About the configuration of the printer 1>
Next, the configuration of the printer 1 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. 2A is also referred to.

  As illustrated in FIG. 2A, the printer 1 includes a paper transport mechanism 20, a carriage movement 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 corresponds to a medium transport unit that transports a medium. 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 side to the other side and a movement direction from the other side to the one side. Since the head unit 40 includes the head 41, the carriage movement direction corresponds to the movement direction of the head 41, and the carriage movement mechanism 30 corresponds to a head moving unit that moves the head 41 in the movement direction. 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 40>
The head unit 40 is for ejecting ink toward the paper S. The head unit 40 includes a head controller HC and a head 41. The configuration of the head controller HC will be described in detail later. The head 41 is provided with a plurality of ink columns corresponding to the respective ink colors. Each ink row is provided with a plurality of nozzles, and each nozzle is provided with a piezo element. When this piezo element is driven, a pressure chamber (not shown) is deformed, and an ink droplet is ejected from the nozzle by the pressure generated thereby, and a dot is formed when the ink droplet lands on the paper.

  In the printer 1, as described above, there is no dot corresponding to the pixel data “00”, a small dot corresponding to the pixel data “01”, a medium dot corresponding to the pixel data “10”, and the pixel data “11”. ”Can be controlled to express four types of gradations of large dots. For this reason, a plurality of types of ink having different amounts can be ejected from each nozzle. For example, from each nozzle, there are three types of ink consisting of large ink droplets capable of forming large dots, medium ink droplets capable of forming medium dots, and small ink droplets capable of forming small dots. Can be discharged.

<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. 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. Although not shown, a temperature detector that detects the temperature around the head 41 is also provided.

<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. Therefore, the printer-side controller 60 and the head controller HC are controllers that cause the drive signal generation circuit 70 to generate action signals including drive pulses, and correspond to a controller that applies the generated drive pulses to the piezo element 417.

  As shown in FIG. 2A, 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, as shown in FIG. 2B, a part of the memory 63 is used as a program storage area 63a, a waveform storage area 63b, and an adjustment value storage area 63c. The program storage area 63a is an area for storing computer programs. The waveform storage area 63b is an area in which waveform data for generating a drive signal is stored. The adjustment value storage area 63c is an area in which adjustment values for adjusting variations between the first waveform generation circuit 71A and the second waveform generation circuit 71B (see FIG. 4) of the drive signal generation circuit 70 are stored. .

  And CPU62 controls each control object part according to the computer program memorize | stored in the program storage area 63a of the memory 63. FIG. 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.

=== 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. 4 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. 5A 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. FIG. 5B is a diagram for explaining the relationship between the DAC value input to the D / A converter 711A and the output voltage from the voltage amplification circuit 712A.

  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 63b. In the present embodiment, the DAC value is composed of 10-bit data, but for the sake of convenience, it is represented in hexadecimal in the figure.

  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.

For example, in the example shown in FIG. 5B, when the DAC value input from the CPU 62 to the D / A converter 711A is “24Eh” in hexadecimal (in the case of “1001001110” in binary), the DAC is amplified by the voltage amplification circuit 712A. After that, the output voltage becomes 25V. When the DAC value input from the CPU 62 to the D / A converter 711A is “0h” in hexadecimal (in the case of “0000000” in binary), the output voltage after being amplified by the voltage amplification circuit 712A is 1 When the input DAC value is “3FF” in hexadecimal (in the case of “1111111111” in binary), the output voltage after being amplified by the voltage amplification circuit 712A is 42.32V. That is, the minimum output voltage of the first drive signal generation unit 70A is 1.4V, and when the DAC value input from the CPU 62 increases by one, the output voltage of the first waveform generation circuit increases by 0.04V.
However, due to manufacturing variations, an ideal output as shown in FIG. 5B is not always obtained. A method for suppressing the influence of this manufacturing variation will be described later.

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

  The CPU 62 of the printer-side controller 60 first obtains an output voltage for each update cycle τ based on a parameter for generating the drive signal COM. Taking the drive pulse PS ′ shown in FIG. 6A as an example, parameters include a drive voltage Vh, a ratio that defines the relationship between the drive voltage Vh and the reference voltage Vc, a time PWh1 for maintaining the intermediate voltage VC, A time PWd1 for dropping the voltage from the intermediate voltage VC to the lowest voltage VL with a constant slope; a time PWh2 for maintaining the lowest voltage VL; a time PWc1 for raising the voltage with a constant slope from the lowest voltage VL to the highest voltage VH; There is a time PWh3 for maintaining the maximum voltage VH, a time PWd2 for dropping the voltage with a constant gradient from the maximum voltage VH to the intermediate voltage VC, and a time PWh4 for maintaining the intermediate voltage VC.

  Here, the drive voltage Vh is a voltage difference between the highest voltage VH and the lowest voltage VL in the drive pulse PS ′. In other words, this corresponds to the difference between the lowest potential (potential determined by the lowest voltage VL) and the highest potential (potential determined by the highest voltage VH) in the piezo element 417. The reference voltage Vc defines a deformation state that serves as a reference for the piezo element 417. In the present embodiment, the reference voltage Vc is 40% of the drive voltage Vh. For this reason, the value “0.4” is stored as a ratio that defines the relationship between the drive voltage Vh and the reference voltage Vc. The intermediate voltage VC is a voltage obtained by adding the reference voltage Vc to the minimum voltage VL. The maximum voltage VH is a voltage obtained by adding the drive voltage Vh to the minimum voltage VL. Parameters other than the drive voltage Vh are stored in the waveform storage area 63 b of the memory 63. Regarding the drive voltage Vh, a reference voltage value (also referred to as a reference drive voltage Vhs for convenience) is stored in the waveform storage area 63b. That is, the drive voltage Vh that is actually used is determined by correcting the reference drive voltage Vhs based on the ambient temperature of the head 41 and the like.

  The CPU 62 acquires the ambient temperature of the head 41 at a predetermined timing (for example, paper feed timing), and determines the drive voltage Vh based on the acquired ambient temperature. When the drive voltage Vh is determined, the CPU 62 calculates a reference voltage Vc, an intermediate voltage VC, and a maximum voltage VH. And CPU62 calculates | requires the output voltage for every update period (tau) using time PWh1-time PWh4 mentioned above. The update period τ is, for example, 0.1 μs (clock CLK = 10 MHz) to 0.05 μs (clock CLK = 20 MHz). Then, based on the obtained output voltage for each update cycle τ, a DAC value for each update cycle τ is determined and stored, for example, in a work area (not shown) of the memory 63.

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. 6B, 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.
In this way, the drive signal shown in FIG. 6A is output from the first waveform generation circuit 71A.

<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 generation unit 70A and the second drive signal generation unit 70B generate different drive signals COM, respectively. 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. However, in the present embodiment, as described later, the first drive signal generation unit 70A and the second drive signal generation unit 70B alternately generate the first drive signal COM_A and the second drive signal COM_B.

FIG. 9 shows the first drive signal COM_A and the second drive signal COM_B.
The first drive signal COM_A includes a first waveform section SS11a generated in the period T1 in the repetition period T, a second waveform section SS12a generated in the period T2, and a third waveform section SS13a generated in the period T3. Have. Each of these waveform portions has a drive pulse. That is, the first waveform section SS11a has the drive pulse PS1. The second waveform section SS12a has a drive pulse PS2, and the third waveform section SS13a has a drive pulse PS3.

  The drive pulse PS1 and the drive pulse PS3 of the first drive signal COM_A are applied to the piezo element 417 when a large dot is formed, and have the same waveform. The drive pulse PS2 is applied to the piezo element 417 when a small dot is formed. The drive pulse PS2 has a waveform different from that of the drive pulse PS1 and the drive pulse PS3. That is, when the drive pulse PS2 is applied to the piezo element 417, the sequence for deforming the piezo element 417 is different from the sequence when the drive pulse PS1 is applied to the piezo element 417. Therefore, by applying the drive pulse PS2 to the piezo element 417, an amount of ink droplets different from that when the drive pulse PS1 is applied is ejected from the nozzle. That is, by applying this drive pulse PS2 to the piezo element 417, a small ink droplet is ejected from the head 41.

  The second drive signal COM_B includes a first waveform section SS21a generated in the period T1, a second waveform section SS22a generated in the period T2, and a third waveform section SS23a generated in the period T3. In the present embodiment, the first waveform portion SS21a to the third waveform portion SS23a of the second drive signal COM_B are set to the same time width as the first waveform portion SS11a to the third waveform portion SS13a of the corresponding first drive signal COM_A. ing. Accordingly, the first change signal CH_A for the first drive signal COM_A and the second change signal CH_B for the second drive signal COM_B are aligned at the H level. In the second drive signal COM_B, the first waveform section SS21a has a drive pulse PS4, and the second waveform section SS22a has a drive pulse PS5.

  The drive pulse PS4 of the second drive signal COM_B is applied to the piezo element 417 when the medium dot is formed. The drive pulse PS4 has a waveform different from that of the drive pulse PS1 and the drive pulse PS2. Thus, when the drive pulse PS4 is applied to the piezo element 417, the sequence for deforming the piezo element 417 is different from the sequence corresponding to the drive pulse PS1 and the sequence corresponding to the drive pulse PS2. For this reason, by applying the drive pulse PS4 to the piezo element 417, it is possible to eject an amount of ink different from that when the drive pulse PS1 or the drive pulse PS2 is applied. That is, by applying the drive pulse PS4 to the piezo element 417, the medium ink droplet is ejected from the head 41. Accordingly, the drive pulse PS4 defines the start to end of the operation for ejecting ink when forming the medium dot.

