JP2008221793A - Liquid ejecting apparatus and liquid thickening suppressing method - Google Patents

Abstract

Dispersion of current concentration during thickening suppression operation to suppress supply current of a drive circuit.
A liquid ejection apparatus includes a plurality of pressure chambers, a plurality of elements, a drive signal generation unit, and a signal application unit. The plurality of pressure chambers store liquid and communicate with each of the plurality of nozzles. The plurality of elements cause a pressure change in the liquid stored in the corresponding pressure chamber by the operation accompanying charging / discharging, and are divided into a plurality of groups. The drive signal generation unit repeats a certain period of a drive signal having a plurality of voltage change pattern thickening suppression waveform parts within a certain period, which causes the element to perform a thickening suppression operation that suppresses liquid thickening. To generate repeatedly. The signal applying unit applies a certain thickening suppressing waveform portion within a certain period to the elements belonging to a certain group, and another thickening suppressing waveform within a certain period to the elements belonging to the other group. Apply the waveform section.
[Selection] Figure 9

Description

  The present invention relates to a liquid ejecting apparatus and a liquid thickening suppression method.

  Some liquid ejecting apparatuses that eject liquid from a nozzle perform a thickening suppressing operation for suppressing liquid thickening. In an ink jet printer which is a kind of liquid ejecting apparatus, a micro vibration operation is performed on a piezo element by applying a micro vibration pulse to the piezo element (see, for example, Patent Document 1). This fine vibration operation is an operation for suppressing the thickening of the liquid ink. By this fine vibration operation, a pressure fluctuation that does not cause ink to be ejected from the nozzles is applied to the ink in the pressure chamber.

The micro-vibration pulse is configured as one of a plurality of drive pulses included in the drive signal. The driving signal is repeatedly generated with a certain period as a repeating unit.
JP-A-10-81012

  The fine vibration pulse is shared by a plurality of elements included in the head. For this reason, if the number of nozzles that do not eject liquid increases, a minute vibration pulse is applied to many elements. As a result, a large current flows with the application of the fine vibration pulse to the element, which is a cause of increasing power consumption. Further, due to the increase in the number of nozzles and the number of rows in the head, the current during the fine vibration operation may exceed the current during the ink ejection operation, resulting in an increase in the size of the drive circuit.

  The present invention has been made in view of such circumstances, and an object of the present invention is to suppress the supply current of the drive circuit by dispersing the current concentration and to reduce the size of the drive circuit.

The main invention for achieving the object is as follows:
(A) a plurality of pressure chambers communicating with each of the plurality of nozzles and storing liquid;
(B) A plurality of elements that are provided corresponding to the plurality of pressure chambers and cause a pressure change in the liquid stored in the corresponding pressure chamber by an operation associated with charge and discharge, and are divided into a plurality of groups. A plurality of elements;
(C) A drive signal having a plurality of thickening suppression waveform portions of a voltage change pattern for causing the element to perform a thickening suppressing operation for suppressing the liquid thickening within a certain period, and repeating the certain period as a unit A drive signal generator that repeatedly generates
(D) A signal applying unit that applies a necessary portion of the drive signal to the element,
The element belonging to a certain group is caused to perform the thickening suppressing operation by applying a certain thickening suppressing waveform portion within the certain period, and the element belonging to another group includes the or A signal applying unit that performs the thickening suppressing operation by applying another thickening suppressing waveform portion within a period of
(E).

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

At least the following will be made clear by the description of the present specification and the accompanying drawings.
That is, (A) a plurality of pressure chambers that communicate with each of the plurality of nozzles and store liquid, and (B) a pressure chamber that is provided corresponding to the plurality of pressure chambers and that corresponds to the operation associated with charging / discharging. A plurality of elements that cause a pressure change in the stored liquid, and a plurality of elements divided into a plurality of groups; and (C) the element is caused to perform a thickening suppression operation that suppresses the viscosity increase of the liquid. A drive signal generation unit that repeatedly generates a drive signal having a plurality of waveform portions for suppressing thickening of a voltage change pattern within a certain period, and (D) a necessary part of the drive signal; A signal applying unit to be applied to the element, wherein the element belonging to a certain group is caused to perform the thickening suppressing operation by applying a certain thickening suppressing waveform part within the certain period, The element belonging to another group Makes it possible to realize a liquid ejection apparatus having (E) a signal applying unit that performs the thickening suppressing operation by applying another thickening suppressing waveform unit within the certain period. .
According to such a liquid ejection apparatus, a certain thickening suppressing waveform portion is applied to an element belonging to a certain group within a certain period, and another thickening suppressing waveform is applied to an element belonging to another group. A waveform portion is applied. For this reason, the execution timing of the thickening suppression operation can be made different between elements belonging to a certain group and elements belonging to another group. Thereby, the amount of current (maximum current value) required for charging / discharging the elements can be reduced as compared with the case where the elements belonging to each group are operated with a common waveform section. As a result, it is possible to design the driver circuit while suppressing the supply current of the driver circuit during the thickening suppressing operation, and the driver circuit can be downsized.

In this liquid ejection apparatus, it is preferable that the thickening suppressing operation is an operation for giving a change in pressure to the extent that the liquid is not ejected from the nozzle to the liquid stored in the pressure chamber.
According to such a liquid ejecting apparatus, the meniscus can be vibrated in the nozzle by a pressure change applied to the liquid stored in the pressure chamber. Thereby, the thickening of the liquid in the vicinity of the nozzle can be efficiently suppressed.

In this liquid ejection apparatus, it is preferable that the element is deformed along with charge / discharge to deform a partition film that partitions a part of the pressure chamber.
According to such a liquid ejecting apparatus, it is possible to efficiently give a pressure change to the liquid stored in the pressure chamber.

In this liquid ejecting apparatus, it is preferable that the thickening suppressing waveform section has a trapezoidal voltage change pattern in which a voltage is changed between a reference voltage and a voltage different from the reference voltage.
According to such a liquid ejecting apparatus, it is possible to efficiently give a pressure change to the liquid stored in the pressure chamber.

In this liquid ejection apparatus, it is preferable that the plurality of elements are divided into the plurality of groups based on the type of liquid to be ejected.
According to such a liquid ejecting apparatus, it is possible to perform the thickening suppressing operation at the same timing for each type of liquid to be ejected.

In this liquid ejection apparatus, the signal application unit may determine the number of the thickening suppression waveform portions to be applied to the element within the certain period according to the degree of ease of thickening in the liquid. It is preferable to make them different.
According to such a liquid ejection apparatus, it is possible to optimize the thickening suppression operation for each type of liquid to be ejected.

In such a liquid ejection apparatus, the drive signal generation unit may include the plurality of types of the thickening suppressing waveform units in which the voltage change pattern is determined so that the degree of suppression of the thickening of the liquid is different. Generating a drive signal having a period, and the signal applying unit includes a waveform suppressing waveform unit applied to the element within the certain period in accordance with a degree of ease of thickening in the liquid. It is preferable to make the types different.
According to such a liquid ejection apparatus, it is possible to optimize the thickening suppression operation for each type of liquid to be ejected.

In this liquid discharge apparatus, the drive signal further includes a discharge waveform portion of a voltage change pattern for causing the element to perform a liquid discharge operation for discharging the liquid from the nozzle within the certain period. It is preferable.
According to such a liquid ejecting apparatus, it is possible to selectively perform a thickening suppressing operation on the liquid in the pressure chamber corresponding to the nozzle from which the liquid is not ejected.

In this liquid ejection apparatus, the drive signal generation unit generates a part of the thickening suppression waveform part before the ejection waveform part, and the remaining increase after the ejection waveform part. It is preferable to generate a viscosity suppressing waveform portion.
According to such a liquid ejecting apparatus, the landing position of the liquid can be determined at an intermediate position of the virtual region defined by the repetition period.

In this liquid ejection apparatus, it is preferable that the plurality of elements are charged by a common power supply unit.
According to such a liquid ejecting apparatus, a limited capacity of the power supply unit can be used effectively.

It is also clarified that the following liquid thickening suppression method can be realized.
That is, (A1) a plurality of pressure chambers communicating with each of the plurality of nozzles and storing the liquid, and (A2) provided corresponding to the plurality of pressure chambers, and corresponding pressure chambers by operations associated with charge / discharge. A liquid thickening suppression method in a liquid ejection device having a plurality of elements that cause a pressure change in a stored liquid, the plurality of elements divided into a plurality of groups, and (A3), B) A drive signal having a plurality of thickening suppressing waveform portions of a voltage change pattern determined to cause the element to perform a thickening suppressing operation for suppressing the thickening of the liquid within a certain period. Is repeatedly generated as a repeating unit, and (C) the element belonging to a certain group is caused to perform the thickening suppressing operation by applying a certain thickening suppressing waveform portion within the certain period. Said element belonging to a group It is also clear that a liquid thickening suppression method can be realized, in which the thickening suppressing operation is performed by applying another thickening suppressing waveform portion within the certain period (D). Is done.

=== First Embodiment ===
<About liquid ejection device>
There are various types of liquid ejection devices such as a printing device, a color filter manufacturing device, a display manufacturing device, a semiconductor manufacturing device, and a DNA chip manufacturing device, and it is difficult to describe all of them. Therefore, in this specification, an ink jet printer (hereinafter also simply referred to as a printer) as a printing apparatus and a printing system having the printer will be described as an example. The printing system is a system having at least a printing apparatus and a printing control apparatus (ejection control apparatus) that controls the operation of the printing apparatus.

