JP2012206284A - Device and method for ejection of liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate an accurate drive signal that is strong in disturbance in a liquid ejection device.SOLUTION: A liquid ejection device includes: (A) a control part that generates an analog voltage signal based on the digital signal that defines the waveform shape of the signal; (B) a head part which includes a voltage waveform signal generation part that amplifies the voltage and amplifies the current of the analog voltage signal and generates the voltage waveform signal and an element that jets the liquid from a nozzle and that is driven according to the potential difference of the voltage waveform signal and the ground; and (C) a transmission part that transmits the analog voltage signal from the control part to the head part. The transmission part has: a twisted-pair cable in which a transmission line that transmits the analog voltage signal and a ground line are twisted; or a coaxial cable in which the transmission line is enclosed concentrically by the ground line.

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 signal to an element such as a piezoelectric element provided inside the head unit and vibrating the piezoelectric element is known. Yes.

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 for generating a drive signal by amplification has been proposed. (For example, patent document 1).

JP 2000-343690 A

If a sufficiently large capacitor for power supply is provided on the head by the method of Patent Document 1, it is not necessary to flow a current having a large peak that flows instantaneously when driving the head through a cable such as an FFC. That is, since an average current flows through a cable such as an FFC, heat generation in the cable can be reduced, and the number of FFC cores can be reduced. However, when a voltage waveform signal having a small amplitude is transmitted from the control unit to the head unit, distortion or the like occurs in the voltage waveform signal due to the influence of disturbance such as noise in the transmission path (FFC). The drive signal may not be generated. In such a case, the liquid ejection amount cannot be controlled with high accuracy.

An object of the present invention is to generate an accurate drive signal that is resistant to disturbances in a liquid ejecting apparatus.

The main invention for achieving the above object is as follows: (A) a controller that generates an analog voltage signal based on a digital signal that defines the waveform shape of the signal; and (B) voltage amplification and current amplification of the analog voltage signal. (C) the analog voltage, and a head portion having a voltage waveform signal generating unit that generates a voltage waveform signal, and an element that is driven according to a potential difference between the voltage waveform signal and the ground and that ejects liquid from a nozzle. A transmission unit for transmitting a signal from the control unit to the head unit, wherein a twisted pair cable in which a transmission line for transmitting the analog voltage signal and a ground line are twisted, or a transmission line for transmitting the analog voltage signal And a transmission unit having a coaxial cable in which ground wires are concentrically surrounded.

  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 which shows an example of arrangement | positioning of the transmission line in FFC in a comparative example. It is the schematic of a twisted pair cable. It is the schematic of a coaxial cable. It is the schematic of the transmission part 70 in 2nd Embodiment. It is the schematic of the transmission part 70 in 3rd 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; and (B) a voltage waveform signal generation that generates a voltage waveform signal by performing voltage amplification and current amplification on the analog voltage signal. And a head unit that is driven in accordance with a potential difference between the voltage waveform signal and the ground and ejects liquid from a nozzle, and (C) the analog voltage signal is transmitted from the control unit to the head unit. A transmission unit for transmitting, a twisted pair cable in which a transmission line for transmitting the analog voltage signal and a ground line are twisted together, or a coaxial cable in which a ground line is concentrically surrounded by a transmission line for transmitting the analog voltage signal A liquid ejection device comprising: a transmission unit having the same.
According to such a liquid ejection device, it is possible to generate an accurate drive signal that is resistant to disturbance.

In this liquid ejecting apparatus, the transmission unit includes a plurality of transmission lines for transmitting signals, and a part of one transmission line and a part of another transmission line are joined to each other among the plurality of transmission lines. It is desirable.
According to such a liquid ejecting apparatus, even when the transmission unit has a plurality of transmission lines, it is possible to suppress tangling of the transmission lines during the liquid ejecting operation. This prevents the operation of the head that ejects the liquid from interfering.

