JP2015003495A - Droplet ejection device and nozzle recovery method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively eliminate solid particle settling in ink for enabling ink droplets to be stably ejected for a long time.SOLUTION: A droplet ejection device comprises: a head 1 including an ink chamber, a nozzle 12 corresponding to the ink chamber, and energy application means applying a driving pulse to drive so as to apply energy to ink in the ink chamber, which ejects ink droplets from the nozzle 12 to perform printing on a print region of a recording material C; and driving pulse generation means which generates as the driving pulse an ejection pulse ejecting ink droplets from the nozzle 12, and a micro-vibration pulse applying micro-vibration to ink in the ink chamber so that the micro-vibration is not sufficient enough for ink droplets to be ejected from the nozzle 12. The ink includes a dispersion medium and solid particles of which specific gravity is larger than that of the dispersion medium. The droplet ejection device also includes refreshing means. When the head 1 is positioned in a non-printing region, the refreshing means performs micro-vibration operation to apply a plurality of micro-vibration pulses and, after the micro-vibration operation, performs discard operation to apply a plurality of ejection pulses to eject the amount of ink droplets equal to or greater than the capacity of the ink chamber from the nozzle 12.

Description

  The present invention relates to a droplet ejection device and a nozzle recovery method of the droplet ejection device, and more particularly, droplet ejection that can suppress the sedimentation of solid particles contained in ink and perform stable droplet ejection for a long time. The present invention relates to a nozzle recovery method for an apparatus and a droplet ejection apparatus.

  A droplet ejection apparatus that performs printing by ejecting droplets from a head is generally used as an ink jet printer for various industrial applications. The application of this industrial inkjet has been increasing year by year, and in recent years, it has been used not only for printing on paper, fabrics, plastic sheets, etc., but also for printing patterns on the surface of ceramic tiles. Accordingly, the droplet ejecting apparatus is required to have a performance capable of stably ejecting a wide variety of inks for a long time.

  However, when printing is performed by ejecting liquid droplets from the head using ceramic ink containing ceramic solid particles or white ink containing solid particles such as titanium oxide as the ink, there is no print data In addition, while the head is present in the non-printing area where printing is not performed, the solid particles in the ink settle in the ink chamber. This is because these solid particles have a higher specific gravity than the dispersion medium in the ink. If sedimentation of solid particles occurs in the ink chamber, the density of solid particles in the vicinity of the nozzle may increase and nozzle clogging may occur. In addition, when solid particles having a high density are cured, it becomes impossible to inject permanently.

  Even when the nozzle is placed sideways, the concentration distribution in the ink in the ink chamber is caused by the sedimentation of the solid particles, so even if the droplets can be ejected, the solid particles in the droplets do not reach the proper concentration and are ejected. There is a risk of disturbing speed and non-uniform image.

  Conventionally, a technique has been proposed in which ink is circulated using a pressure difference between a head and an ink tank in order to reduce sedimentation of solids such as pigments in the ink (Patent Document 1). However, the ink on the head side circulated by this is the ink in the common ink chamber that supplies ink in common to each ink chamber of the head, and the supplied ink cannot be circulated in each ink chamber. For this reason, it is not possible to suppress sedimentation of solid particles generated in the ink chamber when printing is suspended.

  As a countermeasure against nozzle clogging when printing is stopped, a technique is known in which a preliminary waveform is applied to each ink chamber to vibrate the meniscus and flow ink in the ink chamber immediately before resuming ejection (Patent Document 2). . However, this technique eliminates nozzle clogging due to an increase in viscosity due to evaporation of volatile components in the ink. Since the ink flow caused by such meniscus vibration is extremely small, it is effective in eliminating nozzle clogging due to an increase in viscosity, but by simply vibrating the meniscus, the solid particles settled to some extent in the ink chamber. The situation could not be resolved sufficiently.

  It is also known to detect the viscosity of ink and adjust the intensity of fine vibration and the amount of liquid droplets when ink is ejected according to the viscosity (Patent Document 3). However, this prevents nozzle clogging caused by the evaporation of the liquid and the thickening of the ink, and does not solve the problem caused by the sedimentation of solid particles contained in the ink.

Special table 2011-506152 gazette JP 2000-203020 A JP 2012-96423 A

  Therefore, an object of the present invention is to provide a droplet ejection device that can effectively eliminate sedimentation of solid particles contained in ink and can eject droplets stably for a long time.

  Another object of the present invention is to provide a nozzle recovery method for a droplet ejection apparatus that can effectively eliminate sedimentation of solid particles contained in ink and can stably eject droplets for a long time. To do.

  Other problems of the present invention will become apparent from the following description.

1. An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a droplet ejection device having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
When the head is present in a non-printing area where the printing is not performed, a micro-vibration operation for applying the plurality of micro-vibration pulses to the energy application unit, and a plurality of the energy application unit after the micro-vibration operation are performed. A droplet ejecting apparatus comprising: a refresh unit that applies the ejection pulse and performs a discharge operation for ejecting a droplet amount equal to or larger than a volume of the ink chamber from the nozzle.

2. A droplet velocity detecting means for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
2. The droplet ejection apparatus according to claim 1, wherein the refresh unit is executed after it is detected that a detection result of the droplet velocity detection unit is below a preset threshold value.

3. A pause period detecting means for detecting a period during which ejection of liquid droplets from the nozzle is paused when the head is present in a print area where the print is performed;
2. The droplet ejection apparatus according to claim 1, wherein the refresh unit is executed after it is detected that a detection result of the pause period detection unit exceeds a preset threshold value.

4). An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a droplet ejection device having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
Fine vibration means for performing only a fine vibration operation for applying a plurality of the fine vibration pulses to the energy applying means;
A micro-vibration operation in which a plurality of micro-vibration pulses are applied to the energy application unit, and a plurality of ejection pulses are applied to the energy application unit after the micro-vibration operation, and the volume of the ink chamber is equal to the nozzle. A refresh means for performing a discharging operation for ejecting the above-mentioned droplet amount;
A droplet ejecting apparatus comprising: a selection unit that selects and executes either the fine vibration unit or the refresh unit when the head is in a non-printing area where the printing is not performed.

5. A droplet velocity detecting means for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
After the detection means detects that the detection result of the droplet velocity detection means falls below a preset threshold, either the fine vibration means or the refresh means is selected according to the detection result. 5. The droplet ejecting apparatus according to 4 above, which is selected and executed.

6). A pause period detecting means for detecting a period during which ejection of liquid droplets from the nozzle is paused when the head is present in a print area where the print is performed;
The selection means detects either the fine vibration means or the refresh means according to the detection result after it is detected that the detection result of the droplet velocity detection means exceeds a preset threshold value. 5. The droplet ejecting apparatus according to 4 above, which is selected and executed.

  7). 7. The liquid droplet ejection according to any one of 1 to 6, wherein in the fine vibration operation, the applied frequency is increased as the specific gravity increases according to the specific gravity of the solid particles with respect to the dispersion medium. apparatus.