  The drive pulse PS5 is applied to the piezo element 417 when a large dot is formed. The drive pulse PS5 has the same waveform as the drive pulse PS1 and the drive pulse PS3. Accordingly, the drive pulse PS1, the drive pulse PS3, and the drive pulse PS5 applied to the piezo element 417 at the time of forming a large dot all have the same waveform. In the second drive signal, the third waveform section SS23a generated in the period T3 is a constant voltage signal that is constant at the intermediate voltage VC.

<About the head controller HC>
FIG. 8 is a block diagram illustrating the configuration of the head controller HC. As shown in the figure, 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, 1 switch 87A and 2nd 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 switch 87A, and the second switch The switch 87B is provided for each piezo element 417. In addition, since the piezo element 417 is provided for each nozzle, in other words, each of these parts is provided for each nozzle.

  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. Each nozzle row of the head 41 of the present embodiment has 180 nozzles from the first nozzle # 1 to the 180th nozzle # 180. Therefore, the pixel data includes the upper bits of nozzle # 1, the upper bits of nozzle # 2,..., The upper bits of nozzle # 179, the upper bits of nozzle # 180, the lower bits of nozzle # 1, and the lower bits of nozzle # 2. ,... Are sent in the order of the lower bits of nozzle # 179 and the lower bits of nozzle # 180. As a result, the upper bit group of each pixel data is set in the first shift register 81A, and the lower bit group is set in the second shift register 81B.

A first latch circuit 82A is electrically connected to each first shift register 81A, and a second latch circuit 82B is electrically connected to each second shift register 81B. When the latch signal LAT from the printer-side controller 60 becomes H level, that is, when a latch pulse is input to the first latch circuit 82A and the second latch circuit 82B, the first latch circuit 82A is in the first shift register 81A. The second latch circuit 82B latches the lower bits of the second shift register 81B.
A decoder 83 is electrically connected to the first latch circuit 82A and the second latch circuit 82B. Pixel data (a set of upper bits and lower bits) latched in the first latch circuit 82A and the second latch circuit 82B is input to the decoder 83, respectively.

FIG. 9 shows the latch signal LAT, the first change signal CH_A, and the second change signal CH_B. Further, in this figure, waveform selection signals q0 to q7 are shown.
A latch signal LAT, a first change signal CH_A, and a second change signal CH_B are input from the CPU 62 to the control logic 84. The control logic 84 generates the waveform selection signals q0 to q3 shown in FIG. 9 based on the latch signal LAT and the first change signal CH_A. Further, the control logic 84 generates the waveform selection signals q4 to q7 shown in FIG. 9 based on the latch signal LAT and the second change signal CH_B. The waveform selection signals q0 to q7 generated by the control logic 84 are input to each decoder 83.

  The decoder 83 controls the first switch control signal SW1 for controlling on / off of the first switch 87A and the on / off of the second switch 87B based on the pixel data latched by the first latch circuit 82A and the second latch circuit 82B. The second switch control signal SW2 is output. When the pixel data is “00”, the decoder 83 outputs the waveform selection signal q0 as the first switch control signal SW1, and outputs the waveform selection signal q4 as the second switch control signal SW2. When the pixel data is “01”, the decoder 83 outputs the waveform selection signal q1 as the first switch control signal SW1, and outputs the waveform selection signal q5 as the second switch control signal SW2. When the pixel data is “10”, the decoder 83 outputs the waveform selection signal q2 as the first switch control signal SW1, and outputs the waveform selection signal q6 as the second switch control signal SW2. When the pixel data is “11”, the decoder 83 outputs the waveform selection signal q3 as the first switch control signal SW1, and outputs the waveform selection signal q7 as the second switch control signal SW2. If the first switch control signal SW1 is at H level, the first switch 87A is turned on, and if it is at L level, it is turned off. Similarly, the second switch 87B is turned on when the second switch control signal SW2 is at the H level, and is turned off when it is at the L level.

  The first drive signal COM_A is commonly input to the first switches 87A, and the second drive signal COM_B is commonly input to the second switches 87B. If the first switch 87A is on, the first drive signal COM_A is input to the piezo element 417. If the first switch 87A is in the OFF state, the first drive signal COM_A is not input to the piezo element 417. The same applies to the second switch 87B. The output side of the first switch 87A and the output side of the second switch 87B are both electrically connected to the piezo element 417. When the first switch 87A is turned on / off, the waveform portions SS11a to SS13a constituting the first drive signal COM_A are selectively applied to the piezo element 417. Further, when the second switch 87B is turned on / off, the waveform portions SS21a to SS23a constituting the second drive signal COM_B are selectively applied to the piezo element 417.

  Note that, for any pixel data, the waveform selection signals q0 to q7 are set in advance so that the first switch control signal SW1 and the second switch control signal SW2 do not simultaneously become the H level. This prevents the first drive signal COM_A and the second drive signal COM_B from being applied to the piezo element 417 at the same time.

<Signal applied to piezo element 417>
FIG. 10 is an explanatory diagram of signals applied to the piezo element 417. The head controller HC applies a signal corresponding to the pixel data to the piezo element 417 as described below.

  When the pixel data is “00”, the first switch control signal SW1 and the second switch control signal SW2 are both at the L level over the periods T1 to T3. For this reason, since the first switch 87A and the second switch 87B remain in the OFF state, no drive pulse is applied to the piezo element 417. For this reason, no ink is ejected from the nozzles, and no dots are formed.

  When the pixel data is “01”, the first switch control signal SW1 becomes H level in the period T2, so that the drive pulse PS2 of the second waveform portion SS12a of the first drive signal COM_A is applied to the piezo element 417. As a result, an amount of ink corresponding to the small dots is ejected from the nozzles.

  When the pixel data is “10”, the second switch control signal SW1 becomes H level in the period T1, and thus the drive pulse PS4 of the first waveform portion SS21a of the second drive signal COM_B is applied to the piezo element 417. As a result, an amount of ink corresponding to the medium dot is ejected from the nozzle.

  When the pixel data is “11”, the first switch control signal SW1 becomes H level in the period T1, the second switch control signal SW2 becomes H level in the period T2, and the first switch control signal SW1 becomes H in the period T3. Become a level. Therefore, the drive pulse PS1 of the first waveform portion SS11a of the first drive signal COM_A is applied to the piezo element 417 in the period T1, and the drive pulse PS5 of the second waveform section SS22a of the second drive signal COM_B is the piezo element in the period T2. The drive pulse PS6 of the third waveform portion SS13a of the first drive signal COM_A is applied to the piezo element 417 in the period T3. As a result, an amount of ink corresponding to a large dot is ejected from the nozzle.

=== 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. Therefore, this computer program has a code for executing this control. Then, the printing operation on the paper S is performed by controlling the control target portion.

  Here, FIG. 11 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.

=== Operation of Reference Example ===
<Necessity of replacement of drive signal>
The first current amplifier circuit 72A consumes power as the drive signal COM is generated. That is, the first current amplifier circuit 72A consumes power due to the collector loss of the NPN transistor Q1 and the collector loss of the PNP transistor Q2 when the drive signal COM is generated. Since the second current amplifier circuit 72B is the same, only the first current amplifier circuit 72A will be described here.

  FIG. 12 is an explanatory diagram of the relationship between the drive pulse PS1 and power consumption. Here, the power consumption of the transistor pair 721A when the drive pulse PS1 is applied to the piezo element 417 will be described.

  The NPN transistor Q1 of the first current amplifier circuit 72A is turned on when the voltage of the drive signal COM is increased, that is, when the piezo element 417 is charged. On the other hand, the PNP transistor Q2 is turned on when the voltage of the drive signal COM is dropped, that is, when the piezo element 417 is discharged.

  For this reason, during the period from time t21 to time t22 in the figure, the voltage of the drive signal COM is decreasing, so that the PNP transistor Q2 consumes power. Further, in the period from time 23 to time t24 in the figure, the voltage of the drive signal COM is rising, so that the NPN transistor Q1 consumes power. Further, during the period from time t25 to time t26 in the figure, the voltage of the drive signal COM rises, so that the PNP transistor Q2 consumes power.

  The power consumption of the NPN transistor Q1 is the product of the difference between the power supply potential PWmax and the potential of the drive signal COM and the current I1 (see FIG. 7A) flowing through the NPN transistor Q1. On the other hand, the power consumption of the PNP transistor Q2 is the product of the difference between the potential of the drive signal COM and the ground potential GND and the current I2 flowing through the PNP transistor Q2 (see FIG. 7A). Therefore, the power consumption of the transistor pair 721A when the drive pulse PS1 is applied to the piezo element 417 is based on the potential difference in the periods indicated by hatching in the drawing and the currents I1 and I2 flowing in these periods. Is calculated. In the reference example, when the driving pulse PS1 is applied to all 180 piezo elements 417 corresponding to one nozzle row, 1.5 W of power is consumed by the transistor pair 721A.

