JP2010162767A - Liquid ejection device and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection device configured to reduce wasteful liquid consumption. <P>SOLUTION: The liquid ejection device (1) includes a head (HD) and ejection control units (30, 40, 60). The head is configured to eject the first liquid through some of a plurality of nozzles and eject the second liquid different in kinds from the first liquid through some other nozzles of the plurality of nozzles. The ejection control units control the head to perform a flashing operation to eject the liquid through the nozzles so that the liquid may not land on an object. Further, the ejection control units control the head so that the amount of the second liquid ejected during the flashing operation may be different from the amount of the first liquid ejected during the flashing operation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus and a control method thereof.

  There are various types of liquid ejection devices that eject liquid from a nozzle to an object, such as a printer, a color filter manufacturing device, and a staining device. In this type of liquid ejection device, a phenomenon occurs in which the liquid in the nozzle is thickened due to evaporation of a solvent component in the liquid. A thickened liquid (hereinafter, also referred to as a thickened liquid) is not preferable because it fluctuates the flight direction of the liquid or causes clogging of the nozzle. In view of this, a liquid ejecting apparatus that performs a flushing operation for ejecting a thickened liquid has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-29996

In performing the flushing operation, a common drive signal is generally used.
For this reason, when a plurality of types of liquids having different easiness of thickening are ejected from a common head, the conditions for flushing are determined according to the liquids that are easily thickened.
In this case, there is a problem that the flushing operation is excessively performed on the liquid that is difficult to thicken, and the liquid is consumed wastefully.
The present invention has been made in view of such circumstances, and an object thereof is to suppress wasteful consumption of liquid.

The main invention for achieving the object is as follows:
A head for discharging the first liquid from a part of the plurality of nozzles and discharging a second liquid of a type different from the first liquid from the other part of the plurality of nozzles;
A discharge control unit for controlling the head to perform a flushing operation for discharging the liquid from the nozzle so as not to land on an object;
An ejection controller that controls the head such that the amount of the second liquid ejected in the flushing operation is different from the amount of the first liquid ejected in the flushing operation;
A liquid ejection apparatus having

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

1 is a block diagram illustrating a configuration of a printing system. 2 is a perspective view illustrating an internal configuration of the printer. FIG. It is the figure which looked at the platen from the upper part. It is sectional drawing of a head. It is a figure explaining a nozzle row. It is a block diagram explaining a drive signal generation circuit. It is a figure explaining a drive signal. FIG. 8A is a diagram illustrating each pulse applied to the piezo element in the printing operation. FIG. 8B is a diagram for explaining the relationship between dot formation data and the operation. FIG. 9A is a diagram illustrating a drive signal used for a strong flushing operation. FIG. 9B is a diagram illustrating the movement of the meniscus when a flushing pulse is applied. FIG. 9C is a diagram illustrating the relationship between the flushing control data and the operation. FIG. 10A is a diagram illustrating a drive signal used for a weak flushing operation. FIG. 10B is a diagram illustrating the movement of the meniscus when a flushing pulse is applied. FIG. 10C is a diagram for explaining the relationship between the flushing control data and the operation. It is a figure for demonstrating operation | movement of 2nd Embodiment. FIG. 12A is a diagram illustrating a flushing pulse group applied to the piezo element in the second embodiment. FIG. 12B is a diagram for explaining the contents of the operation. It is a figure explaining the drive signal generation circuit of 3rd Embodiment, and a peripheral part. FIG. 14A is a diagram illustrating a first drive signal and a second drive signal generated in the third embodiment. FIG. 14B is a diagram for explaining the contents of the operation. It is a figure explaining the relationship between the number of printed sheets and flushing operation | movement. It is a figure explaining the example of a combination of the liquid which performs strong flushing operation | movement, and the liquid which performs weak flushing.

  At least the following will be made clear by the description of the present specification and the accompanying drawings.

That is, a head for discharging the first liquid from a part of the plurality of nozzles and discharging a second liquid of a different type from the first liquid from the other part of the plurality of nozzles, and controlling the head An ejection control unit that performs a flushing operation for ejecting the liquid from the nozzle so as not to land on an object, wherein the amount of the second liquid ejected by the flushing operation is ejected by the flushing operation It will be clarified that a liquid discharge apparatus having a discharge control unit that controls the head so as to be different from the amount of the first liquid can be realized.
According to such a liquid discharge apparatus, the flushing operation is performed with a discharge amount suitable for the type of liquid. For this reason, useless consumption of the liquid can be suppressed.

In this liquid discharge apparatus, the second liquid has a smaller increase in viscosity with respect to the standing time than the first liquid, and the discharge control unit determines that the amount of the second liquid discharged in the flushing operation is It is preferable to control the head so that the amount of the first liquid ejected in the flushing operation is smaller.
According to such a liquid ejecting apparatus, it is possible to suppress a problem that the second liquid whose viscosity is difficult to increase is excessively consumed by the flushing operation.

In this liquid ejection apparatus, the head communicates with the nozzles, operates in a pressure chamber provided for each of the nozzles, and ejects liquid according to an applied ejection pulse. An element that applies a pressure change to the liquid, and the discharge control unit generates a drive signal that includes a plurality of the discharge pulses in a repetition cycle repeatedly for each repetition cycle; and the drive signal It is preferable to include an application control unit that selects necessary ones of a plurality of included discharge pulses for each of the repetition periods in accordance with the amount of liquid to be discharged and applies the same to the element.
According to such a liquid discharge apparatus, the liquid discharge amount in the flushing operation can be finely controlled.

In this liquid ejection apparatus, the head communicates with the nozzles, operates in a pressure chamber provided for each of the nozzles, and ejects liquid according to an applied ejection pulse. An element that gives a change in pressure to the liquid, and the discharge controller generates a drive signal that repeatedly includes a drive pulse group including a plurality of discharge pulses, and the amount of liquid to be discharged And an application control unit that determines the number of times of application of the ejection pulse group to the element.
According to such a liquid ejection apparatus, the liquid ejection amount can be determined by easy control.