=== Configuration of Printing System ===
FIG. 1 is a block diagram illustrating the configuration of a printing system. The illustrated printing system includes a printer 1, a computer 110, a display device 120, an input device 130, and a recording / reproducing device 140. The printer 1 corresponds to a printing apparatus, and prints an image on a medium such as paper, cloth, or film. The medium is an object to which liquid is ejected, and is, for example, paper S (see FIG. 2). The computer 110 is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer 110 outputs print data corresponding to the image to the printer 1. Computer programs such as application programs and printer drivers are installed in the computer 110. The display device 120 is a CRT display, a liquid crystal display, or the like. The input device 130 is a keyboard, a mouse, or the like. The recording / reproducing device 140 is a flexible disk drive device or the like.

=== Computer 110 ===
<Configuration of Computer 110>
The computer 110 corresponds to a print control device. The computer 110 has a host-side controller 111. A recording / reproducing device 140 is connected to the host-side controller 111. The host-side controller 111 performs various controls in the computer 110, and the display device 120 and the input device 130 are also connected to be communicable. The host controller 111 includes an interface unit 112, a CPU 113, and a memory 114. The interface unit 112 exchanges data with the printer 1. The CPU 113 is an arithmetic processing unit for performing overall control of the computer 110. The memory 114 is for securing an area for storing a computer program used by the CPU 113, a work area, and the like. The CPU 113 performs various controls according to the computer program stored in the memory 114.

  The print data is data in a format that can be interpreted by the printer 1, and includes various command data and dot formation data SI (see FIG. 7). 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 dot formation data SI is data relating to dots formed on a medium such as the paper S (data such as dot color and size) and is determined for each unit area. Here, the unit area refers to a virtually defined rectangular area on the medium, and the size and shape are determined according to the printing resolution. Further, a printing period Tp (corresponding to a repetition period) in a driving signal COM (see FIG. 6) described later corresponds to a unit area. That is, the printing period Tp is a period necessary for the nozzle Nz (see FIG. 3) of the head 41 to pass over the unit area.

  The dot formation data SI in the present embodiment is composed of dot gradation data indicating the size of dots. The size of the dot is determined by the amount of ink (corresponding to a kind of liquid) to be ejected. For this reason, the dot formation data SI corresponds to ejection amount information indicating the amount of ejected ink. More specifically, the dot formation data SI is composed of 2-bit data. For example, the dot formation data SI includes data [00] corresponding to no dot (no ink ejection), data [01] corresponding to the formation of small dots, and data [10] corresponding to the formation of medium dots. And data [11] corresponding to the formation of large dots. Therefore, the printer 1 can form an image with four gradations for one unit area.

=== Printer 1 ===
<About the configuration of the printer 1>
Next, the configuration of the printer 1 will be described. As shown in FIG. 1, the printer 1 includes a paper transport mechanism 20, a carriage movement mechanism 30, a head unit 40, a detector group 50, a printer-side controller 60, a drive signal generation circuit 70, and a power supply unit PWS. The head unit 40 includes a head controller HC and a head 41. The printer-side controller 60 controls the control target unit based on the print data received from the computer 110 and prints an image on the paper S. That is, the printer-side controller 60 controls the paper transport mechanism 20, the carriage moving mechanism 30, the head unit 40 (head controller HC, head 41), and the drive signal generation circuit 70. Each detector in the detector group 50 monitors the situation in the printer 1 and outputs the detection result to the printer-side controller 60. Upon receiving the detection results from each detector, the printer-side controller 60 uses the detection results when controlling the control target unit.

<Regarding the paper transport mechanism 20>
The paper transport mechanism 20 corresponds to a medium transport unit that transports a medium. The paper transport mechanism 20 feeds the paper S as a medium to a printable position, or transports the paper S by a predetermined transport amount in the transport direction. This transport direction is a direction that intersects the carriage movement direction described below. For example, as shown in FIG. 2, the paper transport mechanism 20 includes a transport motor 21, a transport roller 22, a platen 23, and a paper discharge roller 24. The transport motor 21 is a drive source for transporting the paper S in the transport direction. The conveyance roller 22 is a roller for conveying the paper S to a printable area. The platen 23 is a member for supporting the paper S from the back side. The paper discharge roller 24 is a roller for carrying the paper S that has been printed.

<About the carriage moving mechanism 30>
The carriage moving mechanism 30 is for moving the carriage CR to which the head unit 40 is attached in the carriage moving direction. The carriage movement direction includes a movement direction from one side to the other side and a movement direction from the other side to the one side. Here, the carriage moving mechanism 30 corresponds to a nozzle moving unit that moves the nozzle Nz of the head 41. The carriage movement direction corresponds to the nozzle movement direction in which the nozzle Nz is moved. The carriage moving mechanism 30 includes a carriage motor 31, a guide shaft 32, a timing belt 33, a drive pulley 34, and an idler pulley 35. The carriage motor 31 corresponds to a drive source for moving the carriage CR. A drive pulley 34 is attached to the rotation shaft of the carriage motor 31. The drive pulley 34 is disposed on one end side in the carriage movement direction. An idler pulley 35 is disposed on the other end side in the carriage movement direction on the opposite side to the drive pulley 34. The timing belt 33 is connected to the carriage CR and is spanned between a drive pulley 34 and an idler pulley 35. The guide shaft 32 supports the carriage CR in a movable state. The guide shaft 32 is attached along the carriage movement direction. Accordingly, when the carriage motor 31 operates, the carriage CR moves along the guide shaft 32 in the carriage movement direction.

<About the head unit 40>
The head unit 40 includes a head 41 that ejects ink toward the paper S. The head unit 40 is attached to the carriage CR. And the head 41 which this head unit 40 has is provided in the lower surface of a head case (not shown). The head control unit HC included in the head unit 40 is disposed inside the head case. The head controller HC will be described later.

<About the head 41>
The head 41 is a type of liquid ejection head that ejects liquid. The head 41 illustrated in FIG. 3 includes a nozzle Nz, a pressure chamber 411, a common ink chamber 412, and a piezo element 413. The nozzles Nz are portions serving as ink ejection ports, and a plurality of nozzles Nz are provided at a predetermined pitch. The pressure chamber 411 is a chamber for storing ink, and a plurality of pressure chambers 411 are provided corresponding to each of the plurality of nozzles Nz. Note that the nozzle Nz and the pressure chamber 411 that are in a corresponding relationship are in communication with each other. The common ink chamber 412 is a portion in which ink from the ink cartridge IC attached to the carriage CR is stored. A plurality of pressure chambers 411 communicate with the common ink chamber 412. Accordingly, the head 41 is provided with a plurality of flow paths corresponding to the nozzles Nz from the common ink chamber 412 through the pressure chamber 411 to the nozzles Nz. When the printer 1 is used, this flow path is filled with ink. The volume of the pressure chamber 411 is changed by the operation of the piezo element 413. That is, a part of the pressure chamber 411 is partitioned by the diaphragm 414 which is a kind of partition film.

  A plurality of piezoelectric elements 413 are provided on the surface of the diaphragm 414 opposite to the pressure chambers 411 corresponding to each of the plurality of pressure chambers 411. In other words, it is provided corresponding to each of the plurality of nozzles Nz. As shown in FIG. 5, the piezo elements 413 are connected in parallel to a common power supply unit PWS. The piezo element 413 has, for example, a configuration in which a piezoelectric body is sandwiched between an upper electrode and a lower electrode (both not shown), and is deformed by applying a potential difference between these electrodes. In this example, when the potential of the upper electrode is increased, the piezoelectric body is charged, and accordingly, the piezoelectric element 413 is bent (that is, deformed) so as to protrude toward the pressure chamber 411 side. Further, when the electric potential of the upper electrode is lowered to discharge the piezoelectric body, the piezo element 413 is deformed to reduce the degree of bending. As the piezoelectric element 413 is deformed, the diaphragm 414 is also deformed. As a result, the volume of the pressure chamber 411 changes. In this example, the higher the degree of charge, the greater the amount of deflection of the piezo element 413 and the pressure chamber 411 contracts. Therefore, by controlling the volume of the pressure chamber 411, ink can be ejected from the nozzle Nz, or a fine vibration operation (described later) for preventing the ink from thickening can be performed. The amount of deformation of the piezo element 413 is determined by the application part (partial signal described later) in the drive signal COM. That is, it can be said that the piezo element 413 is deformed according to the potential given by the applied drive signal COM.

  As can be seen from the above description, each piezo element 413 is a plurality of elements that operate to discharge ink by charging and discharging, and corresponds to a plurality of elements that contract the volume of the pressure chamber 411 by charging. The head 41 uses a piezo element 413 as an element that performs an operation for ejecting ink. The deformation amount of the piezo element 413 is accurately determined depending on the state of charge. For this reason, it is possible to control the ink ejection amount with high accuracy by charging and discharging with the drive signal COM. Further, a fine vibration operation can be performed by the applied drive signal COM.

