JP5742351B2 - Liquid ejecting apparatus and liquid ejecting method - Google Patents

Description

  The present invention relates to a liquid ejection device and a liquid ejection method.

  2. Description of the Related Art Liquid ejecting apparatuses that record an image or the like by ejecting liquid from a head unit and landing droplets (dots) on a medium are widely used. As a method of ejecting liquid from the head unit, a method of ejecting liquid by applying a drive waveform signal to an element such as a piezoelectric element provided inside the head unit and vibrating the piezoelectric element is known. ing.

  In such a liquid ejecting apparatus, a voltage signal having a small amplitude is input to a head unit via a cable such as a flexible flat cable (FFC) from a control unit that generates a predetermined voltage signal. A method of generating a drive waveform signal by amplification is proposed. (For example, patent document 1).

JP 2000-343690 A

  According to the method of Patent Document 1, since it is not necessary to pass a current having a large peak through a cable such as FFC, heat generation in the cable can be reduced, and the number of FFC cores can be reduced. By the way, when such a small amplitude drive signal is generated, there is a method of generating a drive signal by converting a digital signal into an analog waveform signal using a D / A conversion circuit (digital-analog converter). It is common. On the other hand, the drive signal generated by the D / A conversion circuit often has insufficient accuracy as it is. Therefore, in order to generate a highly accurate drive signal and to accurately eject liquid, it is necessary to perform operations such as trimming for each apparatus in the manufacturing (inspection) process of the liquid ejecting apparatus, resulting in an increase in cost. .

  An object of the present invention is to generate a drive signal with high accuracy at a low cost in a liquid ejecting apparatus to eject liquid.

The main invention for achieving the above object is: (A) a control unit that generates an analog voltage signal based on a digital signal that defines the waveform shape of a signal; and (B) a voltage amplification unit that amplifies the analog voltage signal. When a current amplifier for generating a drive signal to the current amplifying said analog voltage signal whose voltage has been amplified, is driven by the driving signal, it possesses a plurality of elements for ejecting liquid from a nozzle, and the current amplification A head unit provided in each of the plurality of elements , (C) a transmission unit that transmits the analog voltage signal from the control unit to the head unit, (D) after voltage amplification, and A storage unit that stores a value obtained by measuring the voltage of the analog voltage signal before current amplification, wherein the control unit stores the value stored in the storage unit. The Change the digital signal have a liquid ejection apparatus characterized by generating said analog voltage signal based on the digital signal.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a block diagram illustrating an overall configuration of a printer. FIG. 2A is a diagram illustrating the configuration of the printer according to the present embodiment. FIG. 2B is a side view illustrating the configuration of the printer according to the present embodiment. It is sectional drawing for demonstrating the structure of a head. It is a figure explaining the composition and operation of head control part HC. It is a figure explaining the drive signal COM. It is a figure explaining a part of analog voltage signal COM '. It is a figure explaining the operation | movement which drops the analog voltage signal COM 'after voltage amplification from the voltage V1 to the voltage V4. It is a figure showing the flow of the setting operation | work for changing a DAC value in 1st Embodiment. It is a figure explaining the voltage measurement in 1st Embodiment. It is a figure showing the flow of the setting operation | work for changing a DAC value in 2nd Embodiment. It is a figure explaining the voltage measurement in 2nd Embodiment.

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

(A) a control unit that generates an analog voltage signal based on a digital signal that defines the waveform shape of the signal, (B) a voltage amplification unit that amplifies the analog voltage signal, and the voltage amplified analog voltage signal A current amplifier that amplifies the current to generate a drive signal; a head that is driven by the drive signal and that ejects liquid from a nozzle; and (C) the analog voltage signal from the controller. A liquid jet comprising: a transmission unit that transmits to the head unit; and (D) a storage unit that stores a value obtained by measuring the voltage of the analog voltage signal after voltage amplification and before current amplification. An apparatus, wherein the control unit changes the digital signal using the value stored in the storage unit, and generates the analog voltage signal based on the digital signal. Liquid ejecting apparatus.
According to such a liquid ejecting apparatus, the liquid ejecting apparatus can generate a drive signal with high accuracy at low cost and eject liquid.

In the liquid ejecting apparatus, the storage unit is voltage-amplified with a maximum value and a minimum value of the actually measured voltage of the analog voltage signal after voltage amplification and before current amplification. And a correction value calculated based on the relationship between the theoretical maximum and minimum values of the analog voltage signal before current amplification, and the control unit stores the correction It is desirable to change the digital signal by multiplying the digital signal by a value.
According to such a liquid ejection device, the DAC value can be corrected only by measuring the voltage of the analog voltage signal COM ′ to be generated at two points, so that an accurate drive signal COM can be generated at a lower cost. can do.

In such a liquid ejection device, the storage unit stores the highest value and the lowest value of the actually measured voltage of the analog voltage signal after voltage amplification and before current amplification, The control unit obtains a relationship between the magnitude of the digital signal and the magnitude of the voltage of the analog voltage signal generated based on the digital signal from the stored maximum and minimum values of the voltage, and It is desirable to change the digital signal based on it.
According to such a liquid ejecting apparatus, an analog voltage signal having an arbitrary voltage value can be output with high accuracy, so that an accurate drive signal COM can be generated at low cost.

In the liquid ejecting apparatus, it is preferable that the voltage of the analog voltage signal generated based on the digital signal after the change is larger than a ground voltage.
According to such a liquid ejecting apparatus, only a voltage signal in a range in which it can operate normally can be input to the head control unit HC, so that malfunction in the head control unit can be suppressed.

In this liquid ejection apparatus, the control unit includes a chip in which a digital signal generation unit that generates the digital signal and an analog voltage signal generation unit that generates the analog voltage signal are integrally formed. Is desirable.
According to such a liquid ejecting apparatus, since it is less likely to be affected by noise in the process of transmitting a digital signal (DAC value), it is easy to generate a drive signal COM having an accurate waveform shape.

  Further, the control unit generates an analog voltage signal based on a digital signal that defines the waveform shape of the signal, transmits the analog voltage signal from the control unit to the head unit, and in the head unit, Amplifying the analog voltage signal; generating a drive signal by amplifying the analog voltage signal that has been voltage amplified; driving the element by the drive signal; and ejecting liquid from the nozzle; A value obtained by measuring the voltage of the analog voltage signal after voltage amplification and before current amplification is stored in a storage unit, and the digital value is stored using the value stored in the storage unit. A liquid ejection method comprising changing a signal and generating the analog voltage signal based on the digital signal becomes apparent.