8). An ink tank for storing the ink to be supplied to the head;
A circulation means for circulating the ink between the head and the ink tank;
8. The droplet ejecting apparatus according to any one of 1 to 7, wherein the circulation unit circulates the ink at least during a period in which the refresh unit is executed.

9. When the head is present in a non-printing area where the printing is not performed, at least one of a wiping operation for scraping off dirt on the nozzle surface opened by the nozzle with a blade or a wiping operation for wiping ink on the nozzle surface Having nozzle maintenance means for performing
9. The droplet ejection apparatus according to any one of 1 to 8, wherein neither the fine vibration unit nor the refresh unit is executed during a period in which the nozzle maintenance unit is being executed.

  10. 10. The droplet ejection apparatus according to any one of 1 to 9, wherein the ink has a specific gravity difference of 0.2 or more between the dispersion medium and the solid particles.

  11. 11. The droplet ejecting apparatus according to any one of 1 to 10, wherein the ink does not volatilize from the nozzles by drying.

12 An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a method for recovering a nozzle of a droplet ejection apparatus having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
When the head is present in a non-printing area where the printing is not performed, a micro-vibration operation for applying the plurality of micro-vibration pulses to the energy application unit, and a plurality of the energy application unit after the micro-vibration operation are performed. A method for recovering a nozzle of a droplet ejection apparatus, comprising: a refresh step of applying the ejection pulse and performing a discharge operation for ejecting a droplet amount equal to or greater than the volume of the ink chamber from the nozzle.

13. A droplet velocity detecting step for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
13. The method for recovering a nozzle of a droplet ejection apparatus according to claim 12, wherein the refreshing step is executed after it is detected that the detection result of the droplet velocity detection step is below a preset threshold value.

14 A pause period detecting step of detecting a period in which the ejection of droplets from the nozzle is paused when the head is present in the print area where the print is performed;
13. The method for recovering a nozzle of a droplet ejection apparatus according to claim 12, wherein the refreshing step is executed after it is detected that the detection result of the pause period detection step exceeds a preset threshold value.

15. An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a method for recovering a nozzle of a droplet ejection apparatus having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
A micro-vibration step of performing only a micro-vibration operation of applying a plurality of micro-vibration pulses to the energy applying means;
A micro-vibration operation in which a plurality of micro-vibration pulses are applied to the energy application unit, and a plurality of ejection pulses are applied to the energy application unit after the micro-vibration operation, and the volume of the ink chamber is equal to the nozzle. A refreshing step for performing a discharge operation for ejecting the above droplet amount,
A nozzle recovery method for a droplet ejection apparatus, wherein when the head exists in a non-printing area where the printing is not performed, either the fine vibration process or the refreshing process is selected and executed.

16. A droplet velocity detecting step for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
After detecting that the detection result of the droplet velocity detection step is below a preset threshold value, either the fine vibration step or the refresh step is selected and executed according to the detection result. 16. The method for recovering a nozzle of a droplet ejection device as described in 15 above.

17. A pause period detecting step of detecting a period in which the ejection of droplets from the nozzle is paused when the head is present in the print area where the print is performed;
After detecting that the detection result of the pause period detection step exceeds a preset threshold value, either the fine vibration step or the refresh step is selected and executed according to the detection result 16. The method for recovering a nozzle of a droplet ejection device as described in 15 above.

  18. 18. The liquid droplet ejection according to any one of 12 to 17, wherein in the fine vibration operation, the applied frequency is increased as the specific gravity increases in accordance with the specific gravity of the solid particles with respect to the dispersion medium. Device nozzle recovery method.

19. An ink tank for storing the ink to be supplied to the head;
19. The nozzle recovery method for a droplet ejection apparatus according to any one of 12 to 18, wherein the ink is circulated between the head and the ink tank at least during a period in which the refresh process is performed.

20. When the head exists in a non-printing area where the printing is not performed, at least one of a wiping step of scraping off dirt on the nozzle surface opened by the nozzle with a blade or a wiping step of wiping off ink on the nozzle surface Has a nozzle maintenance process to perform that process,
20. The nozzle recovery method for a droplet ejection apparatus according to any one of 12 to 19, wherein neither the fine vibration process nor the refresh process is executed during a period in which the nozzle maintenance process is executed.

  21. 21. The nozzle recovery method for a droplet ejection apparatus according to any one of 12 to 20, wherein the ink has a specific gravity difference of 0.2 or more between the dispersion medium and the solid particles.

  22. The method for recovering a nozzle of a droplet ejection apparatus according to any one of 12 to 21, wherein the ink does not volatilize from the nozzle by drying.

  According to the present invention, it is possible to provide a droplet ejection device that can effectively eliminate sedimentation of solid particles contained in ink and can stably eject droplets for a long time.

  In addition, according to the present invention, it is possible to provide a nozzle recovery method for a droplet ejection device that can effectively eliminate sedimentation of solid particles contained in the ink and can stably eject droplets for a long time. it can.

A perspective view showing an example of a line-type droplet ejection device Cross-sectional view of the head in the droplet ejection device Block diagram showing schematic configuration of droplet ejection device (A) is an injection pulse, (b) is a diagram showing an example of a micro-vibration pulse. Diagram explaining the volume of the ink chamber The figure which shows an example of the application pattern of the fine vibration pulse and injection pulse at the time of refresh The figure explaining an example of the detection means which detects the sedimentation state of solid particles The figure which shows an example of the flow which detects the velocity of a droplet with a droplet velocity detection apparatus prior to refreshing The figure which shows an example of the flow which detects the ejection stoppage period of a droplet prior to refreshing (A) (b) is a figure which shows the example of the application pattern of the fine vibration pulse in each performing only a fine vibration operation | movement. The figure which shows an example of the flow which selects fine vibration operation and refresh by using the detection result of a droplet velocity detection device as a trigger The figure which shows an example of the flow which selects fine vibration operation | movement and a refresh using the detection result of the ejection stop period of a droplet as a trigger The figure which shows an example of the table which prescribed | regulated the relationship between the ratio of the specific gravity difference of a solid particle with respect to the specific gravity of a dispersion medium, and the applied frequency of a fine vibration pulse. The figure explaining an example of the structure for circulating ink External view showing an example of a scan type droplet ejection device

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a perspective view illustrating an example of a droplet ejection device, and FIG. 2 is a cross-sectional view illustrating an example of a head. In the figure, 100 is a droplet ejection device, 1 is a head, and 2 is a conveyor belt.

  In the droplet ejection device 100, ceramic tiles C as recording materials are placed at intervals above the conveyance surface 2a of the conveyance belt 2 that is rotationally driven in one direction, and conveyed in the direction of the arrow in the figure. It is like that. In the head 1, a plurality of nozzles 12 are arranged along the X direction in the drawing along the width direction of the transport belt 2, and the nozzle surface is disposed so as to face vertically downward facing the transport surface 2 a. Then, the printing area on the surface of the ceramic tile C conveyed at a constant speed by the conveying belt 2 includes, for example, ceramic particles having a specific gravity larger than that of the dispersion medium as solid particles from each nozzle 12 based on the printing data. A predetermined image is formed by ejecting ceramic ink.