In this liquid ejection apparatus, the head communicates with the nozzles, operates in a pressure chamber provided for each of the nozzles, and ejects liquid according to an applied ejection pulse. An element that applies a pressure change to the liquid, and the discharge control unit includes a first drive signal that includes a plurality of first discharge pulses that are applied to the element to discharge a predetermined amount of liquid within a repetition period. A first drive signal generation unit that repeatedly generates each repetition cycle, and a second discharge pulse that discharges a predetermined amount of liquid different from the predetermined amount by being applied to the element within the repetition cycle A second drive signal generating unit that repeatedly generates a plurality of second drive signals for each repetition period, and selecting and responding to the first drive signal and the second drive signal according to the amount of liquid to be ejected Mark It is preferred to have a application controller for.
According to such a liquid ejecting apparatus, fine control can be performed because each drive signal is dedicated.

In such a liquid ejection device, the drive signal generation unit generates a subsequent ejection pulse following the preceding ejection pulse, and an ejection amount accompanying application of the subsequent ejection pulse to the element is: It is preferable that the generation of the subsequent ejection pulse is started at a timing that is greater than the ejection amount determined according to the voltage waveform of the subsequent ejection pulse.
According to such a liquid ejection apparatus, it is possible to increase the liquid ejection efficiency.

In such a liquid ejection device, the ejection control unit periodically performs the flushing operation, and according to the liquid ejection amount in the period from the end of the previous flushing operation to the flushing operation performed this time, It is preferable to adjust the amount of liquid discharged in the flushing operation.
According to such a liquid discharge apparatus, the liquid discharge amount can be further optimized.

It is also clarified that the following control method of the liquid ejection apparatus can be realized.
In other words, the first liquid is ejected from a part of the plurality of nozzles, and the second liquid of a different type from the first liquid is ejected from the other part of the plurality of nozzles. A control method of a liquid ejection apparatus that performs a flushing operation for ejecting the first liquid and the second liquid from the nozzle so as not to cause a discharge amount of the second liquid in the flushing operation. It is also clarified that it is possible to realize a control method of the liquid ejection apparatus that controls the head so as to be different from the amount of the first liquid.

=== First Embodiment ===
<About the printing system>
The printing system illustrated in FIG. 1 includes a printer 1 and a computer CP. The printer 1 corresponds to a liquid ejecting apparatus, and ejects ink, which is a kind of liquid, toward a medium such as paper, cloth, or film. The medium is an object to which liquid is ejected. The computer CP is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer CP transmits print data corresponding to the image to the printer 1.

=== Overview of Printer 1 ===
<About the overall configuration>
The printer 1 includes a paper transport mechanism 10, a carriage movement mechanism 20, a head unit 30, a drive signal generation circuit 40, a detector group 50, and a main control unit 60.

  The paper transport mechanism 10 is a mechanism for transporting the paper S in the transport direction. As shown in FIG. 2, the paper transport mechanism 10 includes a platen 11 that supports the paper S from the back surface side, a transport roller 12 that is disposed upstream of the platen 11 in the transport direction, and a downstream side of the platen 11 in the transport direction. The paper discharge roller 13 is disposed, and a transport motor 14 serving as a drive source for the transport roller 12 and the paper discharge roller 13 is provided.

  The carriage movement mechanism 20 is a mechanism for moving the carriage CR in the carriage movement direction. The carriage CR is a member to which the ink cartridge IC and the head HD are attached. The head HD is attached to the carriage CR so as to face the platen 11. The carriage moving mechanism 20 includes a timing belt 21, a carriage motor 22, and a guide shaft 23. The timing belt 21 is connected to the carriage CR and is spanned between the drive pulley 24 and the idler pulley 25. The carriage motor 22 is a drive source that rotates the drive pulley 24. The guide shaft 23 is a member for guiding the carriage CR in the carriage movement direction. In the carriage moving mechanism 20, the carriage CR can be moved in the carriage movement direction by operating the carriage motor 22.

  A cap member CP for receiving ink is provided at the home position of the carriage CR. As shown in FIG. 3, the cap member CP faces the nozzle surface of the head HD when the carriage CR is positioned at the home position, and receives ink ejected from the head HD. Further, at the time of standby for a long time, the cap member CP is in contact with the nozzle surface so that each nozzle faces the inner space.

  The head unit 30 includes a head HD and a head controller HC. The head HD is a kind of liquid ejection head, and ejects ink toward the paper S. The head controller HC controls the head HD based on the head control signal from the main controller 60.

  The drive signal generation circuit 40 is a kind of drive signal generation unit, and generates a drive signal COM. The drive signal COM is applied to the head HD (piezo element 34, see FIG. 4) when printing on the paper S. As shown in an example in FIG. 7, the ejection pulse (small dot pulse SP, first dot) is applied. A series of signals including a medium dot pulse MP1 and a second medium dot pulse MP2). Here, the ejection pulse is a voltage change pattern that causes the piezo element 34 to perform a predetermined operation in order to eject droplet-like ink from the head HD. Since the drive signal COM includes an ejection pulse, the drive signal generation circuit 40 can also be referred to as an ejection pulse generation unit. The configuration of the drive signal generation circuit 40 and the ejection pulse will be described later.

The detector group 50 includes a plurality of detectors that monitor the status of the printer 1. This detector includes a linear encoder 51 that changes the output level of the signal every time the carriage CR moves a predetermined distance. The output from the linear encoder 51 is used when the generation start timing of the drive signal COM (the start of the repetition period T) is determined. Then, the detection result by each detector is output to the main controller 60.
The main control unit 60 performs overall control in the printer 1. The main controller 60 will also be described later.