=== Basic configuration of liquid ejection device ===
An ink jet printer (printer 1) will be described as an example as a form of a liquid ejection device for carrying out the invention.

<Printer configuration>
FIG. 1 is a block diagram illustrating the overall configuration of the printer 1. The printer 1 is a liquid ejection device that records (prints) characters and images on a medium such as paper, cloth, and film, and is connected to a computer 110 that is an external device so as to be communicable.

  A printer driver is installed in the computer 110. The printer driver is a program for displaying a user interface on a display device (not shown) and converting image data output from an application program into print data. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Also, the printer driver can be downloaded to the computer 110 via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions.

  The computer 110 outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image. The print data is data in a format that can be interpreted by the printer 1 and includes various command data and pixel data SI. 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 SI is data related to the pixels of the image to be printed. Here, a pixel is a unit element constituting an image, and an image is formed by arranging these pixels two-dimensionally. The pixel data SI in the print data is data (for example, gradation values) related to dots formed on a medium (for example, paper S). The pixel data is composed of, for example, 2-bit data for each pixel. This 2-bit pixel data can represent one pixel in four gradations. That is, there is data [00] corresponding to no dot, data [01] corresponding to small dots, data [10] corresponding to medium dots, and data [11] corresponding to large dots.

  The printer 1 includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, a controller 60, and a transmission unit 70. The controller 60 controls each unit such as the head unit 40 based on print data received from the computer 110 which is an external device, and prints an image on a medium. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

<Transport unit 20>
FIG. 2A is a schematic bird's-eye view showing the configuration of the printer 1 of this embodiment, and FIG. 2B is a schematic side view showing the configuration of the printer 1.

  The transport unit 20 is for transporting a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction). Here, the conveyance direction is a direction that intersects the direction in which the carriage moves. The transport unit 20 includes a paper feed roller 21, a transport motor 22, a transport roller 23, a platen 24, and a paper discharge roller 25 (FIGS. 2A and 2B).

  The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable region, and is driven by the transport motor 22. The operation of the transport motor 22 is controlled by a controller 60 on the printer side. 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 discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area.

<Carriage unit 30>
The carriage unit 30 is for moving (also referred to as “scanning”) the carriage 31 to which the head unit 40 is attached in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor) (FIGS. 2A and 2B).

  The carriage 31 can reciprocate in the moving direction and is driven by a carriage motor 32. The operation of the carriage motor 32 is controlled by a controller 60 on the printer side. Further, the carriage 31 detachably holds an ink cartridge that stores ink.

<Head unit 40>
The head unit 40 is for ejecting ink onto the paper S. The head unit 40 includes a head 41 having a plurality of nozzles and a head controller HC. The head 41 is provided on the carriage 31, and when the carriage 31 moves in the movement direction, the head 41 also moves in the movement direction. Then, when the head 41 is intermittently ejected while moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the medium.

  FIG. 3 is a cross-sectional view showing the structure of the head 41. The head 41 includes a case 411, a flow path unit 412, and a piezoelectric element group. The case 411 houses the piezoelectric element group, and the flow path unit 412 is joined to the lower surface of the case 411. The flow path unit 412 includes a flow path forming plate 412a, an elastic plate 412b, and a nozzle plate 412c. The flow path forming plate 412a is formed with a groove portion serving as a pressure chamber 412d, a through hole serving as a nozzle communication port 412e, a through port serving as a common ink chamber 412f, and a groove portion serving as an ink supply path 412g. The elastic plate 412b has an island portion 412h to which the tip of the piezo element PZT is joined. An elastic region is formed by an elastic film 412i around the island portion 412h. The ink stored in the ink cartridge is supplied to the pressure chamber 412d corresponding to each nozzle Nz via the common ink chamber 412f. The nozzle plate 412c is a plate on which the nozzles Nz are formed. On the nozzle surface, a yellow nozzle row Y that discharges yellow ink, a magenta nozzle row M that discharges magenta ink, a cyan nozzle row C that discharges cyan ink, and a black nozzle row K that discharges black ink (all of them) (Not shown). Each nozzle row is configured by arranging a plurality of nozzles Nz at predetermined intervals in the transport direction.

  The piezo element group includes a plurality of comb-like piezo elements PZT (drive elements), and is provided in a number corresponding to the nozzles Nz. When a drive signal COM that is a voltage waveform signal is applied to the piezo element PZT by a wiring board (hereinafter also referred to as a head board Base_H) on which the head control unit HC and the like are mounted, The piezo element PZT expands and contracts (drives) in the vertical direction according to the potential difference. When the piezo element PZT expands and contracts, the island portion 412h is pushed toward the pressure chamber 412d or pulled in the opposite direction. At this time, the elastic film 412i around the island portion 412h is deformed, and the pressure in the pressure chamber 412d rises and falls, thereby ejecting ink droplets from the nozzles.

  The head controller HC is a control IC for controlling the driving of the piezo element group PZT, and is provided on the head substrate Base_H fixed to the head 41. Details of the head controller HC will be described later.

<Detector group 50>
The detector group 50 is for monitoring the status of the printer 1. The detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, an optical sensor 54, and the like (FIGS. 2A and 2B).

  The linear encoder 51 detects the position of the carriage 31 in the moving direction. The rotary encoder 52 detects the rotation amount of the transport roller 23. The paper detection sensor 53 detects the position of the leading edge of the medium (paper S) being fed. The optical sensor 54 detects the presence / absence of the medium at the opposing position by the light emitting unit and the light receiving unit attached to the carriage 31, for example, detects the position of the edge of the paper while moving, and detects the width of the paper can do. The optical sensor 54 also detects the front end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. it can.

<Controller 60>
The controller 60 is a control unit (control unit) for controlling the printer 1. The controller 60 includes an interface unit 61 and an SOC (System-on-a-chip), and is mounted on a main board Base_M fixed to the main body of the printer 1.

  The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1.

  The SOC is a chip in which a CPU 62, a memory 63, a unit control circuit 64, and an analog voltage signal generation circuit 65 are integrally formed (FIG. 1).