  FIG. 13 is an explanatory diagram of a relationship between the first drive signal COM_A and the second drive signal COM_B and power consumption. Since the drive pulse applied to the piezo element 417 varies depending on the dot size (see FIG. 10), the power consumption varies depending on the dot size. Further, since the applied drive pulse is included in either the first drive signal COM_A or the second drive signal COM_B, the transistor pair 721A that generates the first drive signal COM_A and the transistor that generates the second drive signal COM_B The power consumption is different from the pair 721B.

  For example, when forming a small dot, only the drive pulse PS2 of the first drive signal COM_A is applied to the piezo element 417. Therefore, when forming a small dot, 3.0 W of power is consumed only by the transistor pair 721A that generates the first drive signal COM_A, and no power is consumed by the transistor pair 721B that generates the second drive signal COM_B.

When forming a medium dot, since only the drive pulse PS4 of the second drive signal COM_B is applied to the piezo element 417, no power is consumed in the transistor pair 721A that generates the first drive signal COM_A, and the second drive signal COM_B. The power of 2.0 W is consumed in the transistor pair 721B that generates Note that the amount of power consumption differs between the case of forming a small dot and the case of forming a medium dot. The drive pulse PS2 for forming a small dot and the drive pulse PS4 for forming a medium dot are different. This is because the waveforms are different.
When forming a large dot, the drive pulse PS1 of the first drive signal COM_A, the drive pulse PS5 of the second drive signal COM_B, and the drive pulse PS3 of the first drive signal COM_A are applied to the piezo element 417. Therefore, when forming a large dot, 3.0 W of power is consumed by the transistor pair 721A that generates the first drive signal COM_A, and 1.5 W of power is consumed by the transistor pair 721B that generates the second drive signal COM_B. Is done.

  In this way, regardless of which dot is formed, the power consumption of the transistor pair 721A that generates the first drive signal COM_A is different from the power consumption of the transistor pair 721B that generates the second drive signal COM_B. become.

  By the way, the fact that the power consumption is different means that the heat generation amount is different. Therefore, when the first drive signal generation unit 70A continues to generate the first drive signal COM_A and the second drive signal generation unit 70B continues to generate the second drive signal COM_B, one transistor pair becomes the other transistor pair. On the other hand, it generates heat unevenly. For example, when large dots continue to be formed, the transistor pair 721A of the first drive signal generation unit 70A generates more heat than the transistor pair 721B of the second drive signal generation unit 70B.

  When one transistor pair generates heat in a biased manner in this way, it is necessary to design the heat sink 722 in accordance with the transistor pair that generates a large amount of heat. In this case, an excessive heat sink 722 is provided for a pair of transistors that generate a small amount of heat, resulting in an increase in the size of the device.

  Therefore, in the reference example, the drive signals COM generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B are alternately replaced. Thus, the transistor pair 721A of the first drive signal generation unit 70A and the transistor pair 721B of the second drive signal generation unit 70B generate heat equally.

<Processing when the drive signal is switched 1>
The case where the first drive signal generation unit 70A has already generated the first drive signal COM_A and the second drive signal generation unit 70B has already generated the second drive signal COM_B has been described. Therefore, the case where the generated drive signals are replaced, the first drive signal generation unit 70A generates the second drive signal COM_B, and the second drive signal generation unit 70B generates the first drive signal COM_A will be described below.

  The CPU 62 sequentially outputs a DAC value for generating the second drive signal COM_B to the D / A converter 711A of the first waveform generation circuit 71A of the first drive signal generation unit 70A. Accordingly, the second drive signal COM_B is output from the first drive signal generation unit 70A. Similarly, the CPU 62 sequentially outputs a DAC value for generating the first drive signal COM_A to the D / A converter 711B of the second waveform generation circuit 71B of the second drive signal generation unit 70B. Accordingly, the first drive signal COM_A is output from the second drive signal generation unit 70B.

As a result, the first drive signal COM_A and the second drive signal COM_B in FIG. 8 are interchanged. That is, the first drive signal COM_A is input to the second switch 87B, and the second drive signal COM_B is input to the first switch 87A. For this reason, the switch control signal SW1 and the switch control signal SW2 also need to be interchanged. (If the switch signal is not replaced, for example, in the case of pixel data “01” (small dot), the drive pulse PS5 of the second drive signal COM_B is applied instead of the drive pulse PS2 of the first drive signal COM_A. The amount of ink that does not correspond to the small dots is ejected.)
Therefore, the waveform selection signals q0 to q7 output from the control logic 84 are also changed with the replacement of the drive signal COM. Specifically, when the first drive signal generation unit 70A generates the first drive signal COM_A, the control logic 84 outputs the waveform selection signal q4 to the signal line that has output the waveform selection signal q0. The waveform selection signal q5 is output to the signal line that has output the waveform selection signal q1, the waveform selection signal q6 is output to the signal line that has output the waveform selection signal q2, and the waveform selection signal q3 is output. The waveform selection signal q7 is output to the signal line. As described above, the waveform selection signals q0 to q3 and the waveform selection signals q4 to q7 output from the control logic 84 are exchanged with the exchange of the drive signal COM.

  Through the above processing, the drive signals COM generated by the first drive signal generator 70A and the second drive signal generator 70B can be interchanged. In addition, according to the above processing, dots corresponding to the pixel data can be formed even when the drive signal COM is replaced.

<Processing 2 when driving signals are replaced>
FIG. 14 is a diagram illustrating another example of processing when switching drive signals. The upper two diagrams show a state where 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. In the two lower diagrams, the driving signals to be generated are interchanged, and the first driving signal generation unit 70A generates the second driving signal COM_B, and the second driving signal generation unit 70B generates the first driving signal COM_A. Is shown.

  In this example, the output destinations of the two D / A converters are switched. As a result, the drive signals COM generated by the first drive signal generator 70A and the second drive signal generator 70B can be interchanged. In this example, the output destinations of the first switch control signal SW1 and the second switch control signal SW2 output from the decoder 83 are switched. Thereby, even when the drive signal COM is replaced, dots corresponding to the pixel data can be formed.

  In this example, the DAC value input to the D / A converter 711A and D / A converter 711B by the CPU 62 does not change before and after the replacement (in the above example, the CPU 62 performs the D / A conversion). The DAC values input to the converter 711A and the D / A converter 711B have been switched). In this example, the waveform selection signals q0 to q7 input to the decoder 83 by the control logic 84 are not changed before and after the replacement (in the above example, the waveform selection signals q0 to q3 and the waveform selection signal q4 are not changed). It was replaced with ~ q7). For this reason, according to this example, the processing of the CPU 62 can be simplified, and the configuration of the control logic 84 can also be simplified.

<About the replacement timing of the reference example>
Next, drive signal replacement timing will be described.
For example, the printer can exchange the first drive signal COM_A and the second drive signal COM_B every time one sheet of paper is printed. As a result, the drive signals can be exchanged at a regular timing.
However, in some cases, a text image mainly composed of large dots is printed on odd pages, and an image mainly composed of medium dots is printed on even pages, and a plurality of sheets are continuously printed. In such a case, the heat generation is biased to the transistor pair of the drive signal generation unit that generates the first drive signal COM_A when the large dot is formed, and the transistor pair of the drive signal generation unit that generates the second drive signal COM_B when the medium dot is formed. Since the heat generation is biased (see FIG. 13), if the drive signal is replaced every time one sheet is printed, the heat generation may be biased to the transistor pair of one drive signal generation unit.

  In order to avoid such a situation, it is desirable to replace the drive signal during printing on one sheet. Therefore, for example, the printer can change the drive signal every time the dot forming operation (S30, see FIG. 11) is performed several times. Thus, even when different types of images are continuously printed for each page, the transistor pair 721A of the first drive signal generation unit 70A and the transistor pair 721B of the second drive signal generation unit 70B generate heat equally.

  However, in one sheet of paper, a text image mainly composed of large dots may be printed at the top of the sheet, and an image mainly composed of medium dots may be printed at the bottom of the sheet. In such a case, if the timing at which the drive signal is switched every several dot forming operations (S30) is between printing on the upper part of the paper and printing on the lower part of the paper, heat is generated in the transistor pair of one drive signal generation unit. May be biased.

  Therefore, in the reference example, the drive signal is replaced for each dot forming operation (S30). Even when a plurality of different types of images are printed on one sheet, individual images are often printed by a plurality of dot forming operations. For this reason, if the drive signals are exchanged for each dot forming operation (S30), the transistor pair 721A of the first drive signal generation unit 70A and the transistor pair 721B of the second drive signal generation unit 70B will generate heat equally.

=== Variation in characteristics of two drive signal generation units ===
By the way, the first drive signal generator 70A and the second drive signal generator 70B described above have the same configuration, but due to the influence of manufacturing variation, the first drive signal generator 70A and the second drive signal generator 70B. The characteristics may vary.
FIG. 15A is a diagram illustrating the drive pulse PS2 generated by the first drive signal generation unit 70A. FIG. 15B is a diagram illustrating a relationship between the DAC value input to the first drive signal generation unit 70A and the output voltage. FIG. 15C is a diagram illustrating the drive pulse PS2 generated by the second drive signal generation unit 70B. FIG. 15D is a diagram illustrating a relationship between the DAC value input to the second drive signal generation unit 70B and the output voltage.

  In the following description, the DAC value output from the CPU 62 for setting the maximum voltage VH is referred to as “DAC_VH” (that is, the DAC value output from the CPU 62 at the maximum voltage VH is “DAC_VH”). The DAC value output from the CPU 62 to set the minimum voltage VL is referred to as “DAC_VL”. The DAC value output from the CPU 62 to obtain the intermediate voltage VC is referred to as “DAC_VC”.