  As shown in FIG. 2, the head 1 has a plurality of ink chambers 11 arranged in the X direction. In this example, 20 ink chambers 11 are arranged in one row in the X direction, but the number of ink chambers 11 and the number of columns are not particularly limited. In the head 1, all the ink chambers 11 are provided corresponding to the ink chambers 11 by supplying ink in the common ink chamber 13 provided so as to communicate with the ink chambers 11. This is an ink chamber in which droplets can be ejected from the nozzle 12.

  In the head 1, a partition wall 14 that separates adjacent ink chambers 11 and 11 is formed by a piezoelectric element. Drive electrodes (not shown) are formed on the surfaces of the partition walls 14 facing the ink chamber 11. In the head 1, when a drive pulse having a predetermined voltage is applied to each drive electrode from a head driver described later, the partition wall 14 is deformed and the volume in the ink chamber 11 is changed. When this volume change becomes so great that the ink in the ink chamber 11 is ejected from the nozzle 12 formed on the nozzle plate 15, ejection energy is applied to the ink in the ink chamber 11, and droplets are ejected from the nozzle 12. It has become so. In the head 1, an energy applying unit that applies energy to the ink in the ink chamber 11 is configured by the partition wall 14 on which the drive electrode is formed.

  Here, the ink used in the present invention contains solid particles having a specific gravity larger than that of the dispersion medium in addition to the dispersion medium. The dispersion medium is not particularly limited. Examples of the solid particles include pigment particles such as titanium oxide in addition to the ceramic particles in the ceramic ink described above.

  The larger the specific gravity difference with respect to the dispersion medium, the faster the settling speed of the solid particles, and the more easily settles in the ink chamber, and the problem of the present invention becomes remarkable. The specific gravity difference between the dispersion medium and the solid particles in the present invention is preferably 0.2 or more, since the effects of the present invention are remarkably obtained.

  In the present invention, ink that does not volatilize by drying at room temperature and normal pressure is used. Here, “not volatilized” means an ink having a content of a substance having a vapor pressure greater than that of water at room temperature of 10% or less, preferably 5% or less. Such an ink does not cause a problem of an increase in viscosity due to evaporation of a volatile component, which is observed when a volatile ink such as a water-based ink is used. Examples of such ink include UV ink and oil ink.

  FIG. 3 is a block diagram illustrating a schematic configuration of the inside of the droplet ejection device 100.

  101 is a CPU that performs overall control of the droplet ejection apparatus 100, 102 is a print data memory that stores print data formed in a print area on the surface of the ceramic tile C, 103 is an encoder that detects the amount of movement of the transport belt 2, and 104 Is a belt conveyance motor that rotationally drives the conveyance belt 2, 105 is a head driver that applies a pulse for deforming the partition wall 14 to the drive electrode of the head 1, and 106 is a drive signal provided to the head driver 105 and applied to the head 1. A drive pulse generation unit 107 for generating a drive pulse as described above, 107 is provided in the CPU 101, and a fine vibration control unit for controlling a fine vibration operation for giving a fine vibration to the ink in the ink chamber 11, and 108 is provided in the CPU 101. 11 is a discharge control unit that controls a discharge operation for discharging the ink in the ink.

  The fine vibration control unit 107 causes the ink in the ink chamber 11 to slightly vibrate and disperse the solid particles by imparting kinetic energy when the head 1 exists in a non-printing area where printing based on the printing data is not performed. The drive of the head 1 is controlled via the head driver 105 so as to perform a fine vibration operation that facilitates. In the present invention, the fine vibration control unit 107 constitutes fine vibration means.

  The discharge control unit 108 forcibly discharges ink in the ink chamber 11 when the head 1 exists in a non-printing area where printing based on the print data is not performed, and the ink in the ink chamber 11 is replaced with new ink. The drive of the head 1 is controlled via the head driver 105 so as to perform a discharge operation to replace the head 1. In the present invention, the fine vibration control unit 107 and the discharge control unit 108 constitute a refresh means.

  As shown in FIG. 4A, the pulse generated by the drive pulse generator 106 includes an ejection pulse P1 for ejecting a droplet from the nozzle 12, and a nozzle as shown in FIG. 4B. 12 includes a micro-vibration pulse P2 that gives micro-vibration to the ink in the ink chamber 11 to the extent that droplets are not ejected from the nozzle 12. The drive pulse generator 106 selects one of these drive pulses according to an instruction from the CPU 101 and applies it to the drive electrodes formed on the partition 104 of the head 1.

  When ink containing solid particles having a specific gravity larger than that of the dispersion medium is ejected from the nozzle 12 according to the printing data, the period when the ejection from the nozzle 12 is stopped when the head 1 is in the printing region, Even after a short period of time during which injection is suspended when in the non-printing region, there is a risk that defective injection such as nozzle clogging may occur due to sedimentation of solid particles. Therefore, in the present invention, when the head 1 is present in this non-printing area, refreshing is performed by ejecting droplets from each nozzle 12 and discharging ink based on the control of the CPU 101 to stabilize ejection. Yes.

  In the present invention, the non-printing area is an area off the recording material, unlike a printing area in which a droplet is ejected from the nozzle 12 based on the printing data and printing is performed on the recording material. This is an area where there is no print data and no print based on the print data is performed. When viewed from the head 1, the print area and the non-print area usually come alternately. In this droplet ejection device 100, a space between the ceramic tiles C and C continuously placed on the transport surface 2a with a space is a non-printing area where printing based on printing data is not performed. That the head 1 has come to this non-printing area is detected by the amount of movement of the conveyor belt 2 detected by the encoder 103.

  The refresh of the head 1 executed by the CPU 101 is performed by a fine vibration operation under the control of the fine vibration control unit 107 and a discharge operation under the control of the discharge control unit 108 performed following this fine vibration operation. That is, when the head 1 exists in the non-printing area until one ceramic tile C passes directly under the head 1 and the next ceramic tile C reaches directly under the head 1, the fine vibration control unit A micro-vibration operation that applies a plurality of micro-vibration pulses P2 to the drive electrodes of the partition wall 14 under the control of 107 and applies micro-vibration to the ink in the ink chamber 11 to the extent that droplets are not ejected from the nozzles 12, and Then, a plurality of ejection pulses P1 are applied to the drive electrode of the partition wall 14 under the control of the discharge controller 108, so that the droplet volume becomes equal to or larger than the volume of the ink chamber 11 from the nozzle 12. And a discharge operation for injecting.

  The volume of the ink chamber 11 refers to the volume of the ink flow path between the boundary with the common ink chamber 13 and the tip opening of the nozzle 12. Therefore, this volume does not include the volume inside the common ink chamber 13. In the head 1 shown in the present embodiment, as shown in FIG. 5, a nozzle is formed from an opening 11 a of the ink chamber 11 that is a boundary with the common ink chamber 13 between both partition walls 14 and 14 that define the ink chamber 11. This is the volume of the space of the distance D that becomes the ink flow path to the tip opening 12a of the nozzle 12 that opens on the surface (nozzle surface) of the plate 15.