  The CPU 62 is an arithmetic processing device 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 or an EEPROM. The memory 63 is also a storage unit that stores a value obtained by measuring a voltage of an analog voltage signal COM ′ described later. The CPU 62 controls each unit such as the transport unit 20 and the carriage unit 30 via the unit control circuit 64 in accordance with a program stored in the memory 63.

  Further, the CPU 62 generates a digital signal that defines the waveform shape of the drive signal COM and outputs the digital signal to the analog voltage signal generation circuit 65 in the SOC. This digital signal is called a DAC value and corresponds to waveform information for determining the waveform of the drive signal COM. That is, the CPU 62 corresponds to a digital signal generation unit that generates a digital signal (DAC value).

  Further, the CPU 62 generates various control signals such as a latch signal LAT, a change signal CH, and a transfer clock signal SCK, and outputs them to the head unit 40. These control signals are used when the head controller HC generates an SW signal for controlling application of the drive signal COM to the piezo element PZT together with the pixel data SI.

  The analog voltage signal generation circuit 65 generates an analog voltage signal COM ′, which is a voltage change pattern that is a basis of the drive signal COM, based on a digital signal (DAC value) input from the CPU 62. That is, the analog voltage signal generation circuit 65 is an analog voltage signal generation unit. For example, for a digital signal (DAC value), an analog voltage signal having a waveform corresponding to the value of the digital signal is set so that the higher the value of the digital signal, the higher the voltage, and the lower the digital signal value, the lower the voltage. Generate. In the present embodiment, the analog voltage signal COM ′ is a voltage waveform signal having a voltage of about 3.3V.

  The analog voltage signal COM ′ generated by the analog voltage signal generation circuit 65 is transmitted to the head unit 40 via a transmission unit 70 which will be described later, and power is amplified to generate the drive signal COM. A method for generating the drive signal COM will be described later.

  As described above, in this embodiment, since the CPU 62 and the analog voltage signal generation circuit 65 are integrally formed in the SOC, an accurate analog voltage signal COM ′ can be generated.

For example, when the CPU 62 and the analog voltage signal generation circuit 65 are installed as separate units, the digital signal (DAC value) generated by the CPU 62 is transmitted to the analog voltage signal generation circuit 65. There is a risk of being affected by noise or the like in the transmission path. On the other hand, in this embodiment, since the CPU 62 and the analog voltage signal generation circuit 65 are integrated, the possibility of being affected by noise in the transmission path is very small. Accordingly, the controller 60 can accurately generate the analog voltage signal COM ′ and can easily generate the drive signal COM having an accurate waveform shape. However, noise received between the CPU 62 and the analog voltage signal generation circuit 65 The CPU 62 and the analog voltage signal generation circuit 65 may be provided as separate units as long as the influence of the above does not cause a problem in the generation of the drive signal COM.

<Transmitter 70>
The transmission unit 70 includes a plurality of transmission lines that connect the main board Base_M of the controller 60 and the head board Base_H of the head unit 40. Various control signals such as the analog voltage signal COM ′ output from the SOC, the pixel data SI, the latch signal LAT, the change signal CH, and the transfer clock signal SCK are transmitted through the transmission lines of the transmission unit 70 to the head unit 40 side. Is transmitted. In this embodiment, a flexible flat cable (hereinafter also referred to as FFC) as shown in FIG. The FFC is a ribbon-shaped transmission member in which a plurality of flat transmission lines can be integrally moved while reducing the thickness of the cable itself by arranging a plurality of flat transmission lines in parallel.

  The FFC also includes a transmission line for supplying power to the head unit 40 from a power supply (for example, main power supply Vdd), a ground line for applying a ground (GND) voltage, and the like.

<About the head controller HC>
The configuration and operation of the head controller HC will be described. FIG. 4 is a diagram illustrating the configuration and operation of the head controller HC.

  The head controller HC includes a head control circuit 42 and a drive signal generation circuit 43, and is provided on a head substrate Base_H fixed to the head 41 (FIG. 4). The drive signal generation circuit 43 includes a voltage amplification unit 431, a switch 432, and a current amplification unit 433. Although only two piezo elements PZT are illustrated in FIG. 4, the printer 1 actually includes a large number of piezo elements. In the configuration shown in FIG. 4, the switch 432 and the current amplifying unit 433 are provided for each piezo element PZT.

  The head control circuit 42 outputs various control signals such as a transfer clock signal SCK, a latch signal LAT, and a change signal CH transmitted from the controller 60, and an SW signal for controlling the switch 432 according to the pixel data SI. To do.

  The drive signal generation circuit 43 power-amplifies the analog voltage signal COM ′ transmitted from the SOC of the controller 60 via the FFC, generates a drive signal COM that is a voltage waveform signal, and applies it to the piezo element PZT to apply it. The piezo element PZT is driven. That is, the drive signal generation circuit 43 corresponds to a voltage waveform signal generation unit.

  The voltage amplification unit 431 amplifies the voltage of the analog voltage signal COM ′. For example, the 3.3 V analog voltage signal COM ′ is amplified to about 40 V, which is a voltage necessary for driving each piezo element PZT. As the voltage amplifier 431, a general voltage amplifier circuit using an operational amplifier or the like can be used.

  The switch 432 inputs the analog voltage signal COM ′ voltage-amplified by the voltage amplifier 431 to the current amplifier 433 in accordance with the SW signal input from the head control circuit 42. For example, when the SW signal is at the H level, the switch 432 is turned on, and the analog voltage signal COM ′ is input to the current amplifying unit 433. On the other hand, when the SW signal is at the L level, the switch 432 is turned off, and the analog voltage signal COM ′ is not input to the current amplifying unit 433.

  The current amplifying unit 433 receives an input of the voltage-amplified analog voltage signal COM ′, amplifies the current, generates a drive signal COM, and applies it to the piezo element PZT. The current amplifying unit 433 is configured by complementarily connecting an NPN transistor and a PNP transistor. The collector of the NPN transistor is connected to the main power supply Vdd, and the collector of the PNP transistor is connected to the ground (GND). In addition, the current amplifying unit 433 can be configured using an element other than a transistor.