In such a liquid ejection device, it is preferable that the transmission unit includes a flexible flat cable in which a plurality of flat transmission lines are arranged in parallel.
According to such a liquid ejection device, it becomes easier to suppress the tangling of the transmission lines. In addition, since the number of parts constituting the transmission unit is reduced, the manufacturing cost can be reduced,
Maintenance is also easy.

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, an analog voltage signal is generated based on a digital signal that defines the waveform shape of the signal, and a twisted pair cable in which a transmission line and a ground line for transmitting the analog voltage signal are twisted, or the analog voltage signal is Transmitting the analog voltage signal to the head unit via a coaxial cable in which a ground line is concentrically surrounded by a transmission line for transmission; and in the voltage waveform signal generation unit provided in the head unit, the analog voltage signal is A liquid ejection method is disclosed that includes generating a voltage waveform signal by voltage amplification and current amplification, and ejecting liquid from a nozzle by driving an element according to a potential difference between the voltage waveform signal and the ground. It becomes.

=== 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. Printer 1 is paper, cloth,
A liquid ejecting apparatus that records (prints) characters and images on a medium such as a film, and is communicably connected to a computer 110 that is an external apparatus.

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 a medium (
For example, data (for example, gradation values) relating to dots formed on paper S or the like. 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, data corresponding to no dot [00]
Data [01] corresponding to small dots, data [10] corresponding to formation of medium dots, and data [11] corresponding to large dots.

The printer 1 includes a transport unit 20, a carriage unit 30, and a head unit 4.
0, 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 bird's-eye view showing the configuration of the printer 1 of this embodiment, and FIG. 2B is a side view showing the configuration of the printer 1.

The transport unit 20 feeds a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction).
It is for making it convey. Here, the transport direction is a direction that intersects the moving direction of the carriage. 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. Head unit 4
0 includes a head 41 having a plurality of nozzles and a head controller HC. This 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. Case 411 houses a piezo element group,
A 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 passes through the common ink chamber 412f to each nozzle N.
The pressure chamber 412d corresponding to z is supplied. The nozzle plate 412c is a plate on which the nozzles Nz are formed. On the nozzle face, a yellow nozzle row Y for ejecting yellow ink, a magenta nozzle row M for ejecting magenta ink, a cyan nozzle row C for ejecting cyan ink, and a black nozzle row K for ejecting black ink are formed. Has been. 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. A wiring board on which the head controller HC and the like are mounted (hereinafter,
When a drive signal COM, which is a voltage waveform signal, is applied to the piezo element PZT by the head substrate Base_H), the piezo element PZT expands and contracts (drives) in the vertical direction according to the potential difference between the drive signal COM and the ground. . 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.
It 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. Further, the optical sensor 54
Depending on the situation, the front end (the end on the downstream side in the transport direction, also referred to as the upper end), the rear end (
It is also possible to detect an end portion on the upstream side in the transport direction and also referred to as a lower end).

<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 includes a storage element such as a RAM or an EEPROM. 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.

In addition, the CPU 62 generates a digital signal that defines the waveform shape of the drive signal COM, and performs SO processing.
The signal is output to the analog voltage signal generation circuit 65 in C. This digital signal is called a DAC value and corresponds to waveform information for determining the waveform of the drive signal COM. That is, CPU 6
2 corresponds to a digital signal generation unit that generates a digital signal (DAC value).

Further, the CPU 62 latches the latch signal LAT, the change signal CH, and the transfer clock signal SC.
Various control signals such as K are generated and output to the head unit 40. These control signals are used when generating a SW signal for controlling application of the drive signal COM to the piezo element PZT together with the pixel data SI described above in the head controller HC described later.

The analog voltage signal generation circuit 65 is based on a digital signal (DAC value) input from the CPU 62 and is an analog voltage signal CO that is a voltage change pattern that is a basis of the drive signal COM.
M ′ is generated. 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 described later, and a drive signal COM is generated by voltage amplification and current amplification. A method for generating the drive signal COM will be described later.