  Since the volume of one droplet ejected by one ejection pulse P1 is known in advance, the amount of droplets that is equal to or larger than the volume of the ink chamber 11 depends on the total number of ejection pulses P1 applied (total application time). Can be prescribed.

  By performing refresh while the head 1 is present in the non-printing area, the entire amount of ink stored in the ink chamber 11 is forcibly discharged from the nozzle 12. For this reason, even if solid particles settle in the ink chamber 11, all of the ink in the ink chamber 11 is replaced with ink newly supplied from the common ink chamber 13, and the solid particles in the ink chamber 11 are replaced. No longer remains settling. As a result, the concentration of solid particles in the ink in the ink chamber 11 can be kept constant, the occurrence of nozzle clogging is suppressed, and stable ejection over a long period of time is possible.

  In addition, refreshing is not limited to simply discharging droplets, but before the droplets are discharged, fine vibration is applied to the ink in the ink chamber 11 and kinetic energy is given to the solid particles. The settled or agglomerated solid particles are easily dispersed, and can be smoothly discharged from the nozzle 12 by the energy applied at the time of subsequent discharge. For this reason, the settled solid particles do not remain in the ink chamber 11, and the entire amount of ink in the ink chamber 11 can be replaced efficiently. Even if the droplets are merely discharged without giving such a slight vibration to the ink in a state where the solid particles are settling, the solid particles settled in the ink chamber 11 can be smoothly discharged from the nozzle 12. Otherwise, the solid particles may remain or the clogged solid particles may cause nozzle clogging.

  FIG. 6 shows an example of an application pattern of the emission pulse P1 and the fine vibration pulse P2 when performing refresh. Here, when the head 1 enters the non-printing region, first, the micro-vibration pulse application operation for continuously applying the plurality of micro-pulses P2 is continued for a predetermined time t1, and then the plurality of ejection pulses P1 are continuously performed. The injection pulse application operation to be applied is continued for a predetermined time t2. Then, the fine vibration pulse application operation at time t1 and the injection pulse application operation at time t2 are repeated alternately three times.

  In order to make the amount of droplets discharged from the nozzles 12 within one non-printing region equal to or larger than the volume of the ink chamber 11, as shown in FIG. In the case where the ejection pulse application operation at a single interval of time t2 is performed in a plurality of times, the total droplet amount ejected by the multiple ejection pulse application operations is equal to or greater than the volume of the ink chamber 11. Droplets can be ejected to a quantity. According to this, the ink containing the solid particles settled in the ink chamber 11 is discharged little by little while being dispersed little by little by applying the fine vibration. Even when it is difficult to discharge, the entire amount of ink in the ink chamber 11 can be replaced effectively.

  In addition, it is possible to eject droplets so that the volume of the droplets is equal to or larger than the volume of the ink chamber 11 for each section of ejection pulse application operation in one non-printing area. In this case, the entire amount of ink is replaced a plurality of times within one non-printing area. According to this, since the amount of ink flowing around the ink chamber 11 including the common ink chamber 13 in the head 1 is increased accordingly, the ink in a state where the solid particles are uniformly dispersed can be supplied into the ink chamber 11. Becomes higher.

  The number of occurrences of the fine vibration pulse application operation at time t1 and the injection pulse application operation at time t2 in one non-printing region is not particularly limited as long as the fine vibration pulse application operation is performed immediately before the injection pulse application operation. Absent. In FIG. 6, the time t1 of the fine vibration pulse P2 is made uniform all three times, and the time t2 of each ejection pulse P1 is made uniform three times. However, these times t1 and t2 are not uniform in each application operation. You may set so that. That is, the number of ejection pulses P1 or micro-vibration pulses P2 within each application operation may be varied for each application operation.

  The refresh that performs the fine vibration operation and the discharge operation can be performed every time the head 1 reaches the non-printing area. For example, a large amount of liquid droplets are continuously ejected from the nozzle 12 in the printing area. In some cases, depending on the type of ink, the sedimentation of the solid particles in the ink in the ink chamber 11 may not progress as much as when the difference in specific gravity between the dispersion medium and the solid particles is relatively small. In such a case, if the ink discharge operation is performed every time the head 1 reaches the non-printing area, the ink is consumed wastefully. In addition, since droplets containing solid particles are likely to generate satellites, there is a concern that the satellites generated at the time of injection are scattered as mists, leading to contamination of the surroundings. In order to suppress such waste of ink and surrounding contamination by satellites, it is desirable to minimize the number of droplets that are discharged by the discharging operation.

  For this reason, the CPU 101 selects whether to perform refresh according to the sedimentation state of the solid particles in the ink in the ink chamber 11 when the head 1 is present in the non-printing area, that is, the progress of sedimentation. It is also preferable. Thereby, it is possible to prevent a wasteful discharge operation from being performed, and it is possible to suppress wasteful consumption of ink and surrounding contamination due to satellites.

  In general, the ejection speed of droplets ejected from the nozzle 12 becomes slower as the amount of solid particles contained in the droplets increases. For this reason, it is possible to estimate the progress of sedimentation of solid particles in the ink in the vicinity of the nozzle 12 in the ink chamber 11 from the ejection speed of the droplet.

  FIG. 7 shows a droplet velocity detection device 3 that is an example of a detection unit that detects the droplet ejection velocity. As shown in FIG. 3, the droplet velocity detection device 3 operates in response to an instruction from the CPU 101 and transmits the result to the CPU 101.

  The droplet velocity detection device 3 includes a light projecting unit 31 that includes an LED or a laser that emits the detection light L, and a light receiving unit 32 that includes a photosensor that receives the detection light L. The optical axis is arranged in the vicinity of the nozzle 12 so as to be along the X direction that is the arrangement direction of the nozzles 12 and parallel to the nozzle surface. Thereby, the droplet a ejected from each nozzle 12 intersects with the detection light L, and a shadow when the droplet a passes is captured by the light receiving unit 32. When the ejection pulse P1 is applied to one of the ink chambers 11 and the droplet a is ejected from the nozzle 12, the droplet velocity detecting device 3 causes the light receiving unit 32 to detect the droplet a from the application of the ejection pulse P1. The ejection speed of the droplet a is obtained from the time taken to capture the shadow of and the distance from the nozzle 12 to the optical axis of the detection light L.

  In either the CPU 101 or the droplet velocity detection device 3, a threshold value indicating a lower limit of a preferable ejection velocity of the droplet a is set in advance. When the ejection speed of the droplet a detected when the head 1 is present in the non-printing area falls below this threshold, the sedimentation of the solid particles in the ink in the ink chamber 11 proceeds, and refreshing is performed. It can be determined that the state is to be performed.