  The arrangement of the voltage amplification unit 431, the switch 432, and the current amplification unit 433 is not limited to the example illustrated in FIG. For example, the positions of the voltage amplification unit 431 and the switch 432 may be reversed, or the positions of the switch 432 and the current amplification unit 433 may be reversed. However, it should be noted that in this case, it is necessary to appropriately change the number of voltage amplification units 431 and current amplification units 433.

<Printer operation>
The printing operation of the printer 1 will be briefly described. The controller 60 receives a print command from the computer 110 via the interface unit 61 and controls each unit to perform a paper feed process, a dot formation process, a transport process, and the like.

  The paper feed process is a process of supplying paper to be printed into the printer and positioning the paper at a print start position (also referred to as a cue position). The controller 60 rotates the paper feed roller 21 and sends the paper to be printed to the transport roller 23. Subsequently, the transport roller 23 is rotated, and the paper fed from the paper feed roller 21 is positioned at the print start position.

  The dot forming process is a process for forming dots on paper by ejecting ink intermittently from a head moving in the moving direction (scanning direction). The controller 60 moves the carriage 31 in the movement direction, and ejects ink from the head 41 based on the print data while the carriage 31 is moving. When the ejected ink droplets land on the paper, dots are formed on the paper, and a dot line composed of a plurality of dots along the moving direction is formed on the paper.

  The carrying process is a process of moving the paper relative to the head in the carrying direction. The controller 60 rotates the transport roller 23 to transport the paper in the transport direction. By this carrying process, the head 41 can form dots at positions different from the positions of the dots formed by the previous dot formation process.

  The controller 60 alternately repeats the dot formation process and the conveyance process until there is no more data to be printed, and gradually prints an image composed of dot lines on paper. When there is no more data to be printed, the paper discharge roller 25 is rotated to discharge the paper. The determination of whether or not to discharge paper may be based on a paper discharge command included in the print data.

  The same processing is repeated when printing on the next paper, and the printing operation is terminated when not printing.

=== Generation of Drive Signal COM ===
<Description of drive signal COM>
FIG. 5 is a diagram for explaining the drive signal COM. As shown in the figure, the drive signal COM is generated using a period T with the rising timing of the latch signal LAT as a unit. The period T includes sections T1 to T4 divided by the rising timing of the latch signal LAT or the change signal CH. The sections T1 to T4 include drive pulses described later. A period T that is a repetition period corresponds to a period during which the nozzle moves by one pixel. For example, when the print resolution is 720 dpi, the period T corresponds to a period for the nozzle to move 1/720 inch. Then, based on the pixel data SI, by applying the drive pulses PS1 to PS4 of each section included in the period T to the piezo element PZT, the amount of ink ejected from the nozzles is adjusted, and an image having a plurality of gradations. Is possible.

  The drive signal COM includes a first waveform section SS1 generated in the section T1 in the repetition period, a second waveform section SS2 generated in the section T2, a third waveform section SS3 generated in the section T3, and a section T4. And a fourth waveform section SS4 to be generated. Here, the first waveform section SS1 has a drive pulse PS1. The second waveform section SS2 has a drive pulse PS2, the third waveform section SS3 has a drive pulse PS3, and the fourth waveform section SS4 has a drive pulse PS4. Each drive pulse has a voltage waveform and is generated using a potential difference between the main power supply Vdd and the ground (GND).

  When the pixel data SI is [00], the first interval signal SS1 of the drive signal COM is applied to the piezo element PZT, and the piezo element PZT is driven by the drive pulse PS1. When the piezo element PZT is driven in accordance with the drive pulse PS1, pressure fluctuations such that ink is not ejected occur in the ink, and the ink meniscus (the free surface of the ink exposed at the nozzle portion) vibrates slightly.

  When the pixel data SI is [01], the third interval signal SS3 of the drive signal COM is applied to the piezo element PZT, and the piezo element PZT is driven by the drive pulse PS3. When the piezo element PZT is driven according to the drive pulse PS3, a small amount of ink is ejected, and a small dot is formed on the medium.

  When the pixel data SI is [10], the second interval signal SS2 of the drive signal COM is applied to the piezo element PZT, and the piezo element PZT is driven by the drive pulse PS2. When the piezo element PZT is driven according to the drive pulse PS2, a medium amount of ink is ejected, and a medium dot is formed on the medium.

  When the pixel data SI is [11], the second interval signal SS2 and the fourth interval signal SS4 of the drive signal COM are applied to the piezo element PZT, and the piezo element PZT is driven by the drive pulse PS2 and the drive pulse PS4. When the piezo element PZT is driven according to the drive pulse PS2 and the drive pulse PS4, a large dot is formed on the medium.

<Generation of drive signal COM>
An operation of generating the drive signal COM from the DAC value that is a digital signal in the printer 1 will be described.

  First, the overall flow will be described. As shown in FIG. 4, in this embodiment, the CPU 62 of the controller 60 generates a digital signal (DAC value) that defines the waveform shape of the drive signal COM. Based on this DAC value, the analog voltage signal generation circuit 65 generates an analog voltage signal COM ′. COM ′ is a small-amplitude voltage waveform signal that is the basis of the drive signal COM. The generated COM ′ is transmitted to the head unit 40 side via the transmission unit 70 (FFC), and the voltage amplification unit 431 performs voltage amplification. Is done. Then, current amplification is performed in the current amplification unit 433 to generate the drive signal COM.

  Next, a method for generating the analog voltage signal COM ′ from the DAC value that is a digital signal will be described.

  FIG. 6 is a diagram for explaining a part of the analog voltage signal COM ′. FIG. 6 shows the analog voltage signal COM ′ immediately after being generated by the analog voltage signal generation circuit 65, that is, before being amplified by the voltage amplifier 431. As shown in the figure, the analog voltage signal COM ′ is generated as a voltage waveform having a drive voltage Vh represented by a potential difference between the maximum voltage value Vmax and the minimum voltage value Vmin.