<About Head HD>
FIG. 4 is a cross-sectional view of the head HD. The head HD has a plurality of a series of flow paths corresponding to the nozzles Nz from the common ink chamber 31 through the supply side communication port 32 and the pressure chamber 33 to the nozzles Nz. When the printer 1 is used, this flow path is filled with ink. The volume of the pressure chamber 33 is changed by the operation of the piezo element 34. That is, a part of the pressure chamber 33 is partitioned by the diaphragm, and the piezoelectric element 34 is provided on the surface of the diaphragm opposite to the pressure chamber 33.

  A plurality of piezo elements 34 are provided corresponding to the respective pressure chambers 33. In other words, a plurality of nozzles corresponding to the nozzles Nz are provided. The piezo element 34 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 raised, the piezoelectric body is charged, and accordingly, the piezo element 34 is bent (that is, deformed) so as to protrude toward the pressure chamber 33 side. As a result, the pressure chamber 33 is contracted. The higher the degree of charge, the greater the amount of deflection of the piezo element 34, causing the pressure chamber 33 to contract significantly. The deformation amount of the piezo element 34 is determined by the application portion (for example, ejection pulse) in the drive signal COM. Therefore, it can be said that the piezo element 34 is deformed according to the voltage of the applied drive signal COM.

  Thus, the piezo element 34 is an element that operates to discharge ink by charging and discharging, and corresponds to an element that contracts the volume of the pressure chamber 33 by charging. When the volume of the pressure chamber 33 changes due to the deformation of the piezo element 34, the pressure in the ink in the pressure chamber 33 changes. Since the nozzle Nz communicates with the pressure chamber 33, ink droplets can be ejected from the nozzle Nz due to a pressure change caused by ink in the pressure chamber 33. Then, the amount of ink droplets can be adjusted depending on how the pressure change is applied, and the meniscus (the free surface of the ink exposed at the nozzle Nz) can be moved within the nozzle Nz to such an extent that ink is not ejected.

<About nozzle row>
FIG. 5 is a diagram illustrating nozzle rows provided on the nozzle plate 35 of the head HD. As shown in FIG. 5, the nozzle plate 35 is provided with a plurality of nozzles Nz to form a nozzle group. These nozzles Nz are grouped for each type of ink to be ejected, and four nozzle rows are configured by each group. With this head HD, four types of ink can be ejected. Specifically, the leftmost nozzle row Nk in FIG. 5 ejects black ink. The nozzle row Nc located second from the left ejects cyan ink. Similarly, the nozzle row Nm located third from the left ejects magenta ink, and the nozzle row Ny located rightmost ejects yellow ink. One nozzle row is composed of 96 to 180 nozzles Nz arranged at a constant interval in the transport direction of the paper S. Four nozzle rows are provided in the carriage movement direction orthogonal to the transport direction.

<Main controller 60>
The main control unit 60 performs overall control in the printer 1. For example, the control target unit is controlled based on print data received from the computer CP and detection results from each detector, and an image is printed on the paper S. As shown in FIG. 1, the main control unit 60 includes an interface unit 61, a CPU 62, and a memory 63. The interface unit 61 exchanges data with the computer CP. The CPU 62 performs overall control of the printer 1. The memory 63 secures an area for storing a computer program, a work area, and the like. 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 10 and the carriage movement mechanism 20. Further, the CPU 62 transmits a head control signal for controlling the operation of the head HD to the head controller HC, and transmits a control signal for generating the drive signal COM to the drive signal generation circuit 40. A control signal for generating the drive signal COM is also called DAC data, and is, for example, digital data of a plurality of bits. This DAC data defines the voltage change pattern of the generated drive signal COM. Therefore, the DAC data can be said to be data indicating the voltage of the drive signal COM and the ejection pulse. The DAC data is stored in a predetermined area of the memory 63, and is read out when the drive signal COM is generated and output to the drive signal generation circuit 40.

<About the drive signal generation circuit 40>
The drive signal generation circuit 40 functions as a drive signal generation unit, and generates a drive signal COM having ejection pulses MP1, MP2, SP and a fine vibration pulse VP based on the DAC data. As illustrated in FIG. 6, the drive signal generation circuit 40 includes a DAC circuit 41, a voltage amplification circuit 42, and a current amplification circuit 43. The DAC circuit 41 converts digital DAC data into an analog signal. The voltage amplification circuit 42 amplifies the voltage of the analog signal converted by the DAC circuit 41 to a level at which the piezo element 34 can be driven. In the printer 1, the analog signal output from the DAC circuit 41 is 3.3 V at maximum, whereas the amplified analog signal (also referred to as a waveform signal for convenience) output from the voltage amplifier circuit 42 is 42 V at maximum. It is. The current amplifying circuit 43 amplifies the current of the waveform signal from the voltage amplifying circuit 42 and outputs it as a drive signal COM. The current amplifying circuit 43 is configured by, for example, a push-pull connected transistor pair.

<About the head controller HC>
The head control unit HC selects a necessary portion of the drive signal COM generated by the drive signal generation circuit 40 based on the head control signal from the main control unit 60 and applies it to the piezo element 34. For this reason, as shown in FIG. 6, the head controller HC includes a plurality of switches 36 provided for each piezo element 34 in the middle of the supply line of the drive signal COM. Then, the head controller HC generates a switch control signal SW from the head control signal. By controlling each switch 36 by this switch control signal SW, a necessary portion (for example, ejection pulses MP1, MP2, SP) of the drive signal COM is applied to the piezo element 34. At this time, the ejection of ink from the nozzles Nz can be controlled depending on how to select the necessary portions.