<About nozzle row>
The plurality of nozzles Nz included in the head 41 are grouped for each type of ink to be ejected. For example, as shown in FIG. 4, it has six groups. Specifically, a group belonging to the black ink nozzle row Nk that discharges black ink, a group that belongs to the yellow ink nozzle row Ny that discharges yellow ink, a group that belongs to the cyan ink nozzle row Nc that discharges cyan ink, There are a group belonging to the magenta ink nozzle row Nm for ejecting magenta ink, a group belonging to the light cyan ink nozzle row Nlc for ejecting light cyan ink, and a group belonging to the light magenta ink nozzle row Nlm for ejecting light magenta ink.

  As described above, the piezo element 413 is provided for each nozzle Nz. For this reason, it can be said that the plurality of piezo elements 413 included in the head 41 are also divided into a plurality of groups with the nozzle rows Nk to Nlm as units. In the head 41, one nozzle row is constituted by 96 to 180 nozzles Nz arranged at regular intervals in the transport direction of the paper S. Six nozzle rows are provided in the carriage movement direction orthogonal to the transport direction.

<Regarding the detector group 50>
The detector group 50 is for monitoring the status of the printer 1. The detector group 50 includes, for example, a linear encoder 51 shown in FIG. The linear encoder 51 outputs a detection signal corresponding to the position of the carriage CR (head 41). In addition to this, the detector group 50 includes a rotary encoder for detecting the rotation amount of the transport roller 22 and a paper detector for detecting the presence or absence of the paper S (none is shown).

<About the printer-side controller 60>
As shown in FIG. 1, the printer-side controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a control unit 64. The interface unit 61 exchanges data with the computer 110 which is an external device. The CPU 62 is an arithmetic processing unit for performing overall control of the printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and is configured by a storage element such as a RAM, an EEPROM, or a ROM.

  The CPU 62 controls each control target unit according to the computer program stored in the memory 63. For example, the CPU 62 controls the paper transport mechanism 20 and the carriage moving mechanism 30 via the control unit 64. Further, the CPU 62 outputs a head control signal for controlling the operation of the head 41 to the head controller HC, and outputs a control signal for generating the drive signal COM to the drive signal generation circuit 70. This control signal is also called a DAC value and corresponds to waveform information for determining the waveform of the drive signal COM.

  For example, as shown in FIG. 7, the head control signal includes a clock CLK, dot formation data SI, a latch signal LAT, and a change signal CH. Among these signals, the latch signal LAT has a latch pulse, and the change signal CH has a change pulse. These latch pulse and change pulse correspond to timing pulses for defining the timing for applying the necessary portion of the drive signal COM to the piezo element 413.

<About the drive signal generation circuit 70>
The drive signal generation circuit 70 generates a drive signal COM that is used in common for the plurality of piezo elements 413, and corresponds to a drive signal generation unit. As shown in FIG. 5, the drive signal generation circuit 70 includes a waveform generation circuit 71 and a current amplification circuit 72. The waveform generation circuit 71 generates a voltage waveform signal COM ′ having a voltage waveform that is a basis of the drive signal COM based on the DAC value (waveform information). The current amplification circuit 72 amplifies the current of the voltage waveform signal COM ′ and outputs it as a drive signal COM. The current amplifying circuit 72 includes, for example, an NPN transistor 721 and a PNP transistor 722 that are complementarily connected. The NPN transistor 721 is a transistor that operates when the voltage of the drive signal COM increases (when the piezo element 413 is charged). The PNP transistor 722 is a transistor that operates when the voltage of the drive signal COM drops (when the piezo element 413 is discharged). The operation of the current amplification circuit 72 is controlled by the voltage waveform signal COM ′ output from the waveform generation circuit 71. Therefore, the drive signal COM output from the current amplifier circuit 72 has a voltage waveform that follows the voltage waveform signal COM ′.

<About the drive signal COM>
Here, the drive signal COM will be described. As shown in FIG. 6, the drive signal COM is repeatedly generated every printing period Tp (corresponding to a certain period) which is also a repeating unit. This drive signal COM is composed of eight partial signals. That is, the drive signal COM is generated in the first partial signal SS1 generated in the period Tp1, the second partial signal SS2 generated in the period Tp2, the third partial signal SS3 generated in the period Tp3, and the period Tp4. The fourth partial signal SS4, the fifth partial signal SS5 generated in the period Tp5, the sixth partial signal SS6 generated in the period Tp6, the seventh partial signal SS7 generated in the period Tp7, and the period Tp8 It has an eighth partial signal SS8. Each partial signal SS1 to SS8 has a constant voltage section and a drive pulse. The constant voltage portion is a constant portion of the reference voltage, and each drive pulse is determined in a voltage change pattern for causing the piezo element 413 to perform a predetermined operation.

  In the drive signal COM, the first partial signal SS1 has a first slight vibration pulse PS1a, and the second partial signal SS2 has a second fine vibration pulse PS1b. Similarly, the third partial signal SS3 has a third fine vibration pulse PS1c, the fourth partial signal SS4 has a fourth fine vibration pulse PS1d, and the fifth partial signal SS5 has a fifth fine vibration pulse PS1e. The partial signal SS6 has a sixth micro-vibration pulse PS1f. Further, the seventh partial signal SS7 has a first ejection pulse PS2, and the eighth partial signal SS8 has a second ejection pulse PS3. Each of the fine vibration pulses PS1a to PS1f and each of the ejection pulses PS2 and PS3 is a kind of drive pulse.

  Each of the fine vibration pulses PS1a to PS1f is defined in a voltage change pattern that causes the piezo element 413 to perform a fine vibration operation (corresponding to a thickening suppression operation) for preventing the ink from thickening. For this reason, each of the fine vibration pulses PS1a to PS1f corresponds to a thickening suppressing waveform portion of a voltage change pattern that causes the piezo element 413 to perform a thickening suppressing operation for suppressing the thickening of the liquid. On the other hand, each of the ejection pulses PS2 and PS3 is defined as a voltage change pattern that causes the piezo element 413 to perform an ink ejection operation (corresponding to a liquid ejection operation) for ejecting a predetermined amount of ink from the nozzle Nz. Therefore, each of the ejection pulses PS2 and PS3 corresponds to an ejection waveform portion of a voltage change pattern that causes the piezo element 413 to perform a liquid ejection operation for ejecting liquid from the nozzle Nz. Therefore, the drive signal COM is a signal repeatedly generated with a certain period (printing period Tp) as a repeating unit, and has a plurality of fine vibration pulses as a thickening suppressing waveform portion within a certain period, This corresponds to a signal having a plurality of ejection pulses as ejection waveform portions.

<About micro vibration pulse>
In the present embodiment, each of the first micro-vibration pulse PS1a to the sixth micro-vibration pulse PS1f is determined to have the same voltage waveform (voltage change pattern). These fine vibration pulses PS1a to PS1f are constituted by trapezoidal waves convex downward. Taking the first micro-vibration pulse PS1a as an example, the first micro-vibration pulse PS1a includes a voltage lowering portion Sa that lowers the voltage from the reference voltage Vc to the micro-vibration voltage Vv at a certain degree, and a constant constant at the micro-vibration voltage Vv. The voltage unit Sb and the voltage increasing unit Sc that increases the voltage from the micro-vibration voltage Vv to the reference voltage Vc with a certain degree.

  When one minute vibration pulse is applied, the piezo element 413 performs a minute vibration operation. Prior to this fine vibration operation, the piezo element 413 is kept in a reference deformed state corresponding to the reference voltage Vc. When the voltage drop portion Sa is applied, the degree of charging of the piezo element 413 decreases following the voltage of the voltage drop portion Sa. Along with this, the piezo element 413 is deformed so that the degree of bending becomes small. As the piezo element 413 is deformed, the diaphragm 414 is also deformed, and the volume of the pressure chamber 411 is increased. When the volume of the pressure chamber 411 increases, the ink stored in the pressure chamber 411 is depressurized. As a result, the meniscus (the free surface of the ink exposed at the nozzle Nz) is drawn toward the pressure chamber 411. The bending state of the piezo element 413, that is, the bending state at the end of the application of the voltage drop portion Sa, is maintained over the period during which the constant voltage portion Sb is applied. During this period, the meniscus is in free vibration. After the constant voltage portion Sb is applied, the voltage increasing portion Sc is applied to the piezo element 413. When the voltage increasing portion Sc is applied, the degree of charging of the piezo element 413 increases following the voltage of the voltage increasing portion Sc. Then, the piezo element 413 is deformed so that the degree of bending becomes large. As the piezoelectric element 413 is deformed, the diaphragm 414 is also deformed, and the volume of the pressure chamber 411 is reduced. When the volume of the pressure chamber 411 decreases, the ink stored in the pressure chamber 411 is pressurized. As a result, the meniscus is pushed out in the discharge direction opposite to the pressure chamber 411.

  As described above, when a certain minute vibration pulse is applied to the piezo element 413, the ink stored in the pressure chamber 411 is subjected to a relatively weak pressure change such that the ink is not ejected from the nozzle Nz. The meniscus moves in the direction of the pressure chamber 411 and the ejection direction inside the nozzle Nz in accordance with the change in the pressure of the ink in the pressure chamber 411. Due to the movement of the meniscus, the ink is agitated by the nozzle Nz, and the thickening of the ink is suppressed. In addition, since the meniscus is exposed to the outside air, the ink stored in the head 41 tends to thicken more on the nozzle Nz side than on the pressure chamber 411 side. Therefore, the ink thickening can be effectively suppressed by moving the meniscus and stirring the ink inside the nozzle Nz.