As described above, in this embodiment, the CPU 62 and the analog voltage signal generation circuit 65 are connected to the SO.
Since it is integrally formed in C, 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 the main board Base_M of the controller 60 and the head unit 40.
The plurality of transmission lines connecting the head substrate Base_H. 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. The transmission unit 70 has a power source (for example, the main power source Vdd).
) Includes a transmission line for supplying power to the head unit 40, a ground line for applying a ground (GND) voltage, and the like. The potential difference between the main power supply Vdd and the ground is 4
It is about 2V.

In the present embodiment, various cables are used as the transmission line of the transmission unit 70. Transmission unit 7
Details of 0 will be described later.

<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 case of the configuration shown in FIG. 4, the switch 432 and the current amplifier 43
3 is provided for each piezo element PZT.

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

The drive signal generation circuit 43 performs voltage amplification and current amplification on the analog voltage signal COM ′ transmitted from the SOC of the controller 60 via the transmission unit 70 to generate a drive signal COM that is a voltage waveform signal, and the piezo element PZT. To drive the piezo element PZT. That is, the drive signal generation circuit 43 corresponds to a voltage waveform signal generation unit.

The voltage amplifier 431 amplifies the voltage of the analog voltage signal COM ′ to generate an analog voltage signal COM ″. For example, an analog voltage signal COM ′ of 3.3 V is amplified to about 30 V that 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 ″ generated 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 CO
M ″ is input to the current amplification unit 433. On the other hand, when the SW signal is at the L level, the switch 4
32 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 analog voltage signal COM ″, amplifies the current to generate a driving signal COM, and applies the driving signal COM to the piezo element PZT. The current amplifying unit 433 is NPN
A type transistor and a PNP type transistor are complementarily connected.
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). It is also possible to configure the current amplifying unit 433 using an element other than a transistor such as a MOS / FET.

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.

Further, the head substrate Base_H has a capacitor (not shown) having a sufficient capacity, and Vd
Even if a large current flows through many piezo elements PZT at the same time, a current is instantaneously supplied from the capacitor and a large current does not flow through the transmission unit 70. Can be reduced.

Next, FIG. 5 shows 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 a section T1 in a repetition cycle,
A second waveform section SS2 generated in the section T2, a third waveform section SS3 generated in the section T3,
And a fourth waveform section SS4 generated in the section T4. Here, the first waveform section SS1 has a drive pulse PS1. Further, the second waveform section SS2 outputs the drive pulse PS2 to the third waveform section S.
S3 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 an 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.

<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,
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 has a carriage 3
1 is moved in the moving direction, and ink is ejected 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.

=== Embodiment ===
In the present embodiment, among the plurality of transmission lines included in the transmission unit 70, the analog voltage signal COM
The transmission line for transmitting 'and the ground (GND) line are adjacent to each other. When the analog voltage signal COM ′ is transmitted from the controller 60 to the head unit 40,
An accurate drive signal COM is generated by making it less susceptible to disturbances such as noise.

<Comparative example>
First, as a comparative example, a case where the analog voltage signal COM ′ and the ground line (GND) are arranged at separate positions will be described. In the comparative example, a flexible flat cable (hereinafter also referred to as FFC) is used as the transmission unit 70. The FFC is a transmission member in which a plurality of flat transmission lines can be moved integrally while reducing the thickness of the cable itself by arranging a plurality of flat transmission lines in parallel.

FIG. 6 is a diagram illustrating an example of the arrangement of transmission lines in the FFC in the comparative example. This figure is a diagram schematically showing a cross section of the FFC in order to explain the arrangement of transmission lines (arrangement of various signals).
The rectangles numbered and arranged in the FFC represent flat transmission lines. Note that FIG. 6 does not explain all signals actually transmitted.

In the comparative example, the FFC is a flexible flat cable in which 12 flat transmission lines are arranged in parallel. The transmission lines represented by the first to second and tenth to twelfth hatched portions from the upper side of FIG. 6 represent the ground line (GND), and the seventh transmission line colored black transmits the analog voltage signal COM ′. Represents a line. The third to sixth lines represent transmission lines for various control signals, the eighth represents the transmission line for the main power supply Vdd, and the ninth represents the transmission line for the control logic power supply.