  First, the CPU 62 obtains an output voltage for each update period τ based on a parameter for generating the drive signal COM. Taking the drive pulse PS ′ shown in FIG. 6 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, and a time PWh1 for maintaining the intermediate voltage VC. The time PWd1 for dropping the voltage with a constant slope from the intermediate voltage VC to the minimum voltage Vmin, the time PWh2 for maintaining the minimum voltage Vmin, and the time for increasing the voltage with a constant slope from the minimum voltage Vmin to the maximum voltage Vmax There are PWc1, a time PWh3 for maintaining the maximum voltage Vmax, a time PWd2 for dropping the voltage with a constant gradient from the maximum voltage Vmax 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 maximum voltage Vmax and the minimum voltage Vmin in the drive pulse PS ′ as described above, and the minimum potential (minimum voltage Vmin of the piezo element PZT when the drive pulse PS ′ is applied. And the maximum potential (potential determined by the maximum voltage Vmax). The reference voltage Vc defines a deformation state serving as a reference in the piezo element PZT, and is, for example, 40% of the drive voltage Vh (ratio 0.4). The intermediate voltage VC is a voltage obtained by adding the reference voltage Vc to the minimum voltage Vmin. The maximum voltage Vmax is a voltage obtained by adding the drive voltage Vh to the minimum voltage Vmin. These parameters are stored in the memory 63.

  The CPU 62 determines the drive voltage Vh at a predetermined timing (for example, paper feed timing), and calculates the reference voltage Vc, the intermediate voltage VC, and the maximum voltage Vmax. 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). Based on the obtained output voltage for each update cycle τ, a DAC value for each update cycle τ is determined and stored in the work area of the memory 63.

  When generating the drive signal COM, the CPU 62 sequentially outputs the DAC value for each update period τ to the analog voltage signal generation circuit 65.

  FIG. 7 is a diagram for explaining an operation of dropping the output voltage of COM ′ generated by the analog voltage signal generation circuit 65 from the voltage V1 to the voltage V4. In the illustrated example, the DAC value [dc1] corresponding to the voltage V1 is output at the timing t (n) defined by the clock CLK. Thereby, the voltage V1 is output from the analog voltage signal generation circuit 65 in the period τ (n). Until the update period τ (n + 4), the DAC value [dc1] corresponding to the voltage V1 is sequentially output, and the voltage V1 is continuously output from the analog voltage signal generation circuit 65. Further, at the timing t (n + 5), the DAC value [dc2] corresponding to the voltage V2 is output. As a result, the output of the analog voltage signal generation circuit 65 drops from the voltage V1 to the voltage V2 in the cycle τ (n + 5). Similarly, at the timing t (n + 6), the DAC value [dc3] corresponding to the voltage V3 is output. As a result, the output of the analog voltage signal generation circuit 65 drops from the voltage V2 to the voltage V3 in the cycle τ (n + 6). Similarly, since the DAC value is output, the voltage output from the analog voltage signal generation circuit 65 gradually decreases. Then, at the period τ (n + 10), the output of the analog voltage signal generation circuit 65 drops to the voltage V4.

  The analog voltage signal COM ′ generated in this way is amplified by the voltage amplifying unit 431 so as to have a waveform having a predetermined voltage. In the present embodiment, it is assumed that the minimum voltage value of the analog voltage signal COM ′ after voltage amplification is Vmin = 1.40V, and the maximum voltage value is Vmax = 40.0V.

  In the present embodiment, the DAC value output from the CPU 62 is represented by 10-bit data (0 to 1023 in decimal). For example, when the DAC value is decimal [0] (in hexadecimal [0h], binary [0000000]), that is, when the DAC value is the minimum value, the analog voltage signal generation circuit 65 generates the DAC value. The voltage of COM ′ after voltage amplification by the voltage amplification unit 431 becomes Vmin (= 1.40 V) which is the lowest voltage. When the DAC value is decimal [1023] (hexadecimal [3FF] and binary [11111111111]), that is, when the DAC value is the maximum value, the voltage of COM ′ is the highest voltage. Vmax (= 40V). In other words, in this embodiment, the minimum voltage of COM ′ after voltage amplification output from the voltage amplification unit 431 is 1.40 V, and when the DAC value increases by one, the output voltage is about 0.038 V (= (40 -1.4) / 1024).

  However, due to the accuracy error of the analog voltage signal generation circuit 65 and the like, the actually output voltage value is not always exactly such a value.

=== First Embodiment ===
As described above, the analog voltage signal COM ′ is generated by inputting the DAC value which is a digital signal to the analog voltage signal generation circuit 65. A voltage signal having a voltage corresponding to the DAC value is generated by voltage amplification by the voltage amplification unit 431.

  However, there may be a deviation in the voltage value that is actually output due to the accuracy error of the analog voltage signal generation circuit 65, the voltage amplification unit 431, and the like. That is, when a certain value [dc] is input as the DAC value, even if the voltage value theoretically output is V (id) (hereinafter, V (id) is the theoretical value of the output voltage). ), The voltage value V (id) is not always output with respect to the input of [dc]. The fact that the actually output voltage value deviates from the theoretical value means that the amplitude of the analog voltage signal COM ′ (for example, the drive voltage Vh in FIG. 6) is output different from the intended amplitude. is there. In this case, since the waveform of the finally generated drive signal COM is also different from the intended waveform, the amount of ink ejected from the piezo element PZT cannot be accurately controlled.

  In particular, as shown in FIG. 1, when the analog voltage signal generation circuit 65 is manufactured integrally with the SOC, it is difficult to ensure the accuracy of the output voltage of the analog voltage signal generation circuit 65. Further, when the analog voltage signal COM ′ is transmitted via the FFC, the waveform of the signal is disturbed due to the influence of noise, and the voltage value actually output from the voltage amplifier 431 may deviate from the theoretical value. .

  Therefore, when a deviation occurs between the voltage value of COM ′ theoretically output with respect to the DAC input value and the voltage value of COM ′ actually output, the deviation is corrected, It is necessary to perform correction so that an accurate voltage value is output. At that time, it is desirable that correction can be performed at as low a cost as possible.

  Therefore, in the first embodiment, a correction coefficient (for example, k) for correcting the DAC value [dc] is determined for each printer, and based on a value [k × dc] obtained by multiplying the DAC value by the correction coefficient. An analog voltage signal COM ′ is generated. Thus, an accurate drive signal COM is generated so that the output voltage value is close to the theoretical value V (id) with respect to the input of the corrected DAC value [k × dc].

<Correction value setting work>
FIG. 8 is a diagram illustrating a flow of setting work for changing the DAC value in the first embodiment. In the present embodiment, in the printer manufacturing process, the optimum correction value is set for each printer by executing the processes of S101 to S103 for each printer.