<About the drive signal COM>
Next, the drive signal COM generated by the drive signal generation circuit 40 will be described. The drive signal COM shown in FIG. 7 can be divided into a first half portion corresponding to the period T1 and a second half portion corresponding to the period T2, with reference to the rising edge of the latch signal LAT. The first half is the front unit periodic signal, and the second half is the rear unit periodic signal. The front unit period signal and the rear unit period signal are generated over a unit period defined by one dot. In other words, it can be said that the drive signal COM includes two unit period signals generated over the unit periods T1 and T2 defined by the dot gradation in the repetition period T. Then, the drive signal generation circuit 40 repeatedly generates the drive signal COM every repetition period T. These front-side unit periodic signal and rear-side unit periodic signal are different in included pulses. That is, the front unit cycle signal includes three ejection pulses including a first medium dot pulse MP1, a small dot pulse SP, and a second medium dot pulse MP2. On the other hand, the rear unit periodic signal includes a minute vibration pulse VP in addition to these three ejection pulses.

  Among these pulses, the micro-vibration pulse VP is for suppressing the increase in the viscosity of the ink in the nozzle Nz, and when no ink droplet is ejected from the nozzle Nz, to the piezo element 34 corresponding to the nozzle Nz. Applied. The small dot pulse SP is for ejecting an amount (small amount) of ink droplets suitable for forming small dots from the nozzle Nz. That is, when an ink droplet is ejected to form a small dot, it is applied to the piezo element 34 corresponding to the nozzle Nz. The first medium dot pulse MP1 is for ejecting an amount (medium amount) of ink suitable for forming a medium dot from the nozzle Nz. The first medium dot pulse MP1 is used when forming a medium dot and when forming a large dot. The second medium dot pulse MP2 is also for ejecting an amount of ink suitable for forming a medium dot from the nozzle Nz. The second medium dot pulse MP2 is used in combination with the first medium dot pulse MP1 when a large dot is formed.

<About printing operation>
Next, a printing operation in this printing system will be described. In this printing system, the printer 1 performs a printing operation based on the print data transmitted from the computer CP to the printer 1. In the printing operation by the printer 1, the dot formation process and the paper transport process are repeatedly performed. The dot forming process is a process of forming dots on the paper S by discharging ink droplets from the nozzles Nz of the head HD while moving the carriage CR in the carriage moving direction, and corresponds to a liquid moving and discharging operation. The paper transport process is a process of moving the paper S in the transport direction by an amount determined by the nozzle pitch, the number of nozzles, and the like, and corresponds to a medium transport process. By performing the paper transport process, it is possible to form dots in the subsequent dot formation process for the portion on the paper S where the dots are not formed. In the printer 1, a plurality of dots having different sizes can be formed in the dot formation process. That is, three types of dots consisting of small dots, medium dots, and large dots can be formed. Further, since it is possible to select a dot without forming a dot, it is possible to control four gradations.

  As shown in FIGS. 8A and 8B, no dot corresponds to dot formation data (SI data) [00], and small dot formation corresponds to dot formation data [01]. Similarly, formation of medium dots corresponds to dot formation data [10], and formation of large dots corresponds to dot formation data [11]. This dot formation data is given based on the head control signal, and can be said to be information indicating the amount of ink ejected from the nozzle Nz. In FIG. 8B, flushing control data is described in addition to the dot formation data. This flushing control data indicates the contents of the flushing operation. In the printing operation, the flushing control data is defined in data [00]. As a result, the flushing operation is not performed, and ink droplet ejection control is performed based on the dot formation data. Other data will be described later.

  When the dot formation data [11] is given, the head controller HC controls the switch 36 so that the fine vibration pulse VP is applied to the piezo element 34. In the example of FIG. 8A, the switch 36 is turned on over a period T21 in order to apply the minute vibration pulse VP included in the rear unit periodic signal. In this case, the head controller HC sets the switch control signal SW to the H level over the period T21. The front unit period signal does not include the fine vibration pulse VP. For this reason, even if the dot formation data [00] is given, the drive signal COM is not applied to the piezo element 34.

  When the dot formation data [01] is given, the head controller HC controls the switch 36 so that the small dot pulse SP is applied to the piezo element 34. In the example of FIG. 8A, the switch 36 is turned on over a period T12 in order to apply the small dot pulse SP included in the front unit periodic signal. In this case, the head controller HC sets the switch control signal SW to the H level over the period T12. When applying the small dot pulse SP included in the rear unit periodic signal, the head controller HC sets the switch control signal SW to the H level over the period T23.

  When the dot formation data [10] is given, the head controller HC controls the switch 36 so that the first medium dot pulse MP1 is applied to the piezo element 34. In the example of FIG. 8A, the head controller HC sets the switch control signal SW to the H level over the period T11 in order to apply the first medium dot pulse MP1 included in the front unit period signal. When applying the first medium dot pulse MP1 included in the rear unit periodic signal, the head controller HC sets the switch control signal SW to the H level over the period T22.

  When the dot formation data [11] is given, the head controller HC controls the switch 36 so that the first medium dot pulse MP1 and the second medium dot pulse MP2 are applied to the piezo element 34. In the example of FIG. 8A, in order to apply the first medium dot pulse MP1 and the second medium dot pulse MP2 included in the rear unit periodic signal, the head controller HC switches the switch control signal SW over the period T22 and the period T24. To H level. When applying the first medium dot pulse MP1 and the second medium dot pulse MP2 included in the rear unit period signal, the head controller HC sets the switch control signal SW to the H level over the periods T11 and T13. To do.

  In the dot formation process, the main control unit 60 outputs a DAC signal to the drive signal generation circuit 40. The drive signal generation circuit 40 generates a drive signal COM having a voltage corresponding to the DAC signal. Therefore, the main control unit 60 corresponds to the generation control unit for controlling the drive signal generation circuit 40 to generate the drive signal COM. Further, the main control unit 60 outputs a head control signal to the head control unit HC. The head controller HC controls the switch 36 according to the head control signal, and applies a necessary portion of the drive signal COM to the piezo element 34. For this reason, the set of the main control unit 60 and the head control unit HC determines the necessary one of the ejection pulse and the fine vibration pulse VP included in the drive signal COM according to dot formation data which is information indicating the ink ejection amount. It corresponds to an application control unit that selects and applies to the piezo element 34. In addition, the set of the main control unit 60, the drive signal generation circuit 40, and the head control unit HC corresponds to an ejection control unit that controls the head HD in order to eject ink droplets from the nozzles Nz.