  As can be seen from the above description, each of the fine vibration pulses PS1a to PS1f corresponds to a thickening suppressing waveform portion, and causes the piezo element 413 to perform a thickening suppressing operation for suppressing the thickening of the liquid. The fine vibration operation corresponds to an operation for giving a pressure change to the ink stored in the pressure chamber 411 such that the ink is not ejected from the nozzle Nz. When such a fine vibration operation is performed, the thickening of the ink in the vicinity of the nozzle Nz can be efficiently suppressed by the meniscus that vibrates inside the nozzle Nz. Further, since this fine vibration operation is an operation of deforming the vibration plate 414 (partition film), a pressure change can be efficiently applied to the ink stored in the pressure chamber 411. Further, each of the fine vibration pulses PS1a to PS1f is configured by a trapezoidal wave-like voltage change pattern that changes the voltage between the reference voltage Vc and the fine vibration voltage Vv (corresponding to a voltage different from the reference voltage Vc). Therefore, the pressure change can be efficiently applied to the ink stored in the pressure chamber 411.

<Discharge pulse>
The ejection pulses (first ejection pulse PS2, second ejection pulse PS3) in the present embodiment correspond to ejection waveform portions, and are defined in a voltage change pattern for ejecting a predetermined amount of ink from the nozzles Nz.

  First, the first ejection pulse PS2 will be described. The first ejection pulse PS2 includes a first voltage drop part Sd, a first constant voltage part Se, a voltage rise part Sf, a second constant voltage part Sg, and a second voltage drop part Sh. The first voltage drop unit Sd drops the voltage from the reference voltage Vc to the lowest voltage VL1 with a certain degree. The first constant voltage unit Se maintains the minimum voltage VL1. The voltage raising unit Sf raises the voltage at a certain degree from the lowest voltage VL1 to the highest voltage VH1. In this voltage increase portion Sf, the voltage increase degree is determined as steep as possible. The second constant voltage unit Sg maintains the maximum voltage VH1. The second voltage drop unit Sh drops the voltage from the highest voltage VH1 to the reference voltage Vc with a certain degree. When the first ejection pulse PS2 is applied to the piezo element 413, the volume of the pressure chamber 411 once increases with the application of the first voltage drop unit Sd, and then decreases rapidly with the application of the voltage increase unit Sf. Become. Thereby, the ink in the pressure chamber 411 is pressurized and the ink is ejected from the nozzle Nz. In the present embodiment, an amount of ink suitable for forming medium dots is ejected from the nozzle Nz. Thereafter, the volume of the pressure chamber 411 returns to the reference volume with the application of the second voltage drop portion Sh.

  Next, the second ejection pulse PS3 will be described. The second ejection pulse PS3 includes a first voltage drop part Si, a first constant voltage part Sj, a first voltage rise part Sk, a second constant voltage part Sl, a second voltage rise part Sm, and a third constant voltage part. It has voltage part Sn and 2nd voltage fall part So. The first voltage drop unit Si drops the voltage from the reference voltage Vc to the lowest voltage VL2 with a certain degree. The minimum voltage VL2 is set to a voltage slightly higher than the minimum voltage VL1 in the first ejection pulse PS2. The first constant voltage unit Sj maintains the minimum voltage VL2. The first voltage increase unit Sk increases the voltage from the lowest voltage VL2 to the discharge voltage VF with a certain degree. The ejection voltage VF is set to a voltage slightly lower than the reference voltage Vc. Further, the degree of voltage increase in the first voltage increase unit Sk is determined as steep as possible. The second constant voltage unit Sl maintains the discharge voltage VF. The second voltage increase unit Sm increases the voltage at a certain degree from the discharge voltage VF to the maximum voltage VH2. The maximum voltage VH2 is set to a voltage slightly lower than the maximum voltage VH1 in the first ejection pulse PS2. The second voltage drop unit So drops the voltage from the highest voltage VH2 to the reference voltage Vc with a certain degree. When this second ejection pulse PS3 is applied to the piezo element 413, the volume of the pressure chamber 411 once increases with the application of the first voltage drop part Si, and then suddenly increases with the application of the first voltage rise part Sk. Becomes smaller. Thereby, the ink in the pressure chamber 411 is pressurized and the ink is ejected from the nozzle Nz. In the present embodiment, an amount of ink suitable for forming small dots is ejected from the nozzle Nz. Thereafter, the volume of the pressure chamber 411 changes so as to cancel the residual pressure of the ink in the pressure chamber 411. That is, the volume of the pressure chamber 411 decreases with the application of the second voltage increasing portion Sm, and then the pressure chamber 411 returns to the reference volume with the application of the second voltage decreasing portion So.

  Note that application of a necessary portion of the drive signal COM to the piezo element 413 will be described later.

<About power supply unit PWS>
The power supply unit PWS generates an operation power source for operating each unit of the printer 1 from a commercial power source. There are several types of power supplies for operation. For example, a logic power source (for example, DC 3.3V) for operating the CPU 62, the memory 63, etc., a power source (for example, DC 5V) for operating each detector constituting the detector group 50, the transport motor 21 and the carriage motor There is a power source (for example, DC 12V) for operating 31 and the like, and a power source (for example, DC 42V) used for generating the drive signal COM. In the printer 1, one power supply unit PWS generates a power supply for operation used for each unit. For this reason, the plurality of piezo elements 413 belonging to each of the nozzle arrays Nk to Nlm are charged by the operation power supply generated by the common power supply unit PWS.

<About the head controller HC>
The head control unit HC selects a necessary portion of the drive signal COM based on the dot formation data SI (discharge amount information) and applies it to the piezo element 413 during the dot formation operation for forming dots on the paper S. That is, the head controller HC selects a partial signal (first partial signal SS1 to eighth partial signal SS8) including the fine vibration pulses PS1a to PS1f and the ejection pulses PS2 and PS3 based on the dot formation data SI. . As a result, a drive pulse (fine vibration pulse, ejection pulse) corresponding to the dot formation data SI is applied to the piezo element 413 within the printing period Tp (within a certain period). Such a head controller HC corresponds to a signal applying unit.

  As shown in part in FIG. 5, the head controller HC has six blocks from a block BL (Nk) to a block BL (Nlm). The block BL (Nk) is a block for black ink, and the block BL (Ny) is a block for yellow ink. Similarly, the light magenta block BL (Nlm) is provided for each type of ink to be ejected, in other words, for each nozzle group. In the following description, the black ink block BL (Nk) is also simply referred to as a block BL (Nk). The same applies to other blocks.

  Next, each of the blocks BL (Nk) to BL (Nlm) will be described. Here, since all the blocks BL (Nk) to BL (Nlm) have the same configuration, the configuration of the black ink block BL (Nk) will be described, and the other blocks BL (Ny) to BL (Nlm) will be described. Description of is omitted. As shown in FIG. 7, the block BL (Nk) includes a first shift register 81A, a second shift register 81B, a first latch circuit 82A, a second latch circuit 82B, a control logic 83, and a decoder 84. , And a switch 85. Among these, each part excluding the control logic 83 is provided for each piezo element 413 (for each nozzle Nz).

  In the dot formation operation, the dot formation data SI from the printer-side controller 60 is set in the first shift register 81A and the second shift register 81B. For example, the upper bits of the dot formation data SI are set in the first shift register 81A, and the lower bits of the dot formation data SI are set in the second shift register 81B. The first latch circuit 82A and the second latch circuit 82B latch the data set in the first shift register 81A and the second shift register 81B and make the data for each piezo element 413 (for each nozzle Nz). . Each latch circuit latches the dot formation data SI during the dot formation operation. That is, the first latch circuit 82A latches the upper bits of the dot formation data SI set in the first shift register 81A. The second latch circuit 82B latches the lower bits of the dot formation data SI set in the second shift register 81B. The dot formation data SI set for each piezo element 413 by the latch in each latch circuit is input to the decoder 84.

  The control logic 83 stores switch control information q0 to q3 used for controlling the switch 85. The switch control information q0 to q3 is transmitted from the printer-side controller 60 through the same signal line as the dot formation data SI. Therefore, the control logic 83 includes a switch control information shift register 83a (also referred to as SPSR 83a) and a pattern register 83b that latches the switch control information q0 to q3 set in the SPSR 83a at the timing of the latch pulse. .

  The switch control information q0 to q3 is mainly determined for each gradation, and is information serving as a basis for the switch 85 operation information. The switch control information q0 to q3 during the dot formation operation includes switch control information q0 corresponding to dot non-formation (dot formation data SI [00]) and small dot formation (dot formation data SI [01]). Corresponding switch control information q1, switch control information q2 corresponding to medium dot formation (dot formation data SI [10]), and switch control information q3 corresponding to large dot formation (dot formation data SI [11]) And are prepared. Of these switch control information q0 to q3, the switch control information q0 is determined for each type of ink to be ejected. That is, the fine vibration pulse used for each type of ejected ink is different.

  The switch logic information q0 to q3 is output from the control logic 83 (pattern register 83b). The contents of the switch control information q0 to q3 are updated at a timing specified by a latch pulse included in the latch signal LAT and at a timing specified by a change pulse included in the change signal CH. The specific contents of the switch control information q0 to q3 will be described later.