  FIG. 8 shows an example of a flow for detecting the velocity of the droplet a by the droplet velocity detection device 3 prior to refreshing when the head 1 comes to the non-printing area. When the head 1 reaches the non-printing area, the droplet velocity detection device 3 first ejects the droplet a from each nozzle 12 of the head 1 to detect the ejection velocity of the droplet a (S1). The detection result is transmitted to the CPU 101, and from the result, the CPU 101 determines whether or not the ejection speed of the droplet a is below the threshold value and solid particles are settling (S2). If this is the case, a refresh operation consisting of a fine vibration operation and a discharge operation is started thereafter (S3). On the other hand, if the ejection speed of the droplet a has not yet fallen below the threshold, it is determined that the solid particles in the ink chamber 11 have not settled so far as to be discharged, and refreshing in the non-printing area is performed. Do not execute. For this reason, wasteful consumption of ink and surrounding contamination by satellite can be suppressed.

  The refresh after the droplet velocity is detected is performed in all the ink chambers 11 of the head 1 when it is determined that the ejection velocity of the droplet a ejected from any nozzle 12 of the head 1 is lower than the threshold value. Alternatively, it may be performed separately, or may be performed individually only on the ink chamber 11 from which the droplet a having an ejection speed lower than the threshold is ejected. In the latter case, wasteful consumption of ink and surrounding contamination by satellites can be further suppressed.

  In addition, when a plurality of heads 1 are provided for each ink color, an appropriate nozzle recovery operation is performed for each head 1 by detecting the ejection speed of droplets for each head 1 and determining whether or not to perform refresh. Can be executed.

  The sedimentation of the solid particles in the ink in the ink chamber 11 proceeds when a period without print data continues for a long time even in the print area. When a plurality of heads 1 are provided for each color, for example, a head that ejects white ink that is often used as a base may not be used for a long time. For this reason, the progress of sedimentation of solid particles in the ink in the vicinity of the nozzles 12 in the ink chamber 11 can be estimated from the suspension period of the droplet ejection in the ink chamber 11 in the printing region. Therefore, it is also preferable that the CPU 101 selects whether or not to perform the discharge operation according to the suspension period of the droplet ejection from the nozzle 12 when the head 1 is present in the printing area where printing is performed. This also makes it possible to avoid unnecessary refreshing, and it is possible to suppress wasteful consumption of ink and surrounding contamination due to satellites.

  FIG. 9 shows an example of a flow for selecting whether or not to perform refresh according to the droplet ejection suspension period. When the head 1 reaches the non-printing area, first, the ejection stop period of the droplets of each nozzle 12 in the printing area is detected (S10). The ejection suspension period of droplets from the nozzles 12 can be obtained by analyzing the print data stored in the print data memory 102 in the CPU 101, for example. The detection result is transmitted to the CPU 101.

  In the CPU 101, a threshold value indicating the upper limit of the injection suspension period is set in advance. From the detection result, the CPU 101 determines whether or not the solid particle sedimentation has progressed to the extent that the injection suspension period has exceeded the threshold value for a long period of time (S11). Then, if it is determined that the value has exceeded, refreshing by the fine vibration operation and the discharge operation is started thereafter (S12). On the other hand, when the ejection suspension period is below the threshold value, it is determined that the solid particle sedimentation in the ink chamber 11 has not progressed so much as to be refreshed, and the refresh in the non-printing area is not executed. For this reason, wasteful consumption of ink and surrounding contamination by satellite can be suppressed.

  The refresh after the ejection pause period is detected is performed for all the ink chambers 11 of the head 1 when it is determined that the ejection pause period of any nozzle 12 of the head 1 exceeds the threshold value. Alternatively, it may be performed individually only for the ink chamber 11 in which the ejection suspension period exceeds the threshold value. In the latter case, wasteful consumption of ink and surrounding contamination by satellites can be further suppressed.

  Further, when a plurality of heads 1 are provided for each ink color, an appropriate nozzle recovery operation is executed for each head 1 by detecting an ejection pause period for each head 1 and determining whether or not to perform refresh. be able to.

  In the embodiment described above, when the head 1 exists in the non-printing area, the CPU 101 controls the fine vibration control unit 107 and the discharge control unit 108 to perform refresh. However, since refreshing involves ejection of droplets, ink consumption increases. For this reason, the droplet ejecting apparatus 100 applies a plurality of micro-vibration pulses P2 to the drive electrode of the partition wall 14 of the ink chamber 11 when performing refreshing composed of the micro-vibration operation and the discharge operation, and thereby the liquid ejection device 100 It is also preferable to select and execute either the case of performing only the fine vibration operation without performing the droplet ejection operation.

  Of these, the refresh has already been described, and therefore the description thereof is omitted here. On the other hand, when only the fine vibration operation is selected and executed, the pulse applied from the head driver 105 to the drive electrode formed on the partition wall 14 of the head 1 is a pulse among the pulses generated by the drive pulse generator 106. Only the fine vibration pulse P2 illustrated in 4 (b) is used.

  FIG. 10 shows an example of the application pattern of the fine vibration pulse P2 when only the fine vibration operation is performed. The application pattern shown in (a) is such that a fine vibration pulse application operation for continuously applying a plurality of fine vibration pulses P2 is continued while the head 1 exists in the non-printing area. . On the other hand, in the application pattern shown in (b), the minute vibration pulse application operation is continued for a predetermined time, and this minute vibration pulse application operation for a predetermined time is repeated a plurality of times at intervals. The duration of the one-minute micro-vibration pulse application operation is not limited to be set uniformly in one non-printing region, and may be set to be non-uniform.

  When the head 1 is present in the non-printing area, the operator can manually set in advance, for example, by a changeover switch or the like to select whether to perform only the fine vibration operation or to perform refreshing consisting of the fine vibration operation and the discharge operation. However, it is preferable that the CPU 101 automatically selects and executes it by using the progress of the settling of solid particles in the ink chamber 11 when the head 1 comes to the non-printing area as a trigger. The progress of the sedimentation of the solid particles in the ink in the ink chamber 11 is detected by setting a predetermined threshold and detecting the ejection speed of the liquid droplet using the liquid droplet velocity detection device 3 shown in FIG. be able to.

  FIG. 11 shows an example of a flow triggered by the detection result of the droplet velocity detection device 3 when selecting whether to perform only the fine vibration operation or to perform the refresh. When the head 1 reaches the non-printing area, the droplet velocity detection device 3 first ejects the droplet a from the nozzle 12 of the head 1 to detect the ejection velocity (S20). The detection result is transmitted to the CPU 101.

  In the CPU 101, two threshold values of the injection speed corresponding to the progress of solid particle settling are set in advance. The first threshold value is a threshold value for discriminating whether to perform a fine vibration operation or to do nothing. The second threshold value is set to a value lower than the first threshold value, indicates a state in which solid particles have settled to some extent, and is a threshold value for determining whether to perform only a fine vibration operation or to perform refreshing. .