  As described above, in the printing operation, the dot formation process and the paper conveyance process are repeatedly performed. However, the viscosity of the ink in the nozzle Nz may increase depending on the ejection frequency of the ink droplets. A flushing operation is performed to discharge such thickened ink. The flushing operation is performed by causing the cap member CP provided at the home position to eject ink regardless of the dot formation data. Here, the cap member CP is positioned outside the platen 11 that supports the paper S in the carriage movement direction. In other words, it is arranged at a position outside the paper S that is the object. For this reason, the flushing operation can be said to be an operation of discharging the liquid from the nozzle Nz so as not to land on the object. The flushing operation is performed periodically. For example, it is performed after a predetermined time has elapsed from the previous flushing operation and at the timing when the first dot formation operation is completed.

=== About Flushing Operation ===
Conventionally, conditions for flushing have been determined according to a liquid that tends to thicken from the viewpoint of preventing ejection failure of ink droplets. For this reason, when multiple types of ink with different easiness of thickening are ejected from the same head HD, the flushing operation is excessively performed on the ink that is difficult to thicken, and the ink is consumed wastefully. There was a problem of being. For example, in dye-based ink, color ink (a type of second liquid) has a characteristic that the degree of increase in viscosity with respect to the standing time is smaller than that of black ink (a type of first liquid). That is, it has the characteristic that it is hard to thicken. For this reason, when the flushing operation is performed under the same conditions as the black ink, there is a problem that the ink is wasted. Therefore, in this printer, the set (discharge control unit) of the main control unit 60, the drive signal generation circuit 40, and the head control unit HC discharges the amount of color ink discharged in the flushing operation. The head HD is controlled so as to be smaller than the amount of black ink. Details will be described below.

<About the drive signal COM>
First, the drive signal COM used for the flushing operation will be described. The driving signal COM for the flushing operation shown in FIG. 9A can also be divided into a first half portion corresponding to the period T1 and a second half portion corresponding to the period T2. The first half is the front unit periodic signal, and the second half is the rear unit periodic signal. The drive signal generation circuit 40 repeatedly generates this drive signal COM every repetition period T. Unlike the drive signal COM for printing operation described with reference to FIG. 7, the front unit period signal and the rear unit period signal include the same pulses. That is, the front unit period signal includes four flushing ejection pulses (hereinafter also referred to as flushing pulses FP). The rear unit periodic signal also includes four flushing pulses FP. Each flushing pulse FP has the same waveform. Since this waveform defines the operation of the piezo element 34, the piezo element 34 is similarly deformed regardless of which flushing pulse FP is applied. Due to the deformation of the piezo element 34, a change in pressure occurs in the ink in the pressure chamber 33, and an ink droplet is ejected from the nozzle Nz.

  FIG. 9B is a diagram for explaining the movement of the meniscus during the flushing operation. In FIG. 9B, the vertical axis indicates the meniscus state by the amount of ink, and the horizontal axis indicates time. Regarding the vertical axis, 0 ng indicates the position of the meniscus in the steady state. As the value increases toward the positive side, the meniscus is pushed out in the ejection direction. On the other hand, the larger the value on the negative side, the more the meniscus is drawn to the pressure chamber 33 side. The contents of the vertical axis and horizontal axis similarly apply to the vertical axis and horizontal axis of FIG. 10B. The solid lines in FIGS. 9B and 10B indicate the state of the meniscus when one flushing pulse FP is applied to the piezo element 34. The alternate long and short dash line indicates the state of the meniscus when two flushing pulses FP are continuously applied to the piezo element 34 at intervals of the drive signal COM. Here, the position of the meniscus changes according to the ink pressure in the pressure chamber 33. Therefore, it can be said that the meniscus position indicates the ink pressure in the pressure chamber 33.

  As shown by the solid line in FIG. 9B, when one flushing pulse FP is applied to the piezo element 34, an amount of ink droplets corresponding to the voltage waveform of the flushing pulse FP is ejected. Briefly, when the flushing pulse FP is applied, the meniscus drawn in the direction of the pressure chamber 33 (− side) is strongly pushed out in the ejection direction (+ side), and ink droplets are ejected from the nozzle Nz. . Note that the vertex on the + side of the solid line indicates the ejection amount of the ink droplet. When the ink droplet is ejected, the meniscus returns to the direction of the pressure chamber 33 by the reaction. Since the pressure chamber 33 expands at this timing, the return force of the meniscus is relieved, and the amplitude of the residual meniscus vibration (ink pressure vibration) thereafter can be suppressed. By continuously applying the flushing pulse FP to the piezo element, the thickened ink in the nozzle is discharged.

<About flushing action (strong)>
In this printer, the amount of ink discharged at the time of flushing is varied according to the type of ink. Regarding the degree of increase in viscosity with respect to the standing time, the degree of increase in black ink is greater than the degree of increase in color ink. For this reason, with black ink, the amount of ink discharged is increased compared with color ink, and the effect of the flushing operation is enhanced.

  In the flushing operation for the black ink, the main control unit 60 and the head control unit HC (application control unit) apply all the flushing pulses FP included in each unit periodic signal to the piezo element 34. Thereby, each time the respective flushing pulse FP is applied, an ink droplet is ejected from the nozzle Nz, and the thickened ink is efficiently discharged. In order to perform such control, the switch control signal SW is at the H level in all periods. In the head controller HC, the flushing control data is data [10], and the flushing operation is performed regardless of the contents of the dot formation data.