  The decoder 84 corresponds to a selection output unit. The decoder 84 selects the switch control information q0 to q3 output from the control logic 83 according to the dot formation data SI latched by the latch circuits 82A and 82B, and outputs it to the switch 85 as the switch operation information SW. The switch operation information SW is a signal for controlling on / off of the switch 85. The switch 85 in the present embodiment is turned on when the switch operation information SW is at the H level, and is turned off when the switch operation information SW is at the L level. The drive signal COM is applied to the corresponding piezo element 413 over a period in which the switch 85 is on. Further, when the switch 85 is in the OFF state, the drive signal COM is not applied to the piezo element 413. The output of the switch control information q0 to q3 to the switch 85 will be described later.

=== Printing operation ===
<About overview>
In this printer 1, as a series of printing operations, a printing command receiving operation, a paper feeding operation for transporting the paper S to a printing start position, a dot forming operation for forming dots on the paper S, and a paper S being transported by a predetermined transport amount For example, a transporting operation and a paper discharge operation for discharging the printed paper S are performed. Such a printing operation is performed by the CPU 62 included in the printer-side controller 60. That is, the CPU 62 operates according to the computer program stored in the memory 63 and executes a series of printing operations. Therefore, the computer program has a code for executing a printing operation.

  In this printing operation, an image is printed on the paper S by repeatedly performing the dot formation operation and the conveyance operation. At this time, if the ink is left without being ejected, the ink thickens from the side close to the nozzle Nz. This is presumably because the ink solvent evaporates through the meniscus and the ratio of the color material component in the ink increases. In order to prevent such thickening of the ink, a fine vibration pulse is applied to the corresponding piezo element 413 for the nozzle Nz for which non-dot formation has been selected. As described above, when the fine vibration pulse is applied, the meniscus moves inside the nozzle Nz and the ink is stirred. As a result, ink thickening can be prevented.

  As described above, the drive signal COM of the present embodiment has a plurality of fine vibration pulses PS1a to PS1f within the printing period Tp. When the dot formation data SI indicates non-formation of dots, a certain fine vibration pulse is applied to the plurality of piezo elements 413 corresponding to a certain nozzle row within the printing period Tp, and the other nozzle rows are applied. Another fine vibration pulse is applied to the corresponding plurality of piezo elements 413. With this configuration, the execution timing of the fine vibration operation within the printing period Tp between the plurality of piezo elements 413 corresponding to a certain nozzle row and the plurality of piezo elements 413 corresponding to other nozzle rows. Can be different. Thereby, the amount of current required for charging and discharging the piezo element 413 can be suppressed. That is, the maximum amount of current can be reduced as compared with the case where each piezo element 413 is operated with a common fine vibration pulse. As a result, it is possible to suppress power consumption during the fine vibration operation. Details will be described below.

<Ink ejection operation and micro vibration operation>
As described above, the drive signal COM has a plurality of micro vibration pulses PS1a to PS1f within the printing period Tp. The fine vibration pulse applied to the piezo element 413 is made different for each type of ink. For example, the first slight vibration pulse PS1a is used for the piezo element 413 corresponding to the black ink nozzle row Nk, and the second fine vibration pulse PS1b is used for the piezo element 413 corresponding to the yellow ink nozzle row Ny. Similarly, the third fine vibration pulse PS1c is used for the piezo element 413 corresponding to the cyan ink nozzle row Nc, and the fourth fine vibration pulse PS1d is used for the piezo element 413 corresponding to the magenta ink nozzle row Nm. The fifth fine vibration pulse PS1e is used for the piezo element 413 corresponding to the light cyan ink nozzle row Nlc, and the sixth fine vibration pulse PS1f is used for the piezo element 413 corresponding to the light magenta ink nozzle row Nlm.

  The first ejection pulse PS2 and the second ejection pulse PS3 are used in common for a plurality of piezo elements 413 belonging to each group. That is, when the dot formation data SI indicates the formation of a small dot, the second ejection pulse PS3 is applied to the corresponding piezo element 413. When the dot formation data SI indicates the formation of a medium dot, the first ejection pulse PS2 is applied to the corresponding piezo element 413. When the dot formation data SI indicates the formation of a large dot, the first ejection pulse PS2 and the second ejection pulse PS3 are successively applied to the corresponding piezo elements 413. For this reason, the switch control information q1 to q3 corresponding to the formation of the small dots, the formation of the medium dots, and the formation of the large dots is the same for each ink (each nozzle row).

  Taking the switch control information q1 to q3 of the black ink nozzle row Nk as an example, as shown in FIG. 8A, the switch control information q1 is composed of 8-bit data [00000001]. The switch control information q2 is composed of data [00000010], and the switch control information q3 is composed of data [00000011]. In the switch control information q1 to q3, the most significant bit indicates application / non-application of the first partial signal SS1. That is, when the most significant bit is data [1], the first partial signal SS1 is applied to the piezo element 413. On the other hand, when the most significant bit is data [0], the first partial signal SS1 is not applied to the piezo element 413. The second bit from the upper side indicates application / non-application of the second partial signal SS2. That is, the second partial signal SS2 is applied to the piezo element 413 in the case of data [1], and is not applied to the piezo element 413 in the case of data [0]. Other bits are associated in the same manner. Briefly, the third bit indicates application / non-application of the third partial signal SS3, and the fourth bit indicates application / non-application of the fourth partial signal SS4. The least significant bit indicates application / non-application of the eighth partial signal SS8.

  Therefore, in the switch control information q1, the eighth partial signal SS8 is applied to the piezo element 413, and an amount of ink suitable for forming a small dot is ejected from the nozzle Nz by the second ejection pulse PS3. In the switch control information q2, the seventh partial signal SS7 is applied to the piezo element 413, and an amount of ink suitable for forming a medium dot is ejected from the nozzle Nz by the first ejection pulse PS2. In the switch control information q3, the seventh partial signal SS7 and the eighth partial signal SS8 are applied to the piezo element 413, and the first ejection pulse PS2 and the second ejection pulse PS3 cause an amount of ink suitable for forming a large dot. It is discharged from the nozzle Nz.

  On the other hand, the switch control information q0 corresponding to the non-formation of dots (dot formation data SI [00]) differs for each ink (each nozzle row Nk to Nlm). As shown in FIG. 8B, the switch control information q0 of the black ink nozzle row Nk is 8-bit data [10000000]. For this reason, when no dot is formed for the black ink, the first partial signal SS1 is applied to the corresponding piezo element 413. Thereby, the fine vibration operation by the first fine vibration pulse PS1a is performed in the period Tp1 within the printing period Tp. The switch control information q0 of the yellow ink nozzle row Ny is data [01000000]. For this reason, when dots are not formed for yellow ink, the second partial signal SS2 is applied to the corresponding piezo element 413. Thereby, the fine vibration operation by the second fine vibration pulse PS1b is performed in the period Tp2 within the printing period Tp.

  Similarly, different data is given for other inks. That is, the switch control information q0 of the cyan ink nozzle row Nc is data [00100000], and the switch control information q0 of the magenta ink nozzle row Nm is data [00010000]. The switch control information q0 for the light cyan ink nozzle row Nlc is data [00001000], and the switch control information q0 for the light magenta ink nozzle row Nlm is data [00000100]. Therefore, for other inks, when dots are not formed, a predetermined partial signal is applied to the corresponding piezo element 413, and a fine vibration operation is performed by a fine vibration pulse included in the partial signal. That is, the third partial signal SS3 is applied to the piezo element 413 corresponding to the cyan ink, and the fine vibration operation by the third fine vibration pulse PS1c is performed in the period Tp3 within the printing period Tp. Further, the fourth partial signal SS4 is applied to the piezo element 413 corresponding to magenta ink, and the fine vibration operation is performed by the fourth fine vibration pulse PS1d in the period Tp4 within the printing period Tp. Similarly, the fifth partial signal SS5 is applied to the piezo element 413 corresponding to the light cyan ink, and the fine vibration operation is performed by the fifth fine vibration pulse PS1e in the period Tp5, and the sixth part corresponding to the light magenta ink. The signal SS6 is applied to the piezo element 413, and the fine vibration operation by the sixth fine vibration pulse PS1f is performed in the period Tp6.

  Next, a specific example during the printing operation will be described. For convenience, a case will be described in which a medium dot is formed by each nozzle Nz of the black ink nozzle row Nk and no dot is formed by other inks. In this case, as shown in FIG. 9, the seventh partial signal SS7 is applied to the plurality of piezo elements 413 corresponding to the black ink nozzle row Nk. Each piezo element 413 operates in accordance with the first ejection pulse PS2 included in the seventh partial signal SS7. As a result, each nozzle Nz in the black ink nozzle row Nk ejects an amount of ink suitable for forming medium dots. Then, the second partial signal SS2 to the sixth partial signal SS6 are selectively applied to the plurality of piezo elements 413 corresponding to the other nozzle rows, and the fine vibration operation is performed by the corresponding fine vibration pulses PS1b to PS1f. . That is, the plurality of piezo elements 413 corresponding to the yellow ink nozzle row Ny perform a fine vibration operation by the second fine vibration pulse PS1b. The plurality of piezo elements 413 corresponding to the cyan ink nozzle row Nc perform a micro vibration operation by the third micro vibration pulse PS1c, and the plurality of piezo elements 413 corresponding to the magenta ink nozzle array Nm perform a micro vibration operation by the fourth micro vibration pulse PS1d. . Similarly, the plurality of piezo elements 413 corresponding to the light cyan ink nozzle row Nlc are microscopically affected by the fifth fine vibration pulse PS1e, and the plurality of piezo elements 413 corresponding to the light magenta ink nozzle row Nlm are microscopically controlled by the sixth fine vibration pulse PS1f. Perform vibration.