  The CPU 101 first compares the detection result of the droplet velocity detection device 3 with the first threshold value, and determines whether or not the solid particles have settled to the extent that the fine vibration operation is performed below the first threshold value. (S21). As a result, if it has not yet fallen below the first threshold value, it is determined that the solid particle settling in the ink chamber 11 has not progressed to the extent that the nozzle recovery operation is performed, and no nozzles are present in the non-printing area. No recovery action is performed. For this reason, wasteful consumption of ink and surrounding contamination by satellite can be suppressed.

  On the other hand, when it is determined that the value is below the first threshold, the detection result is compared with the second threshold (S22). As a result, when it is determined that the second threshold value is also below, refreshing including a fine vibration operation and a discharge operation is started thereafter (S23). If it is determined that it is not lower than the second threshold value, it is determined that the solid particles have settled to some extent but need not be refreshed, and thereafter only the fine vibration operation is performed (S24).

  Thereby, it is possible to take an appropriate response according to the state of the ink in the ink chamber 11. When it is selected to perform only the micro-vibration operation, droplets are not ejected, so that wasteful consumption of ink and surrounding contamination by satellites can be suppressed.

  Further, instead of the detection result of the droplet velocity detection device 3, as shown in the flow of FIG. 12, the detection result of the droplet ejection suspension period can be used as a trigger. That is, when the head 1 reaches the non-printing area, first, the droplet ejection suspension period of each nozzle 12 in the printing area is detected based on the printing data (S30). The detection result is transmitted to the CPU 101.

  Then, the CPU 101 first compares the detection result of the injection suspension period with the first threshold value, and determines whether or not the solid particles have settled to the extent that the fine vibration operation is performed exceeding the first threshold value ( S31). As a result, if it is below the first threshold value, it is determined that the solid particles in the ink chamber 11 have not settled so far as to perform the nozzle recovery operation, and no nozzle recovery is performed in the non-printing area. Does not perform any actions. For this reason, wasteful consumption of ink and surrounding contamination by satellite can be suppressed.

  On the other hand, when it is determined that the first threshold value is exceeded, the detection result is compared with a second threshold value set to a value higher than the first threshold value (S32). As a result, if it is determined that the second threshold value is also exceeded, then refresh including the fine vibration operation and the discharge operation is started (S33). If it is determined that the second threshold has not yet been exceeded, it is determined that the solid particles have settled to some extent but need not be refreshed, and thereafter only the fine vibration operation is performed (S34). Also by this, the same effect as the case of detecting the ejection speed of the droplet can be obtained.

  Also in these cases, when a plurality of heads 1 are provided for each ink color, the droplet ejection speed and ejection pause period are detected for each head 1 to determine whether only the fine vibration operation is performed or refresh is performed. Thus, an appropriate nozzle recovery operation can be executed for each head 1.

  Further, in each of the flows shown in FIGS. 11 and 12, the fine vibration operation may be performed whenever the head 1 comes to the non-printing area. In this case, only one set value of the threshold value is required, and it may be determined whether to perform only the fine vibration operation or to perform refresh including the fine vibration operation and the discharge operation by comparison with this threshold value.

  In addition, whether to perform only the fine vibration operation or to perform refresh may be selected and executed according to a preset sequence. For example, the selection trigger is set according to the number of times the head 1 reaches the non-printing area, and when the head 1 exists in the non-printing area, a slight vibration operation is always performed, and the head 1 reaches the non-printing area for the third time. It is possible to perform refreshing consisting of a fine vibration operation and a discharge operation each time. Also, the trigger for selection is set according to the time, normally only the fine vibration operation is performed, and refreshing consisting of the fine vibration operation and the discharge operation is performed every time a predetermined time has elapsed since the start of printing or the previous refresh execution. can do.

  By the way, the sedimentation rate of the solid particles increases as the specific gravity of the solid particles with respect to the dispersion medium increases, and the sedimentation rate becomes easier. For example, even with the same head, the specific gravity of the solid particles with respect to the dispersion medium may differ depending on the type of ink used. Further, in the case of using a plurality of heads 1, the solid particles with respect to the dispersion medium between the heads of different colors can be obtained by changing the type of solid particles contained in the ink depending on the type (color) of ink for each head 1. Differences in the specific gravity of the particles may occur. In such a case, if uniform micro-vibration operation is performed regardless of the specific gravity of the solid particles relative to the dispersion medium, it may be difficult to sufficiently disperse the solid particles depending on the size of the specific gravity. The

  For this reason, when giving a slight vibration to the ink in the ink chamber 11 by the fine vibration pulse P2, it is preferable to increase the applied frequency as the specific gravity increases according to the specific gravity of the solid particles with respect to the dispersion medium. The greater the specific gravity, the higher the applied frequency of the micro-vibration pulse P2, so that the ink in the ink chamber 11 can be efficiently micro-vibrated, and the dispersion of solid particles can be effectively promoted.

  The magnitude of the specific gravity of the solid particles with respect to the dispersion medium is determined, for example, by providing an input switch (not shown) in the droplet ejection device 100 and setting an ink tank or an ink cartridge for storing ink in the device. Depending on the type, it may be performed manually by an operator's input operation, or when the ink tank or ink cartridge is set in the apparatus, the type of ink provided in the ink tank or ink cartridge is determined. The identification information may be automatically performed by recognizing it by a recognition unit (not shown) provided in the droplet ejection device 100. These input results and identification results are transmitted to the CPU 101, and the fine vibration control unit 107 controls the fine vibration operation based on the input results and identification results.

  FIG. 13 shows an example of a table that is preferably used when the applied frequency is adjusted according to the specific gravity of the solid particles with respect to the dispersion medium. In this table, the relationship between the magnitude of the specific gravity of the solid particles with respect to the dispersion medium (ratio of the specific gravity difference of the solid particles with respect to the specific gravity of the dispersion medium) and the application frequency of the fine vibration pulse is defined. The When the specific gravity of the solid particles with respect to the input or identified dispersion medium is relatively small, the settling speed of the solid particles is relatively slow, so the applied frequency is decreased, and the applied frequency is increased as the specific gravity is increased. Increase As a result, it is possible to execute a fine fine vibration operation according to the difference in the sedimentation speed of the solid particles, and to achieve more efficient nozzle recovery.

  As shown in FIG. 14, the ink in the common ink chamber 13 of the head 1 can be circulated with the ink tank 4 that stores the ink. A supply pipe 41 and a return pipe 42 are connected between the common ink chamber 13 of the head 1 and the ink tank 4, and a circulation pump 43 is provided in the return pipe 42, and these supply pipe 41, return pipe 42 and The circulation pump 43 constitutes a circulation means. The circulation pump 43 is driven so that the ink circulates between the ink tank 4 and the common ink chamber 13 of the head 1. Accordingly, since the solid particles of the ink stored in the common ink chamber 13 can be made to have a uniform concentration, the ink having a uniform concentration of solid particles can be supplied to the ink chamber 11. As a result, settling of solid particles in the ink in the ink chamber 11 can be further suppressed, and the ink replacement effect by refresh can be enhanced.