  First, the voltage value of the analog voltage signal COM ′ is measured (S101). In the present embodiment, the maximum value Vmax and the minimum value Vmin of the voltage of the analog voltage signal COM ′ are measured at a point immediately after being output from the voltage amplifier 431 (point A in FIG. 4). That is, the voltage of the analog voltage signal COM ′ after the voltage amplification and before the current amplification is measured. By measuring the voltage value of this part, in addition to the output error in the analog voltage signal generation circuit 65, the influence of noise that may be received during FFC transmission, the influence of the output error in the voltage amplifier 431, etc. are collectively detected. can do. The measurement of the voltage value is performed at the timing of mounting the main board Base_M and the head board Base-H on the printer 1 in the manufacturing process of the printer 1.

  FIG. 9 is a diagram illustrating voltage measurement in the first embodiment. The waveform indicated by the broken line in FIG. 9 is an ideal voltage waveform of the analog voltage signal COM ′ output from the voltage amplifier 431 with respect to an input of a certain DAC value [dc]. That is, it represents the theoretical output voltage value V (id) when the DAC value [dc] is input. A waveform indicated by a solid line is an actual voltage waveform of the analog voltage signal COM ′ output with respect to the input of the same DAC value [dc]. That is, it represents the actual output voltage value V (m) when the DAC value [dc] is input.

  The voltage value V (m) actually output with respect to the input of the DAC value [dc] due to the output error of the analog voltage signal generation circuit 65 and the voltage amplification unit 431 is theoretically as shown in FIG. The theoretical value V (id) of the output voltage is shifted. For example, in FIG. 9, when dc = [0] (decimal number display) is input as the DAC value, the theoretical value of the voltage output from the voltage amplifier 431 is the minimum voltage value Vmin (id) = 1.40V. It is. However, actually, a smaller value Vmin (m) = 1.20V is output. Similarly, when dc = [1023] (decimal number display) is input as the DAC value, the theoretical value of the voltage output from the voltage amplifying unit 431 is the maximum voltage value Vmax (id) = 40.0V. However, actually, a value Vmax (m) = 41.0 V larger than that is output.

  In the present embodiment, the maximum value Vmax (m) (= 41.0 V) of the voltage of the analog voltage signal COM ′ that is actually output and the minimum value Vmin (m) (= 1.20 V) of the actual output voltage. ) Is measured.

ここで、ΔＶ（ｉｄ）は理論上の電圧の最高値のＶmax（ｉｄ）と、理論上の電圧の最低値Ｖmin（ｉｄ）との電位差である。つまり、電圧波形ＣＯＭ´の理論上の振幅を表し、図９においては、ΔＶ（ｉｄ）＝３８．６Ｖ（＝４０.０−１．４０）である。 After the maximum value Vmax (m) and the minimum value Vmin (m) of the output voltage are measured, the correction value k is calculated based on the measured value (S102). The correction value k is calculated by the following formula 1.

Here, ΔV (id) is a potential difference between the maximum value Vmax (id) of the theoretical voltage and the minimum value Vmin (id) of the theoretical voltage. That is, it represents the theoretical amplitude of the voltage waveform COM ′, and in FIG. 9, ΔV (id) = 38.6V (= 40.0−1.40).

  The correction value k calculated by the equation (1) includes the theoretical amplitude ΔV (id) of the voltage waveform output with respect to the input of the DAC value [dc], and the amplitude (Vmax) of the actually output voltage waveform. (M) -Vmin (m)). That is, it represents the degree of deviation from the theoretical value of the voltage value that is actually output with respect to the input DAC value. In the case of FIG. 9, k = 38.6 / (41.0−1.20) = 0.97 is calculated, and the theoretical amplitude of COM ′ is 0.97 times the amplitude that is actually output. It shows that there is.

  Thereafter, the correction value k, which is a value obtained by measuring the voltage of the analog voltage signal COM ′, is stored in the memory 63 that is a storage unit (S103). Thereby, the correction value k is set for each printer. Since only voltage measurement at two points is performed in the printer manufacturing stage, it is not necessary to perform waveform adjustment work or the like for each printer, so that the manufacturing cost can be reduced.

<Correction action>
The printer having the correction value k stored in the memory 63 is shipped from the manufacturing factory, and when printing is performed under the user who purchased the printer, the correction of the DAC value [dc] is performed using the stored correction value k. By performing this, printing is executed while generating an accurate drive signal COM.

  Specifically, when the CPU 62 generates the DAC value [dc], the DAC value [dc] is set such that [dc ′] = dc × k by multiplying the correction coefficient k stored in the memory 63. Change (correct). Then, when the newly generated corrected DAC value [dc ′] is input to the analog voltage signal generation circuit 65, the analog voltage signal COM ′ is generated based on the corrected DAC value [dc ′]. The COM ′ is voltage amplified in the voltage amplifying unit 431.

  For example, in the case of FIG. 9, when the DAC value [dc] before correction is input to the analog voltage signal generation circuit 65, the amplitude (Vmax (m) −Vmin () larger than the theoretical amplitude ΔV (id) = 38.6V. m)) = 39.8V is output from the voltage amplifier 431. However, by inputting the DAC value [dc ′] after the correction value, a waveform having an amplitude that is smaller by a ratio obtained by multiplying the correction value k is output. As described with reference to FIG. 6, the analog voltage signal generation circuit 65 outputs a signal having a voltage corresponding to the input DAC value, and therefore, based on the corrected DAC value [dc ′]. The amplitude of the output waveform is close to the theoretical amplitude ΔV (id).

  As a result, the finally generated drive signal COM becomes a voltage waveform signal close to the original ideal value, so that the drive of the piezo element PZT can be accurately controlled.

<Summary of First Embodiment>
In the printer of the first embodiment, the analog voltage signal generation circuit 65 of the controller 60 generates the analog voltage signal COM ′ based on the DAC value (digital signal) that defines the waveform shape. The generated COM ′ is transmitted from the controller 60 to the head unit 40 via the FFC. Thereafter, COM ′ is voltage-amplified by the voltage amplifying unit 431 of the head unit 40, and then the current is amplified by the current amplifying unit 433, thereby generating the drive signal COM. By applying this drive signal COM, the piezo element PZT is driven (vibrated) to eject ink from the nozzles.