  Here, the main control unit 60 and the drive signal generation circuit 40 determine that the amount of ink droplets ejected by a flushing pulse FP (corresponding to a subsequent ejection pulse) to be applied to the piezo element 34 later is the flushing pulse FP. The interval between the front and rear flushing pulses FP is determined so as to be larger than the amount of ink droplets determined by the voltage waveform. As shown in FIG. 9B, when an ink droplet is ejected by the flushing pulse FP (corresponding to the preceding ejection pulse) previously applied to the piezo element 34, pressure vibration remains in the ink in the pressure chamber 33. . In the printer 1, the amount of ink droplets ejected by the subsequent flushing pulse FP is increased by using the pressure vibration generated by the previous flushing pulse FP. As described above, when the flushing pulse FP is applied, the meniscus is first drawn toward the pressure chamber 33. Therefore, the subsequent flushing pulse FP is applied to the piezo element 34 in accordance with the timing at which the meniscus is drawn by the residual vibration. As a result, the meniscus can be drawn larger than that drawn only by the flushing pulse FP, and the meniscus amplitude can be increased. As a result, the ejection amount of the ink droplet can be increased more than the ejection amount defined by the waveform of the flushing pulse FP. In FIG. 9B, the discharge amount can be increased by ΔV. As a result, it is possible to increase the removal efficiency of the thickened ink by the flushing operation.

  The main control unit 60 and the drive signal generation circuit 40 (drive signal generation unit) that perform such control have a discharge amount according to the application of the subsequent discharge pulse to the element in accordance with the voltage waveform of the subsequent discharge pulse. It can be said that the generation of the trailing ejection pulse is started at a timing when the ejection amount becomes larger than the fixed ejection amount.

<About flushing operation (weak)>
As described above, regarding the degree of increase in the viscosity with respect to the standing time, the increase degree of the color ink is smaller than the increase degree of the black ink. For this reason, for the color ink, the ink discharge amount is reduced as compared with the black ink, and the effect of the flushing operation is weaker than that of the black ink.

  As shown in FIG. 10A, in the flushing operation for the color ink, the main control unit 60 and the head control unit HC (application control unit) select every other plurality of flushing pulses FP included in each unit period signal. Applied to the piezo element 34. As a result, ink droplets are ejected at longer intervals than during the black ink flushing operation. As a result, a flushing operation suitable for increasing the viscosity of the color ink can be performed. In order to perform such control, the main control unit 60 and the head control unit HC switch the signal level of the switch control signal SW between the H level and the L level for each period. Further, as shown in FIG. 10C, the head control unit HC sets the flushing control data to data [01], and performs this flushing operation regardless of the contents of the dot formation data (SI data). As shown in FIG. 10B, in this flushing operation, since every other flushing pulse FP is applied to the piezo element 34, the amount of ink droplets ejected by each flushing pulse FP becomes substantially equal. . This is because the residual vibration of ink is not used.

<Summary>
As described above, in the first embodiment, the flushing operation is performed with different ejection amounts for the black ink and the color ink having different viscosity increasing degrees with respect to the standing time. For this reason, the discharge amount can be optimized. As a result, it is possible to suppress the problem that the ink is consumed wastefully.

  In addition, for the color ink, which has a smaller increase in viscosity with respect to the standing time than the black ink, the discharge amount during the flushing operation is made smaller than the discharge amount of the black ink. For this reason, the malfunction that color ink is consumed excessively can be suppressed.

  Further, during the color ink flushing operation, a necessary amount is selected from the group of flushing pulses FP included in the drive signal COM and applied to the piezo element 34, so that the ejection amount can be finely controlled. For example, the ejection amount can be changed by changing the flushing pulse FP to be selected.

  Further, since the interval between the front and rear flushing pulses FP is determined so that the ejection amount is larger than the ejection amount determined by the voltage waveform of the flushing pulse FP during the flushing operation of the black ink, the flushing efficiency can be improved.

=== Second Embodiment ===
In the first embodiment described above, during the color ink flushing operation, by selecting some flushing pulses FP included in the front unit period signal and the rear unit period signal, the discharge amount of the color ink is reduced. The discharge amount was set lower than the discharge amount. In this regard, the ink discharge amount may be adjusted based on the unit cycle signal. For example, each unit period shown in FIG. 9A has four flushing pulses FP. The main control unit 60 and the head control unit HC (application control unit) perform the control of the switch 36 for each unit periodic signal, so that the flushing pulse group including these flushing pulses FP is sent to the piezo element 34 as a unit. Is controlled.

  11 and 12 are diagrams for explaining an example of this control. FIG. 11 shows the relationship between the number of flushing times and the number of unit periodic signals applied to the piezo element 34 for black ink and color ink. In FIG. 11, the number of unit period signals is represented by a segment (seg). This is because each unit period signal constitutes a part of the drive signal COM. FIG. 12A shows a signal applied to the piezo element 34 when operating at 256 seg. FIG. 12B shows the contents of the flushing control data used at that time.

  In the second embodiment, the main control unit 60 and the drive signal generation circuit 40 (drive signal generation unit) generate the same drive signal COM as in the first embodiment. Then, as shown in FIG. 11, the main control unit 60 and the head control unit HC (application control unit) perform a flushing operation at 512 seg for the black ink from the first time. This is because the flushing conditions are determined based on the black ink having the largest degree of increase in viscosity with respect to the standing time. Further, the main control unit 60 and the head control unit HC perform a flushing operation at 256 seg for the odd number of times and a flushing operation at 100 seg for the even number of times. In the flushing operation at 256 seg, as shown in FIG. 12A, the front unit periodic signal is not applied to the piezo element 34, and the rear unit periodic signal is applied to the piezo element 34. In this case, as shown in FIG. 12B, the head controller HC sets the dot formation data [00] and the flushing control data [00] over the period T1. In addition, the flushing control data [10] is used over the period T2. As a result, the rear unit periodic signal is applied to the piezo element 34 regardless of the content of the dot formation data. This data is an example. Further, in the flushing operation at 100 seg, the ratio between application and non-application of the unit period signal may be changed.