  In this example, the second drive signal generation unit 70B has a characteristic of outputting a higher voltage than the first drive signal generation unit 70A. That is, in the first drive signal generation unit 70A, when the DAC value “00Fh” is input, a voltage of 2.00 V is output, and when the DAC value “280h” is input, a voltage of 27.00 V is output. The second drive signal generator 70B outputs a voltage of 2.04V when the DAC value “00Fh” is input, and outputs a voltage of 27.36V when the DAC value “280h” is input.

Here, in the drive pulse PS2, the voltage when the DAC value “00Fh” is input corresponds to the lowest voltage VL, and the voltage when the DAC value “280h” is input corresponds to the highest voltage VH. For this reason, the drive voltage Vh_PS21 of the drive pulse PS2 when the first drive signal generator 70A generates the first drive signal COM_A is 25.00V. On the other hand, the drive voltage Vh_PS22 of the drive pulse PS2 when the second drive signal generation unit 70B generates the first drive signal COM_A is 25.36V.
When the driving voltage is different, the amount of expansion and contraction of the piezo element is different, so that the pressure fluctuation for the ink in the pressure chamber is different. As a result, when the driving voltage is different, the amount of ejected ink is different. That is, the small dots formed when the first drive signal generation unit 70A generates the first drive signal COM_A and the second dots generated when the second drive signal generation unit 70B generates the first drive signal COM_A. Since the amount of ejected ink is different from the small dots, the dot diameter is different.

  If the drive signal is exchanged for each dot forming operation as in the above-described reference example, the dot diameter is small between a small dot formed in one dot forming operation and a small dot formed in the next dot forming operation. Will be different. Normally, in each dot forming operation, ink droplets are intermittently ejected from each nozzle to form a row of dots (called a dot row or raster line). Different raster lines are formed. In a printed image composed of such raster lines, a light and dark stripe pattern is generated due to the difference in the thickness of the raster lines, resulting in poor image quality.

  Therefore, in the present embodiment described below, the drive signals generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B are interchanged during the dot formation operation for forming the raster line. As a result, each raster line is formed so that dots of different sizes are mixed, the thickness of each raster line is uniform, and even if the characteristics of the two drive signal generators vary, the degradation in image quality is suppressed can do.

=== Operation of this Embodiment ===
<Operation of drive signal generator>
FIG. 16 is an explanatory diagram of drive signals generated by each drive signal generation unit of the present embodiment. In the drawing, a detection signal PTS and a latch signal LAT are shown for explaining the timing of the drive signal.

  The detection signal PTS is a detection signal output from the linear encoder 51. The linear encoder 51 outputs a pulse PTS_P every time the carriage CR moves 1/360 inch in the movement direction. For this reason, if the pulse PTS_P of the detection signal PTS is output, it means that the carriage CR has moved by 1/360 inch after the immediately preceding pulse PTS_P was output. This detection signal PTS is output from the linear encoder 51 to the printer-side controller 60.

  The printer-side controller 60 measures the pulse period of the detection signal PTS from the linear encoder 51 and calculates a half time of this pulse period. The printer-side controller 60 outputs a pulse LAT_P as a LAT signal simultaneously with the pulse PTS_P of the detection signal PTS, and the pulse LAT_P even when half the time of the pulse period of the detection signal PTS has elapsed since the output of the pulse LAT_P. Is output. For example, the printer-side controller outputs a pulse LAT_P3 of the latch signal LAT based on the pulse PTS_P2 of the detection signal PTS in the figure, and calculates a time that is half the pulse period of the pulses PTS_P1 and PTS_P2 of the detection signal PTS. The pulse LAT_P4 is output after the pulse LAT_P3 of the latch signal LAT.

  In the latch signal LAT generated in this way, if the pulse LAT_P is output, it means that the carriage CR has moved by about 1/720 inch after the immediately preceding pulse LAT_P was output. When the printer performs printing at a resolution of 720 dpi, the latch signal LAT is a signal indicating that the carriage CR has moved through a section corresponding to one pixel. Then, ink for one pixel is ejected between the pulses of the latch signal LAT. That is, the above-described repetition period T is a period in which ink for one pixel is ejected. In the figure, drive signals for four pixels are shown, and the period T corresponding to the nth pixel is denoted as T (n).

  In the period T corresponding to the odd-numbered pixels, 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. For example, in the figure, in the cycle T (1) corresponding to the first pixel and the cycle T (3) corresponding to the third pixel, the first drive signal generator 70A generates the first drive signal COM_A, The second drive signal generation unit 70B generates a second drive signal COM_B. Hereinafter, a period corresponding to an odd-numbered pixel (for example, period T (1) or period T (3)) is referred to as an “odd pixel period”.

  In the period T corresponding to the even-numbered pixels, the first drive signal generation unit 70A generates the second drive signal COM_B, and the second drive signal generation unit 70B generates the second drive signal COM_B. For example, in the drawing, in the cycle T (2) corresponding to the second pixel and the cycle T (4) corresponding to the fourth pixel, the first drive signal generation unit 70A generates the second drive signal COM_B, The second drive signal generation unit 70B generates a second drive signal COM_B. Hereinafter, a cycle corresponding to even-numbered pixels (for example, cycle T (2) or cycle T (4)) is referred to as an “even pixel cycle”.

  Each time the detection signal PTS is input to the printer-side controller 60, the first drive signal generation unit 70A repeatedly generates drive signals for two cycles in the order of the first drive signal COM_A and the second drive signal COM_B. Yes. Each time the detection signal PTS is input to the printer-side controller 60, the second drive signal generator 70B repeatedly generates drive signals for two cycles in the order of the second drive signal COM_B and the first drive signal COM_A. Yes. Then, the first drive signal generation unit 70A generates the first drive signal COM_A in the odd-numbered pixel period, and generates the second drive signal COM_B in the even-numbered pixel period. Further, the second drive signal generation unit 70B generates the second drive signal COM_B in the odd-numbered pixel period and generates the first drive signal COM_A in the even-numbered pixel period.

  As a result, every time ink for one pixel is ejected, the drive signals generated by the first drive signal generator 70A and the second drive signal generator 70B are interchanged. In other words, in the present embodiment, the drive signals generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B are interchanged for each latch signal LAT.

<About signal lines>
FIG. 17 is an explanatory diagram of signal lines for transmitting various signals. FIG. 18 is an explanatory diagram of a relationship between 2-bit pixel data input to the decoder 83 and the first switch control signal SW1 and the second switch control signal SW2 output from the decoder 83.

  The drive signal generation circuit 70 is connected to a first signal line COM_1 and a second signal line COM_2 that are signal lines for transmitting a drive signal. The first signal line COM_LINE1 transmits the drive signal generated by the first drive signal generator 70A, and the second signal line COM_LINE2 transmits the drive signal generated by the second drive signal generator 70B. The first signal line COM_LINE1 is connected to the first switch 87A, and the second signal line COM_LINE2 is connected to the second switch. For this reason, if the first switch 87A is turned on, the signal on the first signal line (the signal output from the first drive signal generator 70A) is input to the piezo element 417, and if the second switch 87B is turned on. The signal of the second signal line (the signal output from the second drive signal generation unit 70B) is input to the piezo element 417.

  The control logic 84 is connected to waveform selection signal lines q_LINE0 to q_LINE7 which are signal lines for transmitting the waveform selection signals q0 to q7. As will be described in detail later, the control logic 84 transmits the waveform selection signal q0 or the waveform selection signal q4 to the waveform selection signal line q_LINE0 and the waveform selection signal line q_LINE4, and transmits to the waveform selection signal line q_LINE1 and the waveform selection signal line q_LINE5. The waveform selection signal q1 or the waveform selection signal q5 is transmitted, the waveform selection signal q2 or the waveform selection signal q6 is transmitted to the waveform selection signal line q_LINE2 and the waveform selection signal line q_LINE6, and the waveform selection signal line q_LINE3 and the waveform selection signal line q_LINE7 are transmitted. The waveform selection signal q3 or the waveform selection signal q7 is transmitted.

  Next, the decoder 83 will be described. The decoder 83 includes a first decoding unit 83A and a second decoding unit 83B. The first decoding unit 83A has four AND gates 831A to 834A and one OR gate 835A.

  Each AND gate 831A to 834A of the first decoding unit 83A includes three input terminals and one output terminal. Each of the three input terminals has one of the waveform selection signal lines q_LINE0 to q_LINE3, the first latch circuit 82A in which the upper bits of the pixel data are latched, and the lower bits of the pixel data. It is connected to the second latch circuit 82B. Each of the AND gates 831A to 834A is different in the way of inputting the upper bit data and the lower bit data of the pixel data SI. That is, the AND gate 831A receives the signal of the waveform selection signal line q_LINE0, the inverted data of the upper bits of the pixel data SI, and the inverted data of the lower bits. Therefore, when the pixel data SI is data [00], the output from the AND gate 831A has contents according to the signal of the waveform selection signal line q_LINE0. The AND gate 832A receives the signal of the waveform selection signal line q_LINE1, the inverted data of the upper bits of the pixel data SI, and the lower bit data. For this reason, when the pixel data SI is data [01], the output from the AND gate 832A has contents according to the waveform selection signal line q_LINE1. In addition, the signal of the waveform selection signal line q_LINE2, the upper bit data of the pixel data SI, and the inverted data of the lower bit are input to the AND gate 833A. Therefore, when the pixel data SI is data [10], the output from the AND gate 832A has contents according to the waveform selection signal line q_LINE2. The AND gate 834A receives the signal of the waveform selection signal line q_LINE3, the upper bit data of the pixel data SI, and the lower bit data. For this reason, when the pixel data SI is data [11], the output from the AND gate 832A is in accordance with the signal of the waveform selection signal line q_LINE3.