  In order to generate an accurate drive signal COM, it is necessary to output an analog voltage signal COM ′ with little deviation. First, the maximum value Vmax (m) and the minimum value Vmin (m) of the voltage of the analog voltage signal COM ′ after the voltage amplification in the voltage amplification unit 431 and before the current amplification in the current amplification unit 433 are performed. taking measurement. Then, a correction value k calculated based on the relationship between the actually measured voltage potential difference (Vmax (m) −Vmin (m)) and the theoretical potential difference ΔVid is stored in the memory 63. At the time of printing, by changing (correcting) the DAC value using the correction value k stored in the memory 63, the output voltage value of the generated analog voltage signal COM ′ becomes close to the theoretical value. Like that. As a result, an accurate drive signal COM can be generated while reducing costs.

=== Second Embodiment ===
According to the method of the first embodiment, it is possible to generate the drive signal COM having a waveform close to an ideal amplitude. However, the waveform input to the head control unit HC is required to have a voltage value within a predetermined range in addition to being accurate in shape. For example, when the analog voltage signal COM ′ is generated in a range that deviates from between Vdd and GND in FIG. 9, each circuit of the head control unit HC (for example, the switch 432 and the current amplification unit 433) operates normally. You may not be able to.

  Therefore, in the second embodiment, a drive signal COM having an accurate waveform and included in an appropriate voltage range is generated. Specifically, the DAC value is changed by calculating the optimum DAC input value by calculating backward from the voltage value to be output from the voltage amplifier 431. The printer configuration itself is the same as that of the first embodiment.

<Setting Operation of Second Embodiment>
FIG. 10 is a diagram illustrating a flow of setting work for changing the DAC value in the second embodiment. In the second embodiment, in the printer manufacturing process, each process of S201 to S202 is executed for each printer, and a value used to generate an optimum DAC value for each printer is set.

  First, the voltage value of the analog voltage signal COM ′ is measured as in the first embodiment (S201). The voltage value is measured immediately after being output from the voltage amplification unit 431 and before being amplified by the current amplification unit 433 (point A in FIG. 4).

  FIG. 11 is a diagram for explaining voltage measurement in the second embodiment. In the second embodiment, the maximum value Vmax (m) and the minimum value Vmin (m) of the voltage of the analog voltage signal COM ′ are measured. These values are exactly the same as the maximum voltage value Vmax (m) and the minimum voltage value Vmin (m) in FIG. The maximum value Vmax (m) and the minimum value Vmin (m) of the actually measured voltage are stored in the memory 63 (S201), and then the printer is shipped.

<Correction action>
In the second embodiment, the maximum value Vmax (m) and the minimum value Vmin (m) of the voltage stored in the memory 63 are used, and the magnitude of the input DAC value and the analog generated based on the DAC value. The relationship with the magnitude of the voltage of the voltage signal COM ′ is obtained. Then, based on the relationship, the CPU 62 back-calculates the DAC value [dc] to be input in order to output an arbitrary voltage value V (dc) (referred to as a target voltage value), and calculates the value of [dc]. Change (correct).

ここで、ＮはＤＡＣ値として入力するデータのビット数を表す。本実施形態におけるＤＡＣ値は１０ビット（１０進数で０〜１０２３）のデータであることからＮ＝１０２４となる。 The relationship between the input DAC value [dc] and the target voltage value V (dc) output based on the DAC value [dc] is expressed by the following Expression 2.

Here, N represents the number of bits of data input as a DAC value. Since the DAC value in this embodiment is 10-bit data (0 to 1023 in decimal), N = 1024.

  The part of (Vmax (m) −Vmin (m)) / N in Equation 2 indicates the voltage increase rate per DAC value. For example, in this embodiment, the voltage output when dc = [1023] (decimal number display) is input as the DAC value is Vmax (m) = 41.0 V, and dc = [0] (10 Since the voltage output when the input (in decimal notation) is Vmin (m) = 1.20 V, the voltage increase rate per DAC value is (41.0-1.20) /1024=0.039. . That is, every time the input DAC value increases by 1 in decimal, the output voltage increases by about 0.039V.

  By multiplying (Vmax (m) −Vmin (m)) / N by the DAC value [dc], a voltage value corresponding to an increase when the DAC value [dc] is input is calculated. Then, the target voltage value V (dc) is calculated by adding the minimum voltage value Vmin (m) to the calculated voltage value (see FIG. 11).

Here, when Expression 2 is modified, an expression for obtaining a DAC value [dc] necessary to output an arbitrary voltage value V (dc) (target voltage value) is obtained as in Expression 2 ′ below.

  From the target voltage value V (dc) to be output and the Vmax (m) and Vmin (m) stored in the memory 63, the DAC value [dc] to be input can be calculated backward using the equation 2 ′. At the time of printing, the controller 60 inputs the DAC value [dc] calculated by the equation 2 ′ to the analog voltage signal generation circuit 65, whereby the analog voltage signal COM ′ (voltage amplification) having a desired voltage value V (dc) is obtained. Can be output from the voltage amplifier 431 with high accuracy.

  For example, the DAC value [dc] for outputting a voltage of V (dc) = 20V is dc = (20−1.2) × 1024 / (40−1.2) = 496 from Equation 2 ′. Calculated. Therefore, if [496] (decimal number display) is input to the analog voltage signal generation circuit 65 as the DAC value, the analog voltage signal COM ′ having a voltage of 20 V, which is the target voltage value, is output at the output terminal of the voltage amplifier 431. Is output. As a result, an accurate drive signal COM is generated, and the piezoelectric element can also be controlled accurately.

  Further, the analog voltage signal COM ′ after voltage amplification in the present embodiment has a minimum voltage value of Vmin (m), and the voltage value of COM ′ is clearly determined by using the minimum voltage value as a reference. That is, the output voltage value is clearly determined with respect to the input DAC value. Therefore, the voltage value of the generated COM ′ can be adjusted by controlling the input DAC value.

  Thus, the voltage of the analog voltage signal COM ′ generated based on the changed DAC value can be adjusted so as to be larger than the GND voltage and smaller than the Vdd voltage. For example, even if the actually measured minimum voltage value Vmin (m) is lower than the GND voltage, the CPU 62 ensures that the output COM ′ voltage is always greater than the GND voltage. Adjust the DAC value. As a result, the analog voltage signal COM ′ having a voltage larger than the GND voltage can be reliably output.