  In the second embodiment, the main controller 60 and the head controller HC (application controller) determine the number of times the flushing pulse group is applied according to the amount of liquid to be ejected. For this reason, the ink discharge amount can be determined by simple control.

=== Third Embodiment ===
In each of the embodiments described above, the main controller 60 and the drive signal generation circuit 40 generate one type of drive signal COM for the flushing operation. Here, a plurality of types of drive signals COM for the flushing operation may be generated. Hereinafter, the third embodiment configured as described above will be described. In the printer 1 of the third embodiment, the configuration of the drive signal generation circuit 40 and the configuration of the head control unit HC are different from those of the above-described embodiments. Hereinafter, the third embodiment will be described focusing on the differences.

  FIG. 13 is a diagram for explaining the third embodiment, and is a block diagram for explaining the configuration of the drive signal generation circuit 40 and its peripheral part. The printer 1 includes a first drive signal generation circuit 40A and a second drive signal generation circuit 40B. The first drive signal generation circuit 40A generates the first drive signal COM based on the first DAC data output from the main control unit 60. The second drive signal generation circuit 40B generates the second drive signal COM based on the second DAC data output from the main control unit 60.

  The first drive signal generation circuit 40A and the second drive signal generation circuit 40B are configured similarly to the drive signal generation circuit 40 of the first embodiment. That is, the first drive signal generation circuit 40A includes a first DAC circuit 41A, a first voltage amplification circuit 42A, and a first current amplification circuit 43A. The second drive signal generation circuit 40B includes a second DAC circuit 41B, a second voltage amplification circuit 42B, and a second current amplification circuit 43B. Description of each of these parts is omitted.

  The head controller HC includes a first switch 36A for the first drive signal COM and a second switch 36B for the second drive signal COM. A plurality of these first switches 36 </ b> A and second switches 36 </ b> B are provided in pairs for each piezo element 34. Then, the head controller HC individually generates switch control signals SW1 and SW2 for the switches 36A and 36B. That is, the first switch control signal SW1 for the first switch 36A and the second switch control signal SW2 for the second switch 36B are generated. By these switch control signals SW1 and SW2, necessary portions of the first drive signal COM and the second drive signal COM are applied to the piezo element 34.

  FIG. 14A is a diagram for explaining the first drive signal COM_A and the second drive signal COM_B generated by the drive signal generation circuit 40. FIG. 14B is a diagram illustrating the relationship between each drive signal COM_A, COM_B and ink. The first drive signal COM_A is the same as that described in the first embodiment. That is, each of the front unit period signal and the rear unit period signal includes four first flushing pulses FP1. The voltage waveform of the second drive signal COM_B is determined so that the ink ejection amount is smaller than that of the first drive signal COM_A. That is, each of the front unit period signal and the rear unit period signal includes three second flushing pulses FP2 having a smaller ejection amount than the first flushing pulse FP1. In the second flushing pulse FP2, the difference Vh2 from the highest voltage to the lowest voltage is smaller than the difference Vh1 from the highest voltage to the lowest voltage in the first flushing pulse FP1. Further, regarding the slope of the portion that changes from the lowest voltage to the highest voltage, the slope in the second flushing pulse FP2 is smaller than the slope in the first flushing pulse FP1. That is, the amount of voltage change per unit time is small. As a result, the ink droplet ejection amount is reduced.

  In this embodiment, a flushing operation is performed using the first drive signal COM_A having a high viscosity ink discharge capability for the black ink that tends to thicken, and the first drive is performed for the color ink that is harder to thicken than the black ink. The flushing operation is performed using the second drive signal COM_B having a smaller discharge amount than the signal COM_A. As described above, the discharge amount of the color ink during the flushing operation can be made smaller than the discharge amount of the black ink, and the problem that the ink is consumed wastefully can be suppressed.

  In particular, since each drive signal COM is dedicated in the third embodiment, even if the drive signal COM used to eject a plurality of types of ink is generated by one drive signal generation unit, these inks are used. There is an advantage that flushing can be performed under different conditions.

=== About Other Embodiments ===
The above-described embodiment is mainly described with respect to a printing system having the printer 1 as a liquid ejecting apparatus, and includes a liquid ejecting method, a liquid ejecting system, a method for setting a flushing pulse FP, and driving of a head HD. The disclosure includes a device, a driving method of the head HD, a computer program, a storage medium readable by the computer CP, and the like. Further, this embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<Relationship with the number of printed sheets>
In each of the above-described embodiments, the flushing operation is periodically performed. Here, the number of printed sheets (number of ink ejections) during the period from the previous flushing operation to the current flushing operation may vary depending on the print data.
In this case, the smaller the number of printed sheets, the more ink needs to be ejected in the flushing operation, and the ejection capacity needs to be recovered. Therefore, the amount of ink ejected in the flushing operation may be adjusted according to the number of printed sheets in the period from the end of the previous flushing operation to the flushing operation performed this time. For example, as shown in FIG. 15, when the number of printed sheets in the period until the flushing operation performed this time is five sheets of photographic paper, it is highly possible that the thickened ink remains, and the black ink is 512 seg. The flushing operation is performed at 256 seg for the color ink. Further, when the number of printed sheets is 10, assuming that there is no thickened ink remaining compared to the case of 5 sheets, the flushing operation at 384 seg for black ink and the flushing operation at 128 seg for color ink are performed. .
With this configuration, the ink discharge amount can be optimized.