  Here, the power consumption during the printing operation will be described. The main factor that determines the power consumption during the printing operation is the current amplification circuit 72 included in the drive signal generation circuit 70. The current amplifying circuit 72 includes an NPN transistor 721 and a PNP transistor 722. Therefore, the power consumption of the current amplifier circuit 72 is determined by the collector loss of the NPN transistor 721 and the collector loss of the PNP transistor 722. Here, the NPN transistor 721 operates when the voltage of the drive signal COM rises. Therefore, the collector loss of the NPN transistor 721 can be obtained by multiplying the voltage difference between the power supply and the drive signal COM by the collector current (that is, the current that flows when the piezo element 413 is charged). The PNP transistor 722 operates when the voltage of the drive signal COM drops. Therefore, the collector loss of the PNP transistor 722 can be obtained by multiplying the voltage difference between the drive signal COM and the ground by the collector current (that is, the current that flows when the piezo element 413 is discharged).

  The collector loss of the NPN transistor 721 at the time of applying the micro-vibration pulse is calculated by multiplying the voltage difference between the power source and the voltage riser Sc (the region indicated by the hatched portion in the figure) by the charging current Ic1 that flows during charging. Is done. The collector loss of the PNP transistor 722 is calculated by multiplying the voltage difference between the voltage drop portion Sa and the ground (the region indicated by the hatched portion in the drawing) by the discharge current Id1. The collector loss of each transistor at the time of applying each ejection pulse PS2, PS3 is calculated in the same manner. For example, the collector loss of the NPN transistor 721 in the first ejection pulse PS2 is calculated by multiplying the voltage difference between the power supply and the voltage riser Sf by the charging current Ic2. Further, the collector loss of the PNP transistor 722 is the value obtained by multiplying the voltage difference between the first voltage drop portion Sd and the ground by the discharge current Id2, and the voltage difference between the second voltage drop portion Sh and the ground. Is calculated by adding the value obtained by multiplying the current Id3 at the time of discharge to the current.

  In the printer 1 of the present embodiment, as shown in FIG. 9, fine vibration pulses PS1a to PS1f are generated corresponding to the nozzle rows Nk to Nlm and applied to the piezo elements 413 at different times. For example, the second micro-vibration pulse PS1b is applied to the piezo element 413 in the period Tp2, and the third micro-oscillation pulse PS1c is applied to the piezo element 413 in the period Tp3. For this reason, it can prevent effectively that the electric current at the time of charge with respect to the piezoelectric element 413 and the electric current at the time of discharge become large too much. In other words, in each period Tp1 to Tp6 in which the micro-vibration pulses PS1a to PS1f are generated, only a current of an amount for charging / discharging the piezo elements 413 corresponding to one nozzle row flows at the maximum. As a result, the maximum current value resulting from the fine vibration operation can be suppressed.

<Summary of First Embodiment>
In the printer 1 of the first embodiment described above, the drive signal generation circuit 70 includes a plurality of micro vibration pulses PS1a to PS1f in the drive signal COM having the printing period Tp as a repetitive unit. When non-formation of dots is designated in a certain printing period Tp, the head controller HC applies different micro-vibration pulses for each piezo element group defined by the nozzle rows Nk to Nlm. That is, a certain fine vibration pulse is applied to a piezo element group belonging to a certain group, and another fine vibration pulse is applied to a piezo element group belonging to another group. Since the micro-vibration pulses are generated in time series, this configuration allows the micro-vibration operation (thickening suppression operation) to be performed between a piezo element group belonging to a certain group and a piezo element group belonging to another group. The timing can be different. Thereby, the amount of current required for charging and discharging the piezo element 413 can be suppressed. For example, the maximum amount of current can be suppressed as compared with the printer 1 in which one fine vibration pulse is included in the printing period Tp and the fine vibration pulse is shared by each piezo element 413. As a result, it is possible to suppress the current supply capability of the current amplification circuit 72 during the fine vibration operation.

  Further, the drive signal COM includes an ejection pulse (first ejection pulse PS2, second ejection pulse PS3) for ejecting ink. Then, a fine vibration operation is performed on the piezo element 413 corresponding to the nozzle Nz that does not eject ink. Thereby, the fine vibration operation can be selectively performed using the common drive signal COM for the ink in the pressure chamber 411 corresponding to the nozzle Nz from which the ink is not ejected.

  The piezoelectric element groups are grouped based on the type of ink to be ejected. For this reason, the fine vibration operation can be performed at the same timing for each type of ejected ink. Thereby, simplification of control can be achieved.

  Further, the power supply unit PWS included in the printer 1 is shared for charging a plurality of piezo elements 413. Further, by adopting a configuration in which the fine vibration pulse is applied to each group of the piezo elements 413, the limited capacity of the power supply unit PWS can be effectively used.

=== Second Embodiment ===
Next, a second embodiment will be described. The feature of the printer 1 of the second embodiment is mainly the drive signal COM. Briefly, the printer 1 is mainly characterized in that the ejection pulse is generated in the middle of the printing period Tp, that one fine vibration pulse is shared by some nozzle rows, the ink The number of micro-vibration pulses applied differs according to the degree of ease of thickening. Hereinafter, the second embodiment will be described focusing on these points. Note that the configuration of the printer 1 of the second embodiment is the same as that of the printer 1 of the first embodiment. Therefore, the description is omitted.

<Regarding Generated Drive Signal COM2>
As shown in FIG. 10A, the drive signal COM2 in the second embodiment is composed of six partial signals. That is, the drive signal COM2 is generated in the first partial signal SS11 generated in the period Tp11, the second partial signal SS12 generated in the period Tp12, the third partial signal SS13 generated in the period Tp13, and the period Tp14. It has a fourth partial signal SS14, a fifth partial signal SS15 generated in the period Tp15, and a sixth partial signal SS16 generated in the period Tp16.

  In the drive signal COM2, the first partial signal SS11 has a first slight vibration pulse PS1a, and the second partial signal SS12 has a second fine vibration pulse PS1b. The third partial signal SS13 has a first ejection pulse PS2, and the fourth partial signal SS14 has a second ejection pulse PS3. The fifth partial signal SS15 has a third slight vibration pulse PS1c, and the sixth partial signal SS16 has a fourth fine vibration pulse PS1d. The fine vibration pulses from the first fine vibration pulse PS1a to the fourth fine vibration pulse PS1d, and the first ejection pulse PS2 and the second ejection pulse PS3 are the same as those described in the first embodiment. Therefore, the description is omitted.

  In the drive signal COM2, two ejection pulses (first ejection pulse PS2 and second ejection pulse PS3) are continuously formed at an intermediate timing within the printing period Tp. Then, fine vibration pulses are generated before and after both ejection pulses. Furthermore, the number of micro-vibration pulses generated before both ejection pulses and the number of micro-vibration pulses generated after the two ejection pulses are aligned. In this example, two fine vibration pulses (first fine vibration pulse PS1a and second fine vibration pulse PS1b) are generated before both discharge pulses, and two fine vibration pulses (third fine pulse (third fine pulse) are generated after both discharge pulses. The vibration pulse PS1c and the fourth fine vibration pulse PS1d) are generated. Therefore, it can be said that both ejection pulses PS2 and PS3 are generated in the central portion within the printing period Tp.

<Ink ejection operation and micro vibration operation>
Also in the printer 1 of the second embodiment, dot non-formation (fine vibration operation, dot formation data SI [00]), small dot formation (dot formation data SI [01]), medium dot formation (dot formation data SI) [10]) and an image can be formed with four gradations consisting of large dot formation (dot formation data SI [11]).

  The second ejection pulse PS3 is applied to the piezo element 413 when forming small dots, and the first ejection pulse PS2 is applied to the piezo element 413 when forming medium dots. When the large dot is formed, the first ejection pulse PS2 and the second ejection pulse PS3 are continuously applied to the piezo element 413. Here, both ejection pulses PS1 and PS2 are generated in the central portion within the printing period Tp. By adopting this configuration, each dot can be formed near the center in a unit area (a rectangular area virtually defined on the medium). As a result, the image printed on the paper S and the control image can be accurately aligned.