  The OR gate 835A of the first decoding unit 83A includes four input terminals and one output terminal. The outputs from the AND gates 831A to 834A are input to each of the four input terminals. A first switch control signal SW1 is output from the OR gate 835A. That is, among the signals of the waveform selection signal line q_LINE0 to waveform selection signal line q_LINE3, the signal corresponding to the latched pixel data SI is selected and output as the first switch control signal SW1.

  The second decoding unit 83B has substantially the same configuration as the first decoding unit. Then, from the OR gate 835B of the second decoding unit 83B, the signal corresponding to the latched pixel data SI is selected from the signals of the waveform selection signal lines q_LINE4 to q_LINE7 and is output as the above-described second switch control signal SW2. The

  That is, the decoder 83 selects a signal corresponding to the latched pixel data SI from the signals of the waveform selection signal lines q_LINE0 to q_LINE3, and outputs the selected signal as the first switch control signal SW1. The decoder 83 selects one corresponding to the latched pixel data SI from the signals of the waveform selection signal lines q_LINE4 to q_LINE7, and outputs it as the second switch control signal SW1.

<Signal flowing through each signal line>
FIG. 19 is an explanatory diagram of a signal flowing through each signal line.
As already described, the first drive signal generation unit 70A generates the first drive signal COM_A in the odd-numbered pixel period, and generates the second drive signal COM_B in the even-numbered pixel period. Further, the second drive signal generation unit 70B generates the second drive signal COM_B in the odd-numbered pixel period and generates the first drive signal COM_A in the even-numbered pixel period.
Therefore, the first drive signal COM_A is transmitted to the first signal line COM_LINE1 in the odd pixel period, and the second drive signal COM_B is transmitted in the even pixel period. Further, the second drive signal COM_B is transmitted to the second signal line COM_LINE2 in the odd-numbered pixel period, and the first drive signal COM_A is transmitted in the even-numbered pixel period.

By the way, when the drive signals transmitted through the first signal line COM_LINE1 and the second signal line COM_LINE2 are interchanged in this way, the drive signals input to the first switch 87A and the second switch 87B are interchanged. The switch control signal SW1 and the switch control signal SW2 also need to be interchanged. (If the switch signal is not replaced, for example, in the case of pixel data “01” (small dot), the drive pulse PS5 of the second drive signal COM_B is applied instead of the drive pulse PS2 of the first drive signal COM_A. The amount of ink that does not correspond to the small dots is ejected.)
Therefore, the control logic 84 changes the signal output to each waveform selection signal line as the drive signal is switched. Specifically, the control logic 84 outputs the waveform selection signal q0 to the waveform selection signal line q_LINE0 in the odd-numbered pixel cycle and outputs the waveform selection signal q4 in the even-numbered pixel cycle. The control logic 84 outputs the waveform selection signal q1 to the waveform selection signal line q_LINE1 in the odd-numbered pixel period and the waveform selection signal q5 in the even-numbered pixel period. In addition, the control logic 84 outputs the waveform selection signal q2 to the waveform selection signal line q_LINE2 in the odd pixel period, and outputs the waveform selection signal q6 in the even pixel period. The control logic 84 outputs the waveform selection signal q3 to the waveform selection signal line q_LINE3 in the odd-numbered pixel period and the waveform selection signal q7 in the even-numbered pixel period. Further, the control logic 84 outputs the waveform selection signal q4 to the waveform selection signal line q_LINE4 in the odd pixel period and outputs the waveform selection signal q0 in the even pixel period. The control logic 84 outputs the waveform selection signal q5 to the waveform selection signal line q_LINE5 in the odd-numbered pixel period, and outputs the waveform selection signal q1 in the even-numbered pixel period. Further, the control logic 84 outputs the waveform selection signal q6 to the waveform selection signal line q_LINE6 in the odd pixel period and outputs the waveform selection signal q2 in the even pixel period. The control logic 84 outputs the waveform selection signal q7 to the waveform selection signal line q_LINE7 in the odd-numbered pixel period and the waveform selection signal q3 in the even-numbered pixel period. As described above, the waveform selection signals q0 to q3 and the waveform selection signals q4 to q7 output from the control logic 84 are exchanged with the exchange of the drive signal COM.
With the above processing, even when the drive signal COM is replaced, dots corresponding to the pixel data can be formed.

<Dot formation>
Next, in order to explain the effect of the present embodiment, the state of dot formation will be described. In the following description, it is assumed that the dots to be formed are only medium dots.

  20A and 20B are explanatory diagrams illustrating how dots are formed when there is no variation in the characteristics of the two drive signal generation units. 20A shows the position of the nozzle row and the state of dot formation in pass 1 to pass 4, and FIG. 20B shows the position of the nozzle row and the state of dot formation in pass 1 to pass 6. A pass refers to an operation (dot formation operation) in which ink is ejected from a moving nozzle to form dots. The pass n means the nth dot formation operation.

  For convenience of explanation, only one nozzle row of the nozzle rows that should be provided for each color is shown. The nozzle row includes eight nozzles (nozzle # 1 to nozzle # 8), but actually 180 nozzles. The nozzles indicated by black circles in the figure are nozzles that can eject ink. On the other hand, nozzles indicated by white circles are nozzles that cannot eject ink. Further, for convenience of explanation, the nozzle row is depicted as moving with respect to the paper, but this figure shows the relative position between the nozzle row and the paper. It has been moved in the transport direction. Also, for convenience of explanation, each nozzle is shown as having only a few dots (circles in the figure), but in reality, ink droplets are ejected intermittently from nozzles that move in the direction of movement. Therefore, a large number of dots are arranged in the moving direction. This row of dots is also called a raster line. A dot indicated by a black circle is a dot formed in the last pass, and a dot indicated by a white circle is a dot formed in a previous pass.

  Here, the nozzle pitch (interval between nozzles) is 1/180 inch. The dot pitch (interval between dots) is 1/720 inch. For this reason, the interval between raster lines is also 1/720 inch. Note that in this printing method, the pass and the transport operation are alternately repeated so that a raster line that is not recorded is sandwiched between raster lines that are recorded in one pass, and the rasters are continuously arranged in the transport direction. A line is formed. Here, three raster lines are sandwiched between raster lines formed in one pass.

  When there is no variation in the characteristics of the two drive signal generation units, every medium dot is formed with the same size. However, when the characteristics of the two drive signal generators vary, the size of the medium dots formed when the second drive signal generator 70B and the second drive signal COM_B are generated, and the first drive signal generator The size of the medium dots formed when 70A is generating the second drive signal COM_A is different. In the following description, it is assumed that the former is larger than the latter.

  FIG. 21 is an explanatory diagram of dot formation when the drive signals of the reference example described above are exchanged when the characteristics of the two drive signal generators vary. In the drawing, medium dots that are formed large (medium dots formed when the second drive signal COM_B is generated in the second drive signal generation unit 70B) are indicated by bold lines.

In the above-described reference example, the drive signal is switched for each dot forming operation (pass). Here, in the odd-numbered pass, the second drive signal generation unit 70B generates the second drive signal COM_B, and in the even-numbered pass, the first drive signal generation unit 70A generates the second drive signal COM_B. Shall.
In the case of the reference example, the thickness of each raster line is alternately different. As a result, a striped pattern along the moving direction is generated.

FIG. 22A is an explanatory diagram of dot formation when the drive signals are switched according to the present embodiment when there are variations in the characteristics of the two drive signal generation units. In this embodiment, the drive signal is exchanged during the dot forming operation for forming the raster line. Specifically, the second drive signal generation unit 70B generates the second drive signal COM_B in the odd-numbered pixel period, and the first drive signal generation unit generates the second drive signal COM_B in the even-numbered pixel period. .
According to the replacement of the drive signal of this embodiment, each raster line is configured by alternately arranging dots indicated by thin line circles and dots indicated by thick line circles. Thereby, the thickness of each raster line becomes the same thickness, and generation | occurrence | production of the striped pattern along a moving direction can be suppressed.

FIG. 22B is an explanatory diagram of an improved example of drive signal replacement according to the present embodiment. In this improved example, the drive signals are exchanged during the dot formation operation for forming the raster line, and the order of the drive signals generated by each drive signal generation unit is changed for each dot formation operation (pass). Specifically, in the odd-numbered pass, the second drive signal generation unit 70B generates the second drive signal COM_B in the odd pixel period, and the first drive signal generation unit 70A generates the second drive signal COM_B in the even pixel period. Is generated. On the other hand, in the even-numbered pass, the first drive signal generation unit 70A generates the second drive signal COM_B in the odd-numbered pixel cycle, and the second drive signal generation unit generates the second drive signal COM_B in the even-numbered pixel cycle. .
According to the replacement of the drive signal of this improved example, the thickness of each raster line becomes the same, and the occurrence of a striped pattern along the moving direction can be suppressed. In addition, according to the replacement of the drive signal in this improved example, the medium dots (dots indicated by bold lines in the drawing) that are formed large are not adjacent in the transport direction. For this reason, compared with the case of FIG. 22A, an image quality becomes uniform and an image quality improves.