<About the first liquid and the second liquid>
In the above-described embodiments, the dye black ink is exemplified as the first liquid and the dye color ink is exemplified as the second liquid. However, the present invention is not limited to this combination. In short, any combination that has a difference in ease of thickening may be used. For example, as shown in FIG. 16, in the case of a combination of pigment ink and dye ink, the viscosity of the pigment ink is relatively easy to increase. In this case, the flushing operation (high) having a high recovery capability may be performed on the pigment ink, and the flushing operation (low) having a low recovery capability may be performed on the dye ink. If a combination of pigment black ink and pigment color ink is used, a flushing operation with high recovery capability (strong) is performed for pigment black ink and a low recovery capability is performed for pigment color ink. (Weak) may be performed. In addition, if the combination of the base liquid or coating liquid and the drawing ink (dye ink or pigment ink) is performed, the flushing operation (strong) with a high recovery ability is performed on the base liquid or coating liquid, and the drawing ink is applied. Thus, a flashing operation (weak) with a low recovery capability may be performed.

<About the number of drive signals>
In the above-described third embodiment, the case where the first drive signal COM_A and the second drive signal COM_B are generated has been described, but three or more types of drive signals may be generated.

<About the drive signal generator>
In each of the above-described embodiments, the drive signal generation circuit 40 including the DAC circuit 41, the voltage amplification circuit 42, and the like is exemplified as the drive signal generation unit, but the configuration is not limited thereto. For example, the waveform of the ejection pulse or the flushing pulse FP may be created by an analog circuit. In short, any circuit that can generate the ejection pulse and the flushing pulse FP may be used.

<Elements that operate to eject ink droplets>
In each of the above-described embodiments, the piezo element 34 is exemplified as an element that performs an operation for ejecting ink droplets. However, the present invention is not limited to this. For example, a heating element or an electrostatic actuator may be used.

<About other application examples>
In the above-described embodiment, the printer 1 has been described as 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 modeling machine, liquid vaporization apparatus, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied. These methods and manufacturing methods are also within the scope of application.

1 printer, 30 head unit, 33 pressure chamber, 34 piezo elements,
36 switch, 40 drive signal generation circuit, 40A first drive signal generation circuit,
40B second drive signal generation circuit, 60 main control unit, HD head,
Nz nozzle, HC head controller, COM drive signal,
COM_A first drive signal, COM_B second drive signal,
FP flushing pulse, FP1 first flushing pulse,
FP2 second flushing pulse, T repetition period,
SW switch control signal, SW1 first switch control signal,
SW1 First switch control signal

Claims (8)

A head for discharging the first liquid from a part of the plurality of nozzles and discharging a second liquid of a type different from the first liquid from the other part of the plurality of nozzles;
A discharge control unit for controlling the head to perform a flushing operation for discharging the liquid from the nozzle so as not to land on an object;
An ejection controller that controls the head such that the amount of the second liquid ejected in the flushing operation is different from the amount of the first liquid ejected in the flushing operation;
A liquid ejection apparatus having The second liquid is
The degree of increase in viscosity with respect to the standing time is smaller than that of the first liquid,
The discharge controller is
2. The liquid ejecting apparatus according to claim 1, wherein the head is controlled such that an amount of the second liquid ejected by the flushing operation is smaller than an amount of the first liquid ejected by the flushing operation. The head is
A pressure chamber communicated with the nozzle and provided for each nozzle;
An operation for discharging the liquid according to the applied discharge pulse, and an element for giving a pressure change to the liquid in the pressure chamber,
The discharge controller is
A drive signal generating unit that repeatedly generates a drive signal including a plurality of the ejection pulses in a repetition cycle for each repetition cycle;
An application control unit configured to select a required one of the plurality of ejection pulses included in the drive signal for each repetition period according to the amount of liquid to be ejected and to apply to the element. 3. The liquid ejection device according to 2. The head is
A pressure chamber communicated with the nozzle and provided for each nozzle;
An operation for discharging the liquid according to the applied discharge pulse, and an element for giving a pressure change to the liquid in the pressure chamber,
The discharge controller is
A drive signal generation unit that repeatedly generates a drive signal including an ejection pulse group including a plurality of ejection pulses;
The liquid ejecting apparatus according to claim 1, further comprising: an application control unit that determines the number of times the ejection pulse group is applied to the element in accordance with the amount of liquid ejected. The head is
A pressure chamber communicated with the nozzle and provided for each nozzle;
An operation for discharging the liquid according to the applied discharge pulse, and an element for giving a pressure change to the liquid in the pressure chamber,
The discharge controller is
A first drive signal generating section that repeatedly generates a first drive signal that includes a plurality of first discharge pulses that are applied to the element to discharge a predetermined amount of liquid within a repetition cycle;
A second drive signal is generated repeatedly at each repetition period, the second drive signal including a plurality of second ejection pulses within a repetition period for discharging a predetermined amount of liquid different from the predetermined amount by being applied to the element. Two drive signal generators;
3. The liquid ejection apparatus according to claim 1, further comprising an application control unit that selects and applies the first drive signal and the second drive signal to corresponding elements in accordance with an amount of liquid to be ejected. The drive signal generator is
A subsequent discharge pulse is generated following the preceding discharge pulse, and the discharge amount accompanying application of the subsequent discharge pulse to the element is determined by a discharge amount determined according to the voltage waveform of the subsequent discharge pulse. 6. The liquid ejection apparatus according to claim 1, wherein generation of the subsequent ejection pulse is started at a timing when the number of the subsequent ejection pulses increases. The discharge controller is
The flushing operation is performed periodically, and the amount of liquid ejected in the flushing operation is adjusted according to the liquid ejection amount in a period from the end of the previous flushing operation to the current flushing operation. Item 6. The liquid ejection device according to any one of Items 1 to 5. A head for discharging the first liquid from a part of the plurality of nozzles and discharging a second liquid of a different type from the first liquid from the other part of the plurality of nozzles so as not to land on the object; A control method of a liquid ejection apparatus that performs a flushing operation for ejecting the first liquid and the second liquid from the nozzle.
A method for controlling a liquid ejection apparatus, wherein the head is controlled such that an ejection amount of the second liquid in the flushing operation is different from an amount of the first liquid in the flushing operation.

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