  It is desirable to always perform the ink circulation operation by driving the circulation pump 43 regardless of whether the head 1 is in the printing area or the non-printing area. In order to be able to replace the ink with a uniform density, it is preferable to perform at least a refreshing period consisting of a fine vibration operation and a discharge operation.

  As nozzle maintenance means (nozzle maintenance process) for performing maintenance for the recovery of the nozzle 12, a wiping operation (wiping process) for scraping off dirt on the nozzle surface with a blade when the head 1 is present in the non-printing area, nozzle surface It is known to perform a wiping operation (wiping process) that wipes ink by pressing a water-absorbing member such as a cloth onto the liquid droplet ejecting apparatus 100. Can do. In this case, it is preferable that neither the fine vibration operation nor the discharge operation described above is executed during the period in which these nozzle maintenance means (nozzle maintenance process) are executed. In particular, when only the fine vibration operation is performed as the nozzle recovery operation, the meniscus in the nozzle 12 vibrates due to the fine vibration, which may destroy the meniscus during the wiping operation or the wiping operation.

  The droplet ejecting apparatus 100 described above is a line type droplet ejecting apparatus that performs printing in one pass on the surface of the recording material. However, the droplet ejecting apparatus moves the head 1 along the main scanning direction. It is also possible to use a scanning type droplet ejecting apparatus that performs printing by reciprocating.

  FIG. 15 shows an example of such a scanning type droplet ejecting apparatus.

  In the droplet ejecting apparatus 200, the recording medium W is sandwiched between the pair of transport rollers 201 and further transported in the direction indicated by the arrow (sub-scanning direction) by the transport roller 203 that is rotationally driven by the transport motor 202. ing.

  The head 1 is provided between the transport roller 203 and the transport roller pair 201 so as to face the surface of the recording medium W. The head 1 is mounted on the carriage 204 so that the nozzle surface side faces the recording medium W. The carriage 204 is driven by a driving means (not shown) along a guide rail 205 spanned across the width direction of the recording medium W, and a left and right direction (right and left directions) substantially orthogonal to the conveyance direction (sub-scanning direction) of the recording medium W (see FIG. It is provided so as to be capable of reciprocating along the main scanning direction.

  The head 1 scans the surface of the recording medium W left and right as the carriage 204 moves in the main scanning direction, and performs desired printing by ejecting liquid droplets from the nozzles 12 in the course of this scanning movement. It has become.

  In this droplet ejection device 200, both sides of the recording medium W are non-printing areas where there is no print data and printing based on the print data is not performed. In the non-printing area, ink receivers 206 are arranged at positions facing the nozzle surface of the head 1. Therefore, when refreshing is performed when the head 1 comes to the non-printing area, droplets are ejected toward the ink receiver 206. When the droplet velocity detection device 3 shown in FIG. 7 is provided, it may be arranged in the non-printing area on both sides of the recording medium W.

  In the head 1 described above, the partition wall 14 between the adjacent ink chambers 11, 11 is formed by a piezoelectric element as energy applying means, and the ink in the ink chamber 11 is formed as droplets from the nozzle 12 by the deformation operation of the partition wall 14. Although what is ejected is exemplified, the specific structure of the energy applying means for applying energy to the ink in the ink chamber is not limited. For example, a heater is provided in the ink chamber as the energy applying means, bubbles are generated in the ink by energizing the heater, and droplets are ejected from the nozzle by the bursting action of the bubbles. One wall surface may be formed by a vibration plate, the vibration plate may be vibrated by a deformation operation of a piezoelectric element, energy may be applied to the ink in the ink chamber, and droplets may be ejected from the nozzle.

  Further, the head 1 is not limited to the nozzle surface arranged in the vertical direction downward, but may be arranged in the horizontal direction or the oblique direction.

Example 1
As shown in FIG. 15, a scanning type droplet ejection device in which ink receivers are arranged in the non-printing areas on both sides of the recording medium is used, and the dispersion medium and an oxidation having a specific gravity larger than the dispersion medium as solid particles From the head using a UV ink containing titanium (difference in specific gravity between dispersion medium and solid particles: 0.25, content of substance having a vapor pressure higher than water at room temperature: 5%) into the print area of the recording medium. Performs predetermined printing, and every time the head comes to the non-printing area to fold back at the end in the main scanning direction, a fine vibration pulse with a frequency half the droplet ejection frequency at the time of printing is applied and then ejected to the ink receiver A droplet having the same frequency as the frequency was discharged.

  As a result, nozzles were not clogged even after continuous operation for 120 hours or more, and stable operation was possible.

(Comparative Example 1)
Continuous operation was performed under the same conditions as in Example 1 except that only the discharge operation was performed without applying the micro-vibration pulse in the non-printing region.

  As a result, nozzle clogging occurred in the ink chamber at the end in 5 hours from the operation.

(Comparative Example 2)
Continuous operation was performed under the same conditions as in Example 1 except that only the fine vibration pulse was applied in the non-printing region and the discharging operation was not performed.

  As a result, nozzle clogging occurred in the ink chamber at the end in 5 hours from the operation.

(Example 2)
As shown in FIG. 1, a line type liquid droplet ejection device that performs printing in one pass from a head is used on the surface of a ceramic tile conveyed by a conveyor belt, and a dispersion medium, yellow pigment particles as solid particles, and From a head using an oil ink (specific gravity difference between a dispersion medium and solid particles: 0.30, content of a substance having a vapor pressure larger than water at room temperature: 3%) in a print area on the surface of the ceramic tile. Was printed. Oil ink for ceramic tiles has a high density and pigment particles tend to settle, so every time the head comes to the non-printing area between ceramic tiles, a fine vibration pulse with the same frequency as the droplet ejection frequency at the time of printing is applied. After that, droplets having the same frequency as the ejection frequency were discharged to the ink receiver.

  As a result, nozzles were not clogged even after continuous operation for 120 hours or more, and stable operation was possible.

(Comparative Example 3)
Continuous operation was performed under the same conditions as in Example 2 except that only the discharge operation was performed without applying the micro-vibration pulse in the non-printing region.

  As a result, nozzle clogging occurred in the ink chamber at the end in 5 hours from the operation.