=== Other Embodiments ===
The above-described embodiment is mainly described for a printer. Among them, a printing apparatus, a recording apparatus, a liquid ejection apparatus, a printing method, a recording method, a liquid ejection method, a printing system, a recording system, and a computer system are included. Needless to say, the disclosure includes a program, a storage medium storing the program, a display screen, a screen display method, a printed material manufacturing method, and the like.

  Moreover, although the printer etc. as one embodiment were demonstrated, said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this 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 drive signal>
In the above-described embodiment, the first waveform portion SS11a to the third waveform portion SS13a of the first drive signal COM_A are set to the same time width as the first waveform portion SS21a to the third waveform portion SS23a of the second drive signal COM_B. ing. Accordingly, the first change signal CH_A for the first drive signal COM_A and the second change signal CH_B for the second drive signal COM_B are aligned at the H level. However, the drive signal and the change signal are not limited to this.

  FIG. 23 is an explanatory diagram of another embodiment of various signals. In the figure, the first drive signal COM_A, the second drive signal COM_B, the head control signal (LAT signal, the first change signal CH_A, the second change signal CH_B), the waveform selection signals q0 to q7, and the piezo elements are applied. Signal is shown. In this embodiment, the timings at which the first change signal CH_A and the second change signal CH_B are at the H level are not aligned. The waveform selection signals q0 to q3 are generated by the control logic 84 based on the latch signal LAT and the first change signal CH_A. The waveform selection signals q4 to q7 are generated by the control logic 84 based on the latch signal LAT and the second change signal CH_A. Thereby, a signal corresponding to the pixel data is applied to the piezo element to form a dot.

  In this embodiment, when small dots and medium dots are formed, heat generation is biased toward the transistor pair of the drive signal generation unit that generates the second drive signal COM_B. For this reason, in this embodiment, if the drive signals are exchanged, the heat generation of the transistor pair 721A of the first drive signal generation unit 70A and the transistor pair 721B of the second drive signal generation unit 70B becomes equal.

  In this embodiment, when large dots are formed, the transistor pair 721A of the first drive signal generation unit 70A and the transistor pair 721B of the second drive signal generation unit 70B are evenly arranged without switching the drive signals. Fever. Therefore, when printing a text image mainly composed of large dots, the drive signal is not replaced. When a photographic image mainly composed of small dots or medium dots is printed, the drive signal is interchanged. May be performed. That is, in this embodiment, the CPU 62 may determine whether or not to replace the drive signal according to the type of image to be printed.

<About the timing of the drive signal replacement>
According to the above-described embodiment, the drive signal generated by each drive signal generator is replaced for each latch signal LAT. In other words, according to the above-described embodiment, each time the carriage CR moves by 1/720 inch corresponding to one pixel, the drive signal generated by each drive signal generation unit is replaced. However, even if the timing is not such, if the drive signal is exchanged during the dot forming operation for forming the raster line, it is possible to suppress the deterioration in image quality caused by the difference in the thickness of the raster line.

  FIG. 24 is an explanatory diagram of a drive signal generated by each drive signal generation unit of another embodiment. As described above, the drive signals generated by the respective drive signal generation units may be interchanged for each detection signal PTS. In other words, every time the carriage CR moves by 1/360 inch corresponding to two pixels, the drive signals generated by the first drive signal generator 70A and the second drive signal generator 70B may be interchanged.

  FIG. 25 is an explanatory diagram of drive signals generated by each drive signal generation unit of still another embodiment. Even if the drive signal is not periodically replaced as in the above-described embodiment, if the drive signal is replaced at an arbitrary timing during the dot forming operation, the difference occurs in the raster line thickness. A decrease in image quality can be suppressed.

<About the drive signal generator>
In the above-described embodiment, the number of drive signal generation units is two. However, it is not limited to this. The drive signal generation circuit may include two or more drive signal generation units. At a certain timing, the first drive signal generation unit 70A generates the first drive signal COM_A, the second drive signal generation unit 70B generates the second drive signal COM_B, and the third drive signal generation unit generates the third drive signal. The first drive signal generator 70A generates the second drive signal COM_B, the second drive signal generator 70B generates the first drive signal COM_A, and the third drive signal generator Three drive signals may be generated. Even in such a case, since the drive signals generated by the first drive signal generation unit and the second drive signal generation unit are interchanged as in the above-described embodiment, the same effect as in the above-described embodiment can be obtained. .

<Replacement of drive signal>
In the above-described embodiment, the first drive signal generation unit 70A generates the first drive signal COM_A at a certain timing, the second drive signal generation unit 70B generates the second drive signal COM_B, and the first drive at another timing. The signal generation unit 70A generates the second drive signal COM_B, and the second drive signal generation unit 70B generates the first drive signal COM_A. That is, according to the above-described embodiment, the drive signal generated by the first drive signal and the drive signal generated by the second drive signal are interchanged.

  However, it is not always necessary to replace the drive signals. For example, when a third drive signal generation unit different from the first drive signal generation unit 70A and the second drive signal generation unit is provided, the first drive signal generation unit 70A outputs the first drive signal COM_A at a certain timing. The second drive signal generator 70B generates the second drive signal COM_B, the third drive signal generator generates the third drive signal, and the first drive signal generator 70A performs the second drive at another timing. The signal COM_B may be generated, the second drive signal generation unit 70B may generate the third drive signal, and the third drive signal generation unit may generate the first drive signal COM_A.

  Thus, even when the drive signal to be generated is rotated between the three drive signal generation units, the drive signal generation unit that generates the first drive signal is changed as in the above-described embodiment. Yes. For this reason, for example, when forming small dots, the first drive signal generation unit 70A generates the first drive signal COM_A before the change, so that the first drive signal generation unit 70A consumes power, and the second drive after the change. Since the signal generator 70B generates the first drive signal COM_A, power is consumed in the second drive signal generator 70B. Accordingly, by changing the drive signal generation unit that generates the first drive signal COM_A, the first drive signal generation unit 70A and the second drive signal generation unit 70B generate heat equally. In addition, even if the characteristics of the drive signal generators vary, small dots having different sizes are mixed by changing the drive signal generator that generates the drive signal COM_A during the dot formation operation. Therefore, the image quality becomes uniform and the image quality is improved.

<About the printer>
In the above-described embodiment, the printer has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technique as that of the present embodiment may be applied to various recording apparatuses to which an ink jet technique is applied such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application. Even if this technology is applied to such a field, the liquid can be directly ejected (directly drawn) toward the object. You can go down.

<About ink>
Since the above-described embodiment is an embodiment of a printer, dye ink or pigment ink is ejected from the nozzle. However, the liquid ejected from the nozzle is not limited to such ink. For example, liquids (including water) including metal materials, organic materials (especially polymer materials), magnetic materials, conductive materials, wiring materials, film-forming materials, electronic inks, processing liquids, gene solutions, etc. are ejected from nozzles. May be. If such a liquid is directly discharged toward the object, material saving, process saving, and cost reduction can be achieved.

<About nozzle>
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.

=== Summary ===
(1) The printer (an example of a printing apparatus) includes a piezo element 417 (an example of an element) that is driven to form dots and a first drive that generates a drive signal COM for driving the piezo element 417. A signal generation unit 70A, a second drive signal generation unit 70B, and a controller including a printer-side controller 60 and a head control unit HC;

  The printer-side controller 60 inputs DAC values to the first drive signal generation unit 70A and the second drive signal generation unit 70B, respectively, and sends drive signals to the first drive signal generation unit 70A and the second drive signal generation unit 70B. It is generated. For example, when forming a dot in a certain dot formation operation (S30, see FIG. 11), the printer-side controller 60 causes the first drive signal generation unit 70A to generate the first drive signal COM_A, thereby generating the second drive signal. The generation unit 70B is caused to generate the second drive signal COM_B.

  Here, for example, when forming a small dot, only the drive pulse PS2 of the first drive signal COM_A generated by the first drive signal generator 70A is applied to the piezo element 417 (see FIG. 9). For this reason, for example, when forming small dots, power is consumed only by the first drive signal generation unit 70A that generates the first drive signal COM_A, and power is consumed by the second drive signal generation unit 70B that generates the second drive signal COM_B. Is not consumed (see FIG. 13). Thus, when forming dots of a predetermined size, the power consumption of the first drive signal generation unit 70A and the power consumption of the second drive signal generation unit 70B are different.

  And the fact that the power consumption is different means that the heat generation amount is different. Therefore, when the first drive signal generation unit 70A continues to generate the first drive signal COM_A and the second drive signal generation unit 70B continues to generate the second drive signal COM_B, the first drive signal generation unit 70A The drive signal generator 70B generates heat biased.

  Therefore, in the above printing apparatus, the printer-side controller 60 replaces the drive signal COM generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B, and performs the second drive by the first drive signal generation unit 70A. The signal COM_B is generated, and the first drive signal COM_A is generated by the second drive signal generation unit 70B. Accordingly, for example, when forming small dots, power is consumed only by the second drive signal generation unit 70B that generates the first drive signal COM_A, and the second drive signal generation unit 70B generates the first drive signal. Heat is generated from the portion 70A. However, when the heat generation before and after the switching of the drive signals is viewed comprehensively, the first drive signal generation unit 70A and the second drive signal generation unit 70B generate heat equally.