When various signals are transmitted from the controller 60 to the head unit 40 via the transmission line in the FFC, the signals may be affected by noise. In particular, since COM ′ is an analog signal, the voltage waveform is distorted or disturbed when affected by noise. When disturbance or the like occurs in the waveform of COM ′, the waveform of the drive signal COM generated based on COM ′ is also deformed. Therefore, the amount and speed of ink droplets ejected from the piezo element PZT can be accurately controlled. There is a risk that it will not be possible.

The drive signal COM for controlling the drive of the piezo element PZT is COM ′ and ground (G
ND) is generated by amplifying the potential difference with ND). Therefore, the potential difference does not change if both COM ′ and the ground (GND) are affected by the same noise.
It is unlikely to be a problem when generating a drive signal. However, in FIG. 6, since COM ′ (seventh transmission line) and the ground line (second or tenth transmission line) are arranged at positions separated from each other, if they are affected by exactly the same noise. Is hard to think. That is, when the analog voltage signal COM ′ and the ground (GND) are affected by different noises, the potential difference between the COM ′ and the GND varies, so that an accurate drive signal cannot be generated.

Thus, in the comparative example, when the analog voltage signal COM ′ and the ground (GND) are affected by different disturbances, it is difficult to generate an accurate drive signal COM.

<First Embodiment>
In the first embodiment, a twisted pair cable or a coaxial cable is used as the transmission line of the transmission unit 70. In particular, the transmission line of the analog voltage signal COM ′ and the ground line are combined to form a twisted pair cable or a coaxial cable.

FIG. 7 shows a schematic diagram of a twisted pair cable. A twisted pair cable is a transmission member in which two cables (transmission lines) are twisted together to form a pair, and is also referred to as a twisted pair (twisted) line. The colored cable in FIG. 7 represents the transmission line for the analog voltage signal COM ′, and the white cable represents the ground (GND) line. In the present embodiment, two transmission lines for transmitting other signals (for example, control signals such as the latch signal LAT and the change signal CH) are combined to form a twisted pair cable.

By twisting the two transmission lines, the COM ′ transmission line and the GND line are adjacent to each other. Further, when the head 41 reciprocates (scans) in the moving direction, the position of the cable also changes with the movement of the head 41. However, since the two transmission lines are twisted together, they are always adjacent positions. You can keep the relationship. Therefore, even if COM ′ is affected by noise during signal transmission, adjacent ground lines are also affected by the same noise.

As described above, the drive signal COM for controlling the amount of ink ejected from the piezo element PZT is C
It is generated according to the potential difference between OM ′ and ground (GND). Therefore, even if the voltage waveform of COM ′ is disturbed by the influence of noise, the ground (GND) serving as a reference for the potential difference
) Also has a similar disturbance, the influence on the relative potential difference between COM ′ and GND is small. That is, since the potential difference between COM ′ and the ground (GND) itself does not fluctuate even when receiving noise, the drive signal COM can be obtained by using a twisted pair cable.
It is possible to prevent the waveform shape from being disturbed.

FIG. 8 shows a schematic diagram of a coaxial cable. A coaxial cable is a transmission member composed of a central cable (transmission line) and a cylindrical conductor concentrically surrounding it. In FIG. 8, the colored center cable represents the transmission line for the analog voltage signal COM ′, and the center cable is concentrically surrounded by the white ground line. Two cables that transmit other signals (for example, control signals such as the latch signal LAT and the change signal CH) are combined to form a coaxial cable.

Also in this case, since the COM ′ transmission line and the ground (GND) line are always adjacent to each other, as in the case of the twisted pair cable described above, the COM ′ and the adjacent ground line are affected by the same noise. Will receive. That is, since the potential difference between COM ′ and GND does not change even when receiving noise, the waveform shape of the drive signal COM is less likely to be disturbed.