  That is, in the present embodiment, since the drive signal COM can be generated with a voltage within a range in which each circuit of the head control unit HC can properly operate, the possibility of malfunction in the head control unit HC is very small. Become.

<Summary of Second Embodiment>
Also in the second embodiment, an accurate drive signal COM is generated by changing the DAC value using a value obtained by measuring the voltage of the analog voltage signal COM ′.

  First, the maximum value Vmax (m) and the minimum value Vmin (m) of the voltage of the analog voltage signal COM ′ after the voltage amplification in the voltage amplification unit 431 and before the current amplification in the current amplification unit 433 are performed. taking measurement. Then, the measured voltage value is stored in the memory 63. At the time of printing, the CPU 62 calculates, from the voltage value stored in the memory 63, Equation 2 representing the relationship between the magnitude of the input DAC value and the voltage magnitude of the analog voltage signal COM ′ generated based on the DAC value. Ask. Based on Equation 2, the DAC value [dc] to be input in order to output the target voltage value V (dc) is calculated backward. When the input DAC value is changed (corrected) based on the back-calculated value, the voltage of the analog voltage signal COM ′ is output as the target voltage value V (dc), so that a signal having an arbitrary voltage value is generated with high accuracy. can do.

  Further, since the relationship between the input DAC value and the output voltage value is clarified, the voltage range of the generated analog voltage signal COM ′ can be reliably set to the main power supply Vdd by appropriately setting the DAC value. The voltage can be smaller than the voltage of the ground (GND). Thereby, only a signal having a voltage in a range in which each circuit of the head control unit HC can operate normally is generated, and malfunctions in the head control unit HC can be suppressed.

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

<About liquid ejection device>
In each of the above-described embodiments, a printer has been described as an example of a liquid ejection device that reduces heat generation, but 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 molding machine, liquid vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to this embodiment to the various liquid ejection apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus.

<About piezo elements>
In each of the above-described embodiments, the piezo element PZT is exemplified as the element that performs the operation for ejecting the liquid. However, other elements may be used. For example, a heating element or an electrostatic actuator may be used.

<Regarding Transistor of Current Amplifier 433>
In each of the above-described embodiments, the NPN transistor and the PNP transistor are exemplified as the transistors included in the current amplification unit 433. However, other types of transistors may be used as long as they can amplify current for the analog voltage signal COM ′.

<About other devices>
In each of the above-described embodiments, an ink jet printer (serial printer) of a type that moves the head 41 together with the carriage has been described as an example. However, the printer may be a so-called line printer having a fixed head.

1 Printer 20 transport unit, 21 paper feed roller, 22 transport motor,
23 transport roller, 24 platen, 25 discharge roller,
30 Carriage unit, 31 Carriage, 32 Carriage motor,
40 head units, 41 heads, 411 case, 412 flow path unit,
412a flow path forming plate, 412b elastic plate, 412c nozzle plate,
412d pressure chamber, 412e nozzle communication port, 412f common ink chamber,
412g Ink supply path, 412h island part, 412i elastic film,
42 head control circuit, 43 drive signal generation circuit,
431 Voltage amplifier, 432 switch, 433 Current amplifier,
50 detector groups, 51 linear encoder, 52 rotary encoder,
53 Paper detection sensor, 54 Optical sensor,
60 controller, 61 interface part,
62 CPU, 63 memory, 64 unit control circuit,
65 analog voltage signal generation circuit, 70 transmission unit,
110 computers,
SOC System-on-a-tip,
PZT Piezo element

Claims (6)

(A) a control unit that generates an analog voltage signal based on a digital signal that defines the waveform shape of the signal;
(B) a voltage amplifier for amplifying the analog voltage signal;
A current amplifying unit that amplifies the voltage amplified analog voltage signal to generate a drive signal; and
A plurality of elements driven by the drive signal to eject liquid from the nozzle;
Have a, a head portion of the current amplifier is provided in each of said plurality of elements,
(C) a transmission unit that transmits the analog voltage signal from the control unit to the head unit;
(D) a storage unit for storing a value obtained by measuring the voltage of the analog voltage signal after voltage amplification and before current amplification;
A liquid ejection device comprising:
The control unit changes the digital signal using the value stored in the storage unit, and generates the analog voltage signal based on the digital signal. The liquid ejection device according to claim 1,
The storage unit
The highest and lowest actually measured voltages of the analog voltage signal after voltage amplification and before current amplification;
The maximum and minimum theoretical voltages of the analog voltage signal after voltage amplification and before current amplification;
The correction value calculated based on the relationship is stored,
The liquid ejecting apparatus according to claim 1, wherein the control unit changes the digital signal by multiplying the digital signal by the correction value. The liquid ejection device according to claim 1,
The storage unit stores the highest value and the lowest value of the actually measured voltage of the analog voltage signal after voltage amplification and before current amplification,
The control unit obtains a relationship between the magnitude of the digital signal and the magnitude of the voltage of the analog voltage signal generated based on the digital signal from the stored maximum and minimum values of the voltage, and the relationship And changing the digital signal based on the above. The liquid ejection device according to claim 3,
The liquid ejecting apparatus, wherein a voltage of the analog voltage signal generated based on the changed digital signal is larger than a ground voltage. The liquid ejection device according to claim 1,
The controller is
A liquid ejecting apparatus comprising: a chip in which the digital signal generating unit that generates the digital signal and the analog voltage signal generating unit that generates the analog voltage signal are integrally formed. In the control unit, generating an analog voltage signal based on a digital signal that defines the waveform shape of the signal;
Transmitting the analog voltage signal from the control unit to the head unit;
In the head part, amplifying the analog voltage signal;
Amplifying the analog voltage signal that has been voltage amplified by a current amplifying unit provided in each of a plurality of elements that eject liquid from a nozzle to generate a drive signal;
And that by driving the plurality of elements by said drive signal, thereby ejecting liquid from the nozzle,
Storing the value obtained by measuring the voltage of the analog voltage signal after voltage amplification and before current amplification in the storage unit;
Changing the digital signal using the value stored in the storage unit, and generating the analog voltage signal based on the digital signal;
A liquid jetting method.

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