  However, when the drive signal is replaced for each dot forming operation as in the reference example, the thickness of each raster line is different as shown in FIG. As a result, the image quality of the printed image may be degraded.

  Therefore, in the printer described above, as shown in FIG. 16 (or FIG. 24 or FIG. 25), the printer-side controller 60 has the first drive signal generation unit 70A and the second drive signal generation unit 70B during the dot formation operation. The generated drive signal COM is exchanged. Accordingly, in the raster line, 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, the dots formed This includes the dots formed when the first drive signal generation unit 70A generates the second drive signal COM_B and the second drive signal generation unit 70B generates the first drive signal COM_A. As a result, as shown in FIGS. 22A and 22B, it is possible to suppress deterioration in image quality caused by the difference in the thickness of the raster lines.

(2) In the above-described embodiment, the first drive signal generator 70A generates the first drive signal COM_A at a certain timing, the second drive signal generator 70B generates the second drive signal COM_B, and at another timing. The first drive signal generator 70A generates the second drive signal COM_B, and the second drive signal generator 70B generates the first drive signal COM_A. That is, according to the above-described embodiment, the drive signal generated by the first drive signal and the drive signal generated by the second drive signal are interchanged. As a result, the first drive signal generator 70A and the second drive signal generator 70B generate heat equally. Further, by replacing the drive signal COM during the dot forming operation, it is possible to suppress deterioration in image quality caused by the difference in the raster line thickness.

  Note that the drive signal generation circuit may include two or more drive signal generation units, for example, three drive signal generation units. At a certain timing, the first drive signal generation unit 70A generates the first drive signal COM_A, the second drive signal generation unit 70B generates the second drive signal COM_B, and the third drive signal generation unit generates the third drive signal. The first drive signal generator 70A generates the second drive signal COM_B, the second drive signal generator 70B generates the first drive signal COM_A, and the third drive signal generator Three drive signals may be generated. Even in such a case, since the drive signals generated by the first drive signal generation unit and the second drive signal generation unit are interchanged, the same effect as the above-described embodiment can be obtained.

(3) In the above-described embodiment, the drive signal generated by the first drive signal and the drive signal generated by the second drive signal are interchanged. However, the drive signal does not necessarily have to be interchanged. For example, when a third drive signal generation unit different from the first drive signal generation unit 70A and the second drive signal generation unit is provided, the first drive signal generation unit 70A outputs the first drive signal COM_A at a certain timing. The second drive signal generator 70B generates the second drive signal COM_B, the third drive signal generator generates the third drive signal, and the first drive signal generator 70A performs the second drive at another timing. The signal COM_B may be generated, the second drive signal generation unit 70B may generate the third drive signal, and the third drive signal generation unit may generate the first drive signal COM_A. Thus, even when the drive signal to be generated is rotated between the three drive signal generation units, the drive signal generation unit that generates the first drive signal is changed as in the above-described embodiment. Therefore, the image quality becomes uniform and the image quality is improved.

(4) In the above-described printer, the printer-side controller 60 is in each cycle in which dots for one pixel are formed, that is, every time the carriage CR moves 1/720 inch when performing printing at a resolution of 720 dpi. The drive signals generated by the first drive signal generator 70A and the second drive signal generator 70B are interchanged (see FIG. 16). If the drive signals are switched at such timing, the first drive signal generator 70A is generated when the first drive signal COM_A is generated and the second drive signal generator 70B is generating the second drive signal COM_B. The dots and the dots formed when the first drive signal generation unit 70A generates the second drive signal COM_B and the second drive signal generation unit 70B generates the first drive signal COM_A along the moving direction. It is formed alternately. Thereby, the difference in the raster line thickness becomes inconspicuous, and deterioration of the image quality can be further suppressed.

  Note that the drive signal replacement timing is not limited to each period in which dots for one pixel are formed. For example, as shown in FIG. 24, it may be every cycle in which dots are formed for two pixels, or at any timing during the dot forming operation as shown in FIG.

(5) The printer described above includes a carriage CR (an example of a moving body that moves the element in the moving direction to change the relative position between the element and the medium) and a linear encoder 51 (an example of a sensor that detects the position of the moving body). ). The above-described printer-side controller 60 performs the first drive in accordance with the latch signal LAT based on the detection signal PTS output from the linear encoder 51 or according to the detection signal PTS output from the linear encoder 51. The drive signals COM generated by the signal generator 70A and the second drive signal generator 70B are interchanged. Thereby, the printer-side controller can acquire the timing at which the drive signal should be replaced.

(6) As shown in FIG. 22B, the printer-side controller 60 changes the order of the drive signals generated by the drive signal generators for each dot forming operation. Accordingly, the dots formed when 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 are continuously arranged in the transport direction. Or the dots formed when the first drive signal generator 70A generates the second drive signal COM_B and the second drive signal generator 70B generates the first drive signal COM_A are continuously arranged in the transport direction. Is suppressed. For this reason, the image quality of the printed image becomes uniform and the image quality is improved.

(7) The above printer can form large dots, medium dots, and small dots. The head controller HC selectively applies a drive pulse included in the first drive signal COM_A or the second drive signal COM_B to the piezo element 417 according to the size of the dot to be formed. For example, when the pixel data is “01”, since the dot to be formed is a small dot, the head controller HC inputs the waveform selection signal q1 to the first switch 87A as the first switch signal SW1, and controls the second switch. The waveform selection signal q5 is input to the second switch 87B as the signal SW2. As a result, the head controller HC applies the drive pulse PS2 of the first drive signal COM_A to the piezo element 417.

(8) When forming a large dot, the drive pulse PS1, the drive pulse PS5, and the drive pulse PS3 are applied to the piezo element 417. By the way, for example, when the first drive signal generation unit 70A generates a drive pulse PS1 for forming a large dot, the second drive signal generation unit 70B generates a drive pulse PS4 for forming a medium dot. Yes. Thus, when one drive signal generator generates a drive pulse for forming a dot of a certain size, the other drive signal generator generates a drive pulse for forming a dot of another size. By doing so, the period T shown in FIG. 9 can be shortened. As a result, the printing resolution is improved, and the carriage moving speed can be increased, so that the printing speed is improved.

(9) When forming the large dot, the head controller HC applies the drive pulse PS1 and the drive pulse PS3 included in the first drive signal COM_A to the piezo element 417, and is included in the second drive signal COM_B. A drive pulse PS5 is applied to the piezo element 417.
If the first drive signal COM_A has a drive pulse PS5 instead of the drive pulse PS2 and a large dot is formed only by the first drive signal COM_A, one drive signal generation that generates the first drive signal COM_A The unit consumes 4.5 W of power, and the other drive signal generator does not consume power. As a result, heat generation is biased to one drive signal generation unit that generates the first drive signal COM_A.
On the other hand, in the head controller HC, three drive pulses for forming a large dot are dispersed in the first drive signal COM_A and the second drive signal COM_B. As a result, when a large dot is formed, the drive signal generation unit that generates the first drive signal COM_A consumes 3.0 W of power, and the drive signal generation unit that generates the second drive signal COM_B has 1.5 W of power. Consume power. That is, it is possible to reduce the deviation of the heat generation amount in one dot forming operation.

(10) It is desirable to include all the components of the above-described embodiment because all the effects can be achieved. However, it goes without saying that not all the components of the above-described embodiment are essential.

(11) In the printing method described above, first, a printer having the piezo element 417, the first drive signal generation unit 70A, and the second drive signal generation unit 70B is prepared. When printing is performed, at a certain timing, 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 to obtain a predetermined size. Forming dots. At another timing, the first drive signal generator 70A generates the second drive signal COM_B, and the second drive signal generator 70B generates the first drive signal COM_A to form dots of a predetermined size. .
As shown in FIG. 16 (or FIG. 24 and FIG. 25), the printer-side controller 60 generates the drive signal COM generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B during the dot formation operation. Have been replaced. As a result, as shown in FIGS. 22A and 22B, it is possible to suppress deterioration in image quality caused by the difference in the thickness of the raster lines.

  The printing method is not limited to the method of exchanging the drive signals generated by the two drive signal generation units. For example, a printing method in which a drive signal to be generated is rotated between three drive signal generation units may be used.

(12) The printer described above includes the piezo element 417, the first drive signal generation unit 70A, and the second drive signal generation unit 70B. In addition, the printer is provided with a memory 63, and the memory 63 stores a program. The CPU 62 of the printer inputs the DAC value to the first drive signal generation unit 70A and the second drive signal generation unit 70B according to this program.
Specifically, this program causes the CPU 62 of the printer to input a DAC value so that the first drive signal COM_A is generated by the first drive signal generator 70A at a certain timing, and the second drive signal generator 70B. Then, the DAC value is input so as to generate the second drive signal COM_B. In addition, this program causes the CPU 62 of the printer to input a DAC value so that the first drive signal generation unit 70A generates the second drive signal COM_B at another timing, and the second drive signal generation unit 70B outputs the second drive signal COM_B. The DAC value is input so as to generate one drive signal COM_A.
This program causes the CPU 62 of the printer to exchange the drive signals COM generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B during the dot formation operation. This allows the printer to print with high image quality.