In this way, by using a twisted pair cable or a coaxial cable for the transmission line and the ground line for transmitting the analog voltage signal COM ′, it is possible to generate an accurate drive signal COM that is resistant to disturbance.

Second Embodiment
When the transmission unit 70 is configured using a twisted pair cable or a coaxial cable as shown in the first embodiment, when the head 41 reciprocates, the cable itself may hinder the operation.

For example, in a large format printer that prints on an A0 or A1 size medium, the distance that the head 41 moves (scans) in the direction of movement during printing becomes longer (see FIG. 2A). The transmission line (transmission unit 70) to be connected becomes longer accordingly. Here, if the transmission unit 70 is an FFC as described above, it is unlikely to be a problem because all the transmission lines move together. However, when the transmission unit 70 is composed of a plurality of twisted pair cables or coaxial cables, each cable moves freely as the head 41 moves, so that the cables may become tangled or other units of the printer. Or the print operation may be hindered.

Therefore, in the second embodiment, a part of a certain transmission line and a part of another transmission line among a plurality of transmission lines of the transmission unit 70 (for example, transmission lines constituting a plurality of twisted pair cables or coaxial cables) are joined. Then, by gathering the transmission lines so as not to be separated, the head 4
The movement operation of 1 is not interfered.

FIG. 9 shows a schematic diagram of the transmission unit 70 in the second embodiment. In FIG. 9, the transmission unit 70 is configured by a twisted part made up of a plurality of twisted pair cables arranged in parallel and a ribbon-like part in which transmission lines are joined to each other.

The “twisted portion” in the figure is composed of a normal twisted pair cable, as in the first embodiment. In the cross section of the twist portion (the AA cross section in the figure), the colored cable and the white cable are each paired. In the twisted portion, adjacent pairs are not fixed, so that each pair can move freely.

On the other hand, in the “ribbon-like portion” in the figure, the individual cables are arranged in a line without twisting the two cables. In the cross section of the ribbon-like portion (BB cross section in the figure)
A pair of colored cables and white cables are alternately arranged, and the covering portions of the cables are joined to each other, so that the entire cable forms a wide plane such as a ribbon. By adopting a ribbon shape, the cables are combined together to behave like an FFC in that portion, and the whole of the plurality of cables moves integrally.

As described above, the transmission unit 70 may be long in a large format printer. Therefore, as shown in FIG. 9, a ribbon-like portion is provided between the twisted portions and the transmission lines are joined to each other so that the transmission lines of the transmission unit 70 are not separated. That is, by joining a part of a certain transmission line and a part of another transmission line, each transmission line is moved integrally. The ratio of the ribbon-like portion in the entire transmission unit 70 is reduced, and the proportion of the twisted portion is increased as much as possible, thereby reducing the influence of noise received during signal transmission, and the head 41 reciprocates over a long distance ( When scanning, the cable is prevented from being entangled with each other. Thereby, the transmission part 70 which does not interfere with the operation of the head 41 can be formed. Also, if both ends of the transmission unit 70 are ribbon-shaped, the arrangement of each cable (
(Order of arrangement) is fixed, so that the main substrate Base_M or the head substrate Base_H,
When connecting to the transmission unit 70, it is possible to make it difficult to cause a transmission line connection error.

In addition, although FIG. 9 demonstrated the example using a twisted pair cable, even when using a coaxial cable, by joining a part of the cables and forming a ribbon shape, the cables are prevented from being tangled with each other, The same effect as that of the twisted pair cable can be obtained.

<Third Embodiment>
FIG. 10 shows a schematic diagram of the transmission unit 70 in the third embodiment. In the third embodiment, the transmission line that transmits the analog voltage signal COM ′ and the ground line that is a pair of the COM ′ are separated from other transmission lines (control signal and power transmission line). Then, COM ′ and GND are twisted pair cables or coaxial cables, and the other transmission lines are FFC as described in the comparative example.
To configure. That is, a signal (for example, a control signal such as the latch signal LAT) that is unlikely to hinder the generation of an accurate drive signal COM even under the influence of noise is transmitted by FFC. Then, an analog voltage signal COM ′, which is difficult to generate an accurate drive signal COM when affected by noise, is paired with a ground line, and transmitted with a cable different from the FFC adjacent to each other.