In addition, regarding the fine vibration operation, the number of fine vibration pulses to be applied differs depending on the degree of ease of thickening the ink. As shown in FIG. 10B, in the printer 1, the head controller HC includes a dark color ink composed of black ink, cyan ink, and magenta ink, and a light color composed of yellow ink, light cyan ink, and light magenta ink. The number of micro-vibration pulses applied to the piezo element 413 is different for the system ink. That is, the head controller HC applies two fine vibration pulses to the piezo elements 413 belonging to the group of dark color inks that are relatively easy to thicken, and belongs to the group of light color inks that are relatively hard to thicken. One fine vibration pulse is applied to the piezo element 413. Specifically, the second fine vibration pulse PS1b and the fourth fine vibration pulse PS1d are applied to the piezo element 413 for black ink and magenta ink. The first fine vibration pulse PS1a and the third fine vibration pulse PS1c are applied to the piezo element 413 for cyan ink. On the other hand, the first fine vibration pulse PS1a is applied to yellow ink, the third fine vibration pulse PS1c is applied to light cyan ink, and the fourth fine vibration pulse PS1d is applied to light magenta ink.
By adopting such a configuration, it is possible to perform a fine vibration operation in which the degree of suppression of thickening is increased with respect to dark-colored ink that is more easily thickened than light-colored ink. For light-colored inks, necessary and sufficient fine vibration operation suitable for the degree of ease of thickening can be performed. In addition, by optimizing the number of such fine vibration pulses, power consumption during the fine vibration operation can be suppressed.

Regarding the fine vibration operation, in the printer 1, one fine vibration pulse is shared by a plurality of groups of piezoelectric elements. For example, the first slight vibration pulse PS1a is shared by the yellow ink piezo element group and the cyan ink piezo element group. The second micro-vibration pulse PS1b is shared by the piezo element group for black ink and the piezo element group for magenta ink. The third micro-vibration pulse PS1c is shared by the piezo element group for cyan ink and the piezo element group for light cyan ink. The fourth micro-vibration pulse PS1d is shared by the piezo element group for black ink, the piezo element group for magenta ink, and the piezo element group for light magenta ink.
By adopting such a configuration, the number of micro-vibration pulses can be optimized (can be determined without excess or deficiency), and a problem that the printing period Tp becomes excessively long can be prevented. As a result, the printing speed can be increased.

<Summary of Second Embodiment>
In the printer 1 of the second embodiment described above, the head controller HC varies the number of micro-vibration pulses applied to the piezo element 413 within the printing period Tp according to the degree of ease of thickening the ink. ing. With this configuration, the fine vibration operation can be optimized for each type of ink to be ejected. This optimization can suppress power consumption during the fine vibration operation.

  In the printer 1, the drive signal generation circuit 70 generates some fine vibration pulses before the ejection pulses and generates the remaining fine vibration pulses after the ejection pulses. With this configuration, the ink landing position can be determined at an intermediate position between the unit areas defined by the printing period Tp (virtual areas defined by the repetition period). This increases the consistency between the control image and the image printed on the medium. As a result, a high-quality image can be obtained.

=== Third Embodiment ===
Next, a third embodiment will be described. The feature of the printer 1 of the third embodiment is mainly in the waveform of the fine vibration pulse. Briefly, the dark color ink is characterized in that a fine vibration pulse having a higher voltage change pattern than the fine vibration pulse for light color ink is used. Hereinafter, the third embodiment will be described focusing on this. Note that the configuration of the printer 1 of the third embodiment is the same as that of the first embodiment. Therefore, the description is omitted.

<Regarding Generated Drive Signal COM3>
As shown in FIG. 11A, the drive signal COM3 in the third embodiment is composed of eight partial signals. That is, the drive signal COM3 is generated in the first partial signal SS21 generated in the period Tp21, the second partial signal SS22 generated in the period Tp22, the third partial signal SS23 generated in the period Tp23, and the period Tp24. The fourth partial signal SS24, the fifth partial signal SS25 generated in the period Tp25, the sixth partial signal SS26 generated in the period Tp26, the seventh partial signal SS27 generated in the period Tp27, and the period Tp28. It has an eighth partial signal SS28.

  Similar to the drive signal COM in the first embodiment, the first partial signal SS21 to the sixth partial signal SS26 have fine vibration pulses PS11a to PS11f, respectively. The seventh partial signal SS27 has a first ejection pulse PS2, and the eighth partial signal SS28 has a second ejection pulse PS3. The first ejection pulse PS2 and the second ejection pulse PS3 are the same as those described in the first embodiment. Therefore, the description is omitted.

  The first partial signal SS21 has a first fine vibration pulse PS11a, and the second partial signal SS22 has a second fine vibration pulse PS11b. Similarly, the third partial signal SS23 has a third fine vibration pulse PS11c, the fourth partial signal SS24 has a fourth fine vibration pulse PS11d, and the fifth partial signal SS25 has a fifth fine vibration pulse PS11e. The partial signal SS26 has a sixth slight vibration pulse PS11f. These fine vibration pulses PS11a to PS11f are common to the fine vibration pulses PS1a to PS1f of the first embodiment in that they are constituted by downwardly convex trapezoidal waves. However, the difference between the reference voltage Vc and the micro-vibration voltages Vv1, Vv2 is different from that of the first embodiment. That is, the first fine vibration pulse PS11a, the third fine vibration pulse PS11c, and the fourth fine vibration pulse PS11d used for the dark color ink have a difference between the reference voltage Vc and the fine vibration voltage Vv1 in the first embodiment. The voltage change pattern is determined so as to be larger than the fine vibration pulses PS1a to PS1f. On the other hand, the second micro-vibration pulse PS11b, the fifth micro-vibration pulse PS11e, and the sixth micro-vibration pulse PS11f used for the light color ink are different in the difference between the reference voltage Vc and the micro-vibration voltage Vv2 in the first embodiment. The voltage change pattern is determined so as to be smaller than the vibration pulses PS1a to PS1f.

  As a result, for dark-colored inks that are relatively easy to thicken, a fine vibration operation is performed using the fine vibration pulses PS11a, PS11c, and PS11d that have a high degree of suppression of thickening. On the other hand, for light-colored inks with a relatively low degree of increase in viscosity, a micro-vibration operation is performed using micro-vibration pulses PS11b, PS11e, and PS11f with a low degree of suppression of thickening. For this reason, the micro-vibration operation can be optimized in accordance with the degree of ease of thickening the ejected ink. In addition, in the case of a micro vibration pulse with a low degree of suppression of thickening, the amount of current that flows can be suppressed. For this reason, power consumption can also be suppressed.

=== Other Embodiments ===
The above-described embodiment describes a printing system having the printer 1, which includes disclosure of a liquid discharge method, a liquid discharge system, and the like. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the group of piezo elements 413>
In the printer 1 of each embodiment described above, the nozzle rows Nk to Nlm are provided for each type of ink to be ejected. For this reason, the piezo elements 413 are grouped for each nozzle row. Here, the group of the piezo elements 413 is not limited to the unit of nozzle rows, but is defined by various standards.

  For example, the head 41 shown in FIGS. 12A and 12B includes a first black ink nozzle row Nk1, a second black ink nozzle row Nk2, and a color ink nozzle row Ncl. The first black ink nozzle row Nk1 has a plurality of nozzles Nz formed at a predetermined pitch in the transport direction, and ejects black ink. The second black ink nozzle row Nk2 is a plurality of nozzles Nz formed at a predetermined pitch in the transport direction, and is displaced from the plurality of nozzles Nz constituting the first black ink nozzle row Nk1 in the transport direction. It has a plurality of formed nozzles Nz and discharges black ink. The color ink nozzle row Ncl is a plurality of nozzles Nz formed at a predetermined pitch in the transport direction, and a plurality of nozzles Nz constituting the second black ink nozzle row Nk2 are aligned in the transport direction. A different color ink is ejected for each nozzle group having a predetermined number of nozzles Nz that have Nz and are adjacent in the transport direction. The color ink nozzle row Ncl includes a cyan ink nozzle group GR1 that discharges cyan ink, a magenta ink nozzle group GR2 that discharges magenta ink, and a yellow ink nozzle group GR3 that discharges yellow ink.

  In the head 41 having such a configuration, the group of piezo elements 413 includes the first black ink nozzle row Nk1, the second black ink nozzle row Nk2, the cyan ink nozzle group GR1, the magenta ink nozzle group GR2, and the yellow ink nozzle group. It is determined based on each of GR3. Even with such a configuration, the same operational effects as those of the above-described embodiments can be obtained.

<Voltage change pattern of micro vibration pulse>
Each micro-vibration pulse PS1a to PS1f in each of the embodiments described above is configured by a downwardly convex trapezoidal wave, but is not limited to this configuration. The voltage change pattern of the fine vibration pulse can be arbitrarily determined as long as it gives the ink in the pressure chamber 411 a pressure change that does not eject ink. For example, an upward convex trapezoidal wave or a trapezoidal wave may not be used.

<Performance period of slight vibration operation>
In each of the above-described embodiments, the fine vibration operation in the printing period Tp has been described as an example, but the present invention is not limited to this period. The same can be applied to a fine vibration operation other than the printing period Tp. For example, the present invention can be similarly applied to a fine vibration operation before printing performed before the paper S reaches the head 41. Further, the present invention can be similarly applied to a fine vibration operation performed after the end of a certain printing operation until the start of the next printing operation. In these cases, the repetition period of the drive signal is appropriately determined according to the number of micro-vibration pulses generated.

<About an element that operates to discharge liquid>
In each of the above-described embodiments, the piezo element 413 is exemplified. However, the piezo element 413 is not limited to the piezo element 413 as long as the element operates to discharge liquid along with charge / discharge.

<About other devices>
The printer 1 in each of the embodiments described above is of a type that performs printing by reciprocating the head 41 in the carriage movement direction, but is not limited to this configuration. For example, it may be a line head printer having a line head in which a plurality of nozzles Nz are arranged across the width direction of the medium. Further, other liquid ejection devices other than the printing device may be used. In this case, the liquid to be discharged is suitable for the apparatus.