  Note that the program is not limited to a program that causes the printer to replace the drive signals generated by the two drive signal generation units. For example, the program may cause the printer to rotate the generated drive signal between the three drive signal generators.

(13) The above printing system includes a computer and a printer. According to such a printing system, when the printer performs printing based on print data from the computer, the drive generated by the first drive signal generation unit 70A and the second drive signal generation unit 70B during the dot formation operation. Since the signal COM can be exchanged, high-quality printing can be performed.

  Note that the printing system is not limited to one that replaces the drive signals generated by the two drive signal generation units. For example, a printing system that rotates a drive signal to be generated between three drive signal generation units may be used.

1 is a diagram illustrating a configuration of a printing system. FIG. 2A is a block diagram illustrating configurations of a computer and a printer. FIG. 2B is a diagram schematically illustrating a part of the memory included in the printer. FIG. 3A is a diagram illustrating a configuration of the printer according to the present embodiment. FIG. 3B is a side view illustrating the configuration of the printer according to the present embodiment. It is a block diagram explaining the structure of a drive signal generation circuit. FIG. 5A is a block diagram for explaining the configuration of the first waveform generation circuit and the second waveform generation circuit. FIG. 5B is a diagram illustrating the relationship between the DAC value input to the D / A converter and the output voltage from the voltage amplifier circuit. FIG. 6A is a diagram for explaining a part of the generated drive signal. FIG. 6B is a diagram for explaining the operation of dropping the output voltage of the first current amplifier circuit from the voltage V1 to the voltage V4. 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. It is a block diagram explaining the structure of the head control part HC. It is a figure explaining 1st drive signal COM_A, 2nd drive signal COM_B, a head control signal, and waveform selection signals q0-q7. 5 is a diagram for explaining a waveform portion applied to a piezo element 417. FIG. It is a flowchart explaining printing operation. It is explanatory drawing of the relationship between drive pulse PS1 and power consumption. It is explanatory drawing of the relationship between 1st drive signal COM_A and 2nd drive signal COM_B, and power consumption. It is a figure which shows another example of a process when replacing a drive signal. FIG. 15A is a diagram illustrating the drive pulse PS2 generated by the first drive signal generation unit 70A. FIG. 15B is a diagram illustrating a relationship between the DAC value input to the first drive signal generation unit 70A and the output voltage. FIG. 15C is a diagram illustrating the drive pulse PS2 generated by the second drive signal generation unit 70B. FIG. 15D is a diagram illustrating a relationship between the DAC value input to the second drive signal generation unit 70B and the output voltage. It is explanatory drawing of the drive signal which each drive signal generation part of this embodiment produces | generates. It is explanatory drawing of the signal wire | line which transmits various signals. It is explanatory drawing of the relationship between 2-bit pixel data, 1st switch control signal SW1, and 2nd switch control signal SW2. It is explanatory drawing of the signal which flows into each signal line. 20A and 20B are explanatory diagrams illustrating how dots are formed when there is no variation in the characteristics of the two drive signal generation units. It is explanatory drawing of dot formation at the time of exchanging the drive signal of the above-mentioned reference example, when the characteristic of two drive signal generation parts has dispersion | variation. FIG. 22A is an explanatory diagram of dot formation when the drive signals are switched according to the present embodiment when there are variations in the characteristics of the two drive signal generation units. FIG. 22B is an explanatory diagram of an improved example. It is explanatory drawing of another embodiment of various signals. It is explanatory drawing of the drive signal which each drive signal generation part of another embodiment produces | generates. It is explanatory drawing of the drive signal which each drive signal generation part of another embodiment produces | generates.

Explanation of symbols

1 Printer, S paper,
20 paper transport mechanism, 21 paper feed roller, 22 transport motor, 23 transport roller,
24 platen, 25 paper discharge roller,
30 Carriage moving mechanism, 31 Carriage motor, 32 Guide shaft,
33 Timing belt, 34 Drive pulley, 35 Drive pulley,
40 head units, 41 heads, HC head control unit,
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 generator, 70B second drive signal generator,
71A first waveform generation circuit, 71B second waveform generation circuit,
711A D / A converter, 711B D / A converter, 712A voltage amplification circuit,
712B voltage amplification circuit, 72A first current amplification circuit, 72B second current amplification circuit,
721A first transistor pair, 721B second transistor pair,
Q1 NPN type transistor, Q2 PNP type transistor,
722 heat sink,
81A first shift register, 81B second shift register,
82A first latch circuit, 82B second latch circuit,
83 decoder, 84 control logic,
87A first switch, 87B second switch,
100 printing system, 110 computer, 111 host side controller,
112 interface unit, 113 CPU, 114 memory,
120 display device, 130 input device, 131 keyboard, 132 mouse,
140 recording / reproducing apparatus, 141 flexible disk drive apparatus,
142 CD-ROM drive device,
COM_A first drive signal, COM_B second drive signal,
LAT latch signal, CH_A first change signal, CH_B second change signal,
q0 to q7 waveform selection signal,
COM_LINE1 first signal line, COM_LINE2 second signal line,
q_LINE0 to q_LINE7 Waveform selection signal line

Claims (7)

(A) an element driven to form a dot;
(B) a first drive signal generation unit that generates a drive signal for driving the element and transmits the drive signal to the first signal line;
(C) a second drive signal generation unit that generates a drive signal for driving the element that can be driven by the drive signal generated by the first drive signal generation unit and transmits the drive signal to the second signal line; When,
(D) When forming dots of a predetermined size at a certain timing, the first drive signal generator generates a first drive signal;
When forming the dot of the predetermined size at another timing, the second drive signal generation unit generates the first drive signal,
A controller that controls driving of the element by applying a signal selected from the driving signal of the first signal line and the driving signal of the second signal line to the element;
A printing apparatus having (E),
(F) The printing apparatus alternately repeats a dot forming operation for forming dots on the medium while changing a relative position between the element and the medium, and a transport operation for transporting the medium.
(G) The controller changes a drive signal generation unit that generates the first drive signal from the first drive signal generation unit to the second drive signal generation unit during the dot formation operation. Printing device. The printing apparatus according to claim 1,
When forming the dot of the predetermined size at the certain timing, the controller causes the first drive signal generation unit to generate the first drive signal and the second drive signal generation unit to generate the second drive signal. Generated,
When forming the dots of the predetermined size at the different timing, the controller generates the first drive signal at the second drive signal generation unit and the second drive at the first drive signal generation unit. A printing apparatus characterized by generating a signal. The printing apparatus according to claim 1,
The printing apparatus further includes a drive signal generation unit different from the first drive signal generation unit and the second drive signal generation unit,
When forming the dot of the predetermined size at the certain timing, the controller causes the first drive signal generation unit to generate the first drive signal and the second drive signal generation unit to generate the second drive signal. Generated,
When forming the dots of the predetermined size at the different timing, the controller causes the second drive signal generation unit to generate the first drive signal and the another drive signal generation unit to generate the second drive. A printing apparatus characterized by generating a signal. The printing apparatus according to any one of claims 1 to 3,
The printing apparatus according to claim 1, wherein the controller changes a drive signal generation unit that generates the first drive signal for each period in which dots for one pixel are formed. The printing apparatus according to any one of claims 1 to 4,
The printing apparatus includes a moving body that moves the element in a moving direction to change a relative position between the element and the medium, and a sensor that detects a position of the moving body,
The printing apparatus, wherein the controller changes a drive signal generation unit that generates the first drive signal in accordance with a detection result of the sensor. An element driven to form a dot, a first drive signal generating unit that generates a drive signal for driving the element, and transmits the drive signal to a first signal line, and the first drive signal generation And a second drive signal generation unit that generates a drive signal for driving the element that can be driven by the drive signal generated by the unit and transmits the drive signal to the second signal line. ,
When forming dots of a predetermined size at a certain timing, the first drive signal generation unit generates a first drive signal,
When forming the dot of the predetermined size at another timing, the second drive signal generation unit generates the first drive signal,
A printing method for controlling driving of the element by applying a signal selected from the driving signal of the first signal line and the driving signal of the second signal line to the element,
A dot forming operation for forming dots on the medium while changing a relative position between the element and the medium and a transport operation for transporting the medium are alternately repeated.
A printing method, wherein a drive signal generation unit that generates the first drive signal is changed from the first drive signal generation unit to the second drive signal generation unit during the dot forming operation. A printing system comprising a computer and a printing device,
The printing apparatus includes:
(A) an element driven to form a dot;
(B) a first drive signal generation unit that generates a drive signal for driving the element and transmits the drive signal to the first signal line;
(C) a second drive signal generation unit that generates a drive signal for driving the element that can be driven by the drive signal generated by the first drive signal generation unit and transmits the drive signal to the second signal line; When,
(D) When forming dots of a predetermined size at a certain timing, the first drive signal generator generates a first drive signal;
When forming the dot of the predetermined size at another timing, the second drive signal generation unit generates the first drive signal,
A controller that controls driving of the element by applying a signal selected from the driving signal of the first signal line and the driving signal of the second signal line to the element;
Have
The printing apparatus repeats alternately a dot forming operation for forming dots on the medium while changing a relative position between the element and the medium, and a transport operation for transporting the medium,
The controller changes a drive signal generation unit that generates the first drive signal from the first drive signal generation unit to the second drive signal generation unit during the dot formation operation.

Images