In the configuration of the present embodiment, as in the first embodiment, even if it is affected by noise during signal transmission, the potential difference between COM ′ and GND does not fluctuate.
M can be generated. Further, since the transmission unit 70 can be formed with a simple configuration of only FFC and one type of twisted pair cable or coaxial cable, the cables are tangled when the head 41 reciprocates (scans) during printing. It becomes easier to suppress. Further, since the number of parts is reduced, the manufacturing cost can be reduced, and maintenance is facilitated.

<Summary>
In the printer of the present embodiment, the piezo element PZT in the control unit (drive signal generation unit).
The analog voltage signal COM ′ is generated based on a digital signal (DAC value) that defines the waveform shape of the drive signal COM that drives the signal. The generated COM ′ is transmitted to the head unit via the transmission unit 70, and is subjected to voltage amplification and current amplification in the head unit to be a drive signal COM (voltage waveform signal). Then, the piezo element PZ according to the potential difference between the drive signal COM and the ground.
By driving T, ink is ejected from the nozzle.

In the transmission unit 70, the transmission line for transmitting COM ′ is COM ′ and ground (GN).
D) A twisted pair cable in which the wires are twisted together or a coaxial cable in which the ground wire is concentrically surrounded by the COM ′ transmission line.

Although COM ′ may be affected by disturbances such as noise while being transmitted through the FFC, even if COM ′ receives noise, the paired ground lines also receive the same level of noise. It will be. Therefore, since the potential difference between COM ′ and GND does not change,
The drive signal COM generated by amplifying the potential difference can also have an accurate waveform strong against disturbance.

=== 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
Needless to say, the present invention includes equivalents thereof without departing from the spirit of the invention. In particular, the embodiments described below are also included in the present invention.

<About liquid ejection device>
In each of the above-described embodiments, the printer has been described as an example of the liquid ejection device, 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 PZ is used as an element that performs an operation for ejecting the liquid.
Although T is illustrated, 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 units, 21 paper feed rollers, 22 transport motors,
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 amplification unit, 432 switch, 433 Current amplification unit 50 Detector group, 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 Transmitter,
110 computers,
SOC System-on-a-tip,
PZT Piezo element

Claims (5)

(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 waveform signal generation unit that generates a voltage waveform signal by voltage amplification and current amplification of the analog voltage signal;
An element that is driven according to a potential difference between the voltage waveform signal and the ground, and ejects liquid from a nozzle;
A head portion having
(C) a transmission unit that transmits the analog voltage signal from the control unit to the head unit;
A twisted pair cable in which a transmission line for transmitting the analog voltage signal and a ground line are twisted together;
Or, a transmission unit having a coaxial cable concentrically surrounding a transmission line for transmitting the analog voltage signal, and
A liquid ejection device comprising: The liquid ejection device according to claim 1,
The transmission unit has a plurality of transmission lines for transmitting signals,
Among the plurality of transmission lines, a part of one transmission line and a part of another transmission line are joined. The liquid ejection device according to claim 1 or 2,
The transmission unit is
A liquid ejecting apparatus comprising a flexible flat cable in which a plurality of flat transmission lines are arranged in parallel. The liquid ejection device according to any one of claims 1 to 3,
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. Generating an analog voltage signal based on a digital signal that defines the waveform shape of the signal;
The analog voltage signal is transmitted via a twisted pair cable in which a transmission line for transmitting the analog voltage signal and a ground line are twisted, or a coaxial cable in which a ground line concentrically surrounds the transmission line for transmitting the analog voltage signal. Transmitting to the head,
In the voltage waveform signal generation unit provided in the head unit, voltage amplification and current amplification of the analog voltage signal to generate a voltage waveform signal;
Ejecting liquid from the nozzle by driving the element according to the potential difference between the voltage waveform signal and the ground;
A liquid jetting method.