<Discharged liquid>
In the second embodiment and the third embodiment described above, dark color ink is used as an example of ink that tends to thicken, and light color ink is used as an example of ink that is difficult to thicken. In addition to these, examples of inks that tend to thicken include pigment-based inks in addition to dark-colored inks, and examples of inks that are difficult to thicken include dye-based inks. The ease of thickening varies depending on the ink components.

  The same applies to other liquid ejection devices other than the printing device, and the ease of thickening differs depending on the type of liquid to be ejected.

1 is a block diagram illustrating a configuration of a printing system. FIG. 2 is a perspective view illustrating a configuration of a printer. It is sectional drawing for demonstrating the structure of a head. It is a figure explaining the structure of a nozzle row. It is a block diagram explaining the relationship between a drive signal generation circuit and a peripheral part. It is a figure for demonstrating the drive signal of 1st Embodiment. It is a block diagram for demonstrating the structure of a head control part. FIG. 8A is a diagram illustrating switch control information for the black ink nozzle row. FIG. 8B is a diagram for explaining switch control information for no dots for each nozzle row. It is a figure for demonstrating the specific example of operation | movement. FIG. 10A is a diagram for explaining a drive signal according to the second embodiment. FIG. 10B is a diagram for explaining a micro-vibration pulse used in the second embodiment. FIG. 11A is a diagram for explaining a drive signal according to the third embodiment. FIG. 11B is a diagram for explaining the micro-vibration pulse used in the third embodiment. FIG. 12A is a perspective view of a head having another configuration as viewed from the nozzle side. FIG. 12B is a diagram illustrating nozzle rows in a head having another configuration.

Explanation of symbols

1 printer, 20 paper transport mechanism, 21 transport motor, 22 transport roller,
23 platen, 24 discharge roller, 30 carriage moving mechanism,
31 Carriage motor, 32 guide shaft, 33 timing belt,
34 Drive pulley, 35 idler pulley, 40 head unit,
41 head, 411 pressure chamber, 412 common ink chamber,
413 piezo elements, 414 diaphragms, 50 detector groups,
51 linear encoder, 60 printer controller,
70 drive signal generation circuit, 71 waveform generation circuit, 72 current amplification circuit,
721 NPN type transistor, 722 PNP type transistor,
81A first shift register, 81B second shift register,
82A first latch circuit, 82B second latch circuit, 83 control logic,
84 decoder, 85 switch, 110 computer,
111 Host-side controller, 112 interface unit,
113 CPU, 114 memory, 120 display device, 130 input device,
140 recording / reproducing apparatus, CR carriage, IC ink cartridge,
Nz nozzle, Nk black ink nozzle row,
Ny yellow ink nozzle row, Nc cyan ink nozzle row,
Nm magenta ink nozzle row, Nlc light cyan ink nozzle row,
Nlm light magenta ink nozzle row, Nk1 first black nozzle row,
Nk2 second black nozzle row, Ncl color ink nozzle row,
GR1 cyan ink nozzle group, GR2 magenta ink nozzle group,
GR3 yellow ink nozzle group, HC head controller,
BL head control block, CLK clock,
SI dot formation data, LAT latch signal, CH change signal,
COM 'voltage waveform signal, Tp printing period Tp1-Tp8 period, Tp11-Tp16 period,
Tp21-Tp28 period,
COM drive signal,
SS1 first partial signal, SS2 second partial signal, SS3 third partial signal,
SS4 4th partial signal, SS5 5th partial signal, SS6 6th partial signal,
SS7 7th partial signal, SS8 8th partial signal,
COM2 drive signal,
SS11 first partial signal, SS12 second partial signal,
SS13 third partial signal, SS14 fourth partial signal,
SS15 5th partial signal, SS16 6th partial signal,
COM3 drive signal,
SS21 first partial signal, SS22 second partial signal,
SS23 third partial signal, SS24 fourth partial signal,
SS25 5th partial signal, SS26 6th partial signal,
SS27 7th partial signal, SS28 8th partial signal,
PS1a first fine vibration pulse,
Sa voltage drop part, Sb constant voltage part, Sc voltage rise part,
PS1b second fine vibration pulse, PS1c third fine vibration pulse,
PS1d 4th vibration pulse, PS1e 5th vibration pulse,
PS1f sixth fine vibration pulse, PS11a first fine vibration pulse,
PS11b second fine vibration pulse, PS11c third fine vibration pulse,
PS11d 4th vibration pulse, PS11e 5th vibration pulse,
PS11f 6th vibration pulse,
PS2 first discharge pulse,
Sd first voltage drop part, Se first constant voltage part, Sf voltage rise part,
Sg second constant voltage part, Sh second voltage drop part,
PS3 second discharge pulse,
Si first voltage drop unit, Sj first constant voltage unit, Sk first voltage rise unit,
Sl second constant voltage unit, Sm second voltage rising unit, Sn third constant voltage unit,
So second voltage drop part,
Vc reference voltage,
Vv microvibration voltage, Vv1 microvibration voltage, Vv2 microvibration voltage,
VH maximum voltage, VH1 maximum voltage, VH2 maximum voltage,
VL minimum voltage, VL1 minimum voltage, VL2 minimum voltage,
q0 to q3 Switch control information, SW switch operation information

Claims (11)

(A) a plurality of pressure chambers communicating with each of the plurality of nozzles and storing liquid;
(B) A plurality of elements that are provided corresponding to the plurality of pressure chambers and cause a pressure change in the liquid stored in the corresponding pressure chamber by an operation associated with charge and discharge, and are divided into a plurality of groups. A plurality of elements;
(C) A drive signal having a plurality of thickening suppression waveform portions of a voltage change pattern for causing the element to perform a thickening suppressing operation for suppressing the liquid thickening within a certain period, and repeating the certain period as a unit A drive signal generator that repeatedly generates
(D) A signal applying unit that applies a necessary portion of the drive signal to the element,
The element belonging to a certain group is caused to perform the thickening suppressing operation by applying a certain thickening suppressing waveform portion within the certain period, and the element belonging to another group includes the or A signal applying unit that performs the thickening suppressing operation by applying another thickening suppressing waveform portion within a period of
A liquid ejection apparatus having (E). The liquid ejection device according to claim 1,
The thickening suppressing operation is
A liquid ejecting apparatus, which is an operation of applying a pressure change to the liquid stored in the pressure chamber to such an extent that the liquid is not ejected from the nozzle. The liquid ejection device according to claim 2,
The element is
A liquid ejection apparatus that deforms with charge / discharge to deform a partition film that partitions a part of the pressure chamber. A liquid ejection apparatus according to any one of claims 1 to 3,
The thickening suppressing waveform portion is
A liquid ejection apparatus, which is a trapezoidal voltage change pattern in which a voltage is changed between a reference voltage and a voltage different from the reference voltage. The liquid ejection device according to any one of claims 1 to 4,
The plurality of elements are:
Liquid ejecting apparatuses that are divided into the plurality of groups based on the type of liquid to be ejected. The liquid ejection device according to claim 5,
The signal applying unit is
A liquid ejection apparatus that varies the number of the thickening suppressing waveform portions applied to the element within the certain period in accordance with the degree of ease of thickening in the liquid. The liquid ejection device according to claim 5,
The drive signal generator is
Generating a drive signal having a plurality of types of thickening suppression waveform portions in which the voltage change pattern is determined so that the degree of suppression of thickening of the liquid is different, within the certain period;
The signal applying unit is
A liquid ejection apparatus that varies the type of the thickening suppressing waveform portion applied to the element within the certain period in accordance with the degree of ease of thickening in the liquid. A liquid ejection device according to any one of claims 1 to 7,
The drive signal is
A liquid ejection apparatus, further comprising a discharge waveform portion of a voltage change pattern for causing the element to perform a liquid ejection operation for ejecting the liquid from the nozzle within the certain period. The liquid ejection device according to claim 8, wherein
The drive signal generator is
A liquid ejection apparatus, wherein a part of the thickening suppression waveform part is generated before the ejection waveform part, and the remaining thickening suppression waveform part is generated after the ejection waveform part. A liquid ejection apparatus according to any one of claims 1 to 9, wherein
The plurality of elements are:
A liquid ejection device that is charged by a common power supply unit. (A1) a plurality of pressure chambers communicating with each of the plurality of nozzles and storing liquid;
(A2) A plurality of elements which are provided corresponding to the plurality of pressure chambers and cause a pressure change in the liquid stored in the corresponding pressure chamber by an operation associated with charge / discharge, and are divided into a plurality of groups. A plurality of elements;
In the liquid ejection apparatus having (A3), a liquid thickening suppression method,
(B) a drive signal having a plurality of thickening suppression waveform portions of a voltage change pattern determined to cause the device to perform a thickening suppression operation for suppressing the liquid thickening within a certain period, Generate a period as a repeating unit,
(C) The element belonging to a certain group is caused to perform the thickening suppressing operation by applying a certain thickening suppressing waveform portion within the certain period, and the element belonging to another group is subjected to the above-mentioned By performing another thickening suppressing waveform portion within a certain period, the thickening suppressing operation is performed.
(D) A method for suppressing a thickening of a liquid, characterized in that

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