DESCRIPTION OF SYMBOLS 1: Head 11: Ink chamber 12: Nozzle 13: Common ink chamber 14: Partition 15: Nozzle plate 2: Conveyor belt 2a: Conveying surface 3: Droplet velocity detection device 31: Light projecting unit 32: Light receiving unit 4: Ink tank 41: Supply pipe 42: Return pipe 43: Circulation pump 100: Droplet ejection device 101: CPU
DESCRIPTION OF SYMBOLS 102: Print data memory 103: Encoder 104: Belt conveyance motor 105: Head driver 106: Drive pulse generation part 107: Fine vibration control part 108: Discharge control part 200: Droplet injection apparatus 201: Conveyance roller pair 202: Conveyance motor 203: Transport roller 204: Carriage 205: Guide rail 206: Ink tray P1: Ejection pulse P2: Large droplet ejection pulse C: Ceramic tile L: Detection light W: Recording medium a: Droplet

Claims (22)

An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a droplet ejection device having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
When the head is present in a non-printing area where the printing is not performed, a micro-vibration operation for applying the plurality of micro-vibration pulses to the energy application unit, and a plurality of the energy application unit after the micro-vibration operation are performed. A droplet ejecting apparatus comprising: a refresh unit that applies the ejection pulse and performs a discharge operation for ejecting a droplet amount equal to or larger than a volume of the ink chamber from the nozzle. A droplet velocity detecting means for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
2. The droplet ejection apparatus according to claim 1, wherein the refresh unit is executed after it is detected that the detection result of the droplet velocity detection unit is below a preset threshold value. A pause period detecting means for detecting a period during which ejection of liquid droplets from the nozzle is paused when the head is present in a print area where the print is performed;
2. The liquid droplet ejection apparatus according to claim 1, wherein the refresh unit is executed after it is detected that the detection result of the pause period detection unit exceeds a preset threshold value. An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a droplet ejection device having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
Fine vibration means for performing only a fine vibration operation for applying a plurality of the fine vibration pulses to the energy applying means;
A micro-vibration operation in which a plurality of micro-vibration pulses are applied to the energy application unit, and a plurality of ejection pulses are applied to the energy application unit after the micro-vibration operation, and the volume of the ink chamber is equal to the nozzle. A refresh means for performing a discharging operation for ejecting the above-mentioned droplet amount;
A droplet ejecting apparatus comprising: a selection unit that selects and executes either the fine vibration unit or the refresh unit when the head is in a non-printing area where the printing is not performed. A droplet velocity detecting means for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
After the detection means detects that the detection result of the droplet velocity detection means falls below a preset threshold, either the fine vibration means or the refresh means is selected according to the detection result. The droplet ejection apparatus according to claim 4, wherein the droplet ejection apparatus is selected and executed. A pause period detecting means for detecting a period during which ejection of liquid droplets from the nozzle is paused when the head is present in a print area where the print is performed;
The selection means detects either the fine vibration means or the refresh means according to the detection result after it is detected that the detection result of the droplet velocity detection means exceeds a preset threshold value. The droplet ejection apparatus according to claim 4, wherein the droplet ejection apparatus is selected and executed.   The droplet according to any one of claims 1 to 6, wherein, in the fine vibration operation, the applied frequency is increased as the specific gravity increases in accordance with the specific gravity of the solid particles with respect to the dispersion medium. Injection device. An ink tank for storing the ink to be supplied to the head;
A circulation means for circulating the ink between the head and the ink tank;
The droplet ejecting apparatus according to claim 1, wherein the circulation unit circulates the ink at least during a period in which the refresh unit is executed. When the head is present in a non-printing area where the printing is not performed, at least one of a wiping operation for scraping off dirt on the nozzle surface opened by the nozzle with a blade or a wiping operation for wiping ink on the nozzle surface Having nozzle maintenance means for performing
9. The droplet ejection apparatus according to claim 1, wherein neither the fine vibration unit nor the refresh unit is executed during a period in which the nozzle maintenance unit is being executed.   The droplet ejecting apparatus according to claim 1, wherein the ink has a specific gravity difference of 0.2 or more between the dispersion medium and the solid particles.   The droplet ejecting apparatus according to claim 1, wherein the ink does not volatilize from the nozzles by drying. An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a method for recovering a nozzle of a droplet ejection apparatus having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
When the head is present in a non-printing area where the printing is not performed, a micro-vibration operation for applying the plurality of micro-vibration pulses to the energy application unit, and a plurality of the energy application unit after the micro-vibration operation are performed. A method for recovering a nozzle of a droplet ejection apparatus, comprising: a refresh step of applying the ejection pulse and performing a discharge operation for ejecting a droplet amount equal to or greater than the volume of the ink chamber from the nozzle. A droplet velocity detecting step for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
13. The nozzle recovery method for a droplet ejection device according to claim 12, wherein the refreshing step is executed after it is detected that the detection result of the droplet velocity detection step is below a preset threshold value. . A pause period detecting step of detecting a period in which the ejection of droplets from the nozzle is paused when the head is present in the print area where the print is performed;
13. The nozzle recovery method for a droplet ejection device according to claim 12, wherein the refreshing step is executed after it is detected that the detection result of the pause period detection step exceeds a preset threshold value. An ink chamber to which ink is supplied; a nozzle provided corresponding to the ink chamber; and an energy applying unit configured to apply energy to the ink in the ink chamber by applying a driving pulse, and the nozzle A head for performing printing based on print data in a print area of a recording material by ejecting liquid droplets from
Drive pulse generating means for generating, as the drive pulse, an ejection pulse for ejecting a droplet from the nozzle, and a micro-vibration pulse for causing micro-vibration to the ink in the ink chamber to the extent that the droplet is not ejected from the nozzle; In a method for recovering a nozzle of a droplet ejection apparatus having
The ink comprises a dispersion medium and solid particles having a specific gravity greater than that of the dispersion medium,
A micro-vibration step of performing only a micro-vibration operation of applying a plurality of micro-vibration pulses to the energy applying means;
A micro-vibration operation in which a plurality of micro-vibration pulses are applied to the energy application unit, and a plurality of ejection pulses are applied to the energy application unit after the micro-vibration operation, and the volume of the ink chamber is equal to the nozzle. A refreshing step for performing a discharge operation for ejecting the above droplet amount,
A nozzle recovery method for a droplet ejection apparatus, wherein when the head exists in a non-printing area where the printing is not performed, either the fine vibration process or the refreshing process is selected and executed. A droplet velocity detecting step for detecting a velocity of a droplet ejected from the nozzle when the head exists in a non-printing area where the printing is not performed;
After detecting that the detection result of the droplet velocity detection step is below a preset threshold value, either the fine vibration step or the refresh step is selected and executed according to the detection result. The nozzle recovery method for a droplet ejection apparatus according to claim 15. A pause period detecting step of detecting a period in which the ejection of droplets from the nozzle is paused when the head is present in the print area where the print is performed;
After detecting that the detection result of the pause period detection step exceeds a preset threshold value, either the fine vibration step or the refresh step is selected and executed according to the detection result The nozzle recovery method for a droplet ejection apparatus according to claim 15.   The droplet according to any one of claims 12 to 17, wherein in the fine vibration operation, the applied frequency is increased as the specific gravity increases according to the specific gravity of the solid particles with respect to the dispersion medium. Nozzle recovery method for injection device. An ink tank for storing the ink to be supplied to the head;
19. The nozzle recovery method for a droplet ejection apparatus according to claim 12, wherein the ink is circulated between the head and the ink tank at least during a period in which the refresh process is performed. . When the head exists in a non-printing area where the printing is not performed, at least one of a wiping step of scraping off dirt on the nozzle surface opened by the nozzle with a blade or a wiping step of wiping off ink on the nozzle surface Has a nozzle maintenance process to perform that process,
20. The method for recovering a nozzle of a droplet ejection apparatus according to claim 12, wherein neither the fine vibration process nor the refresh process is executed during a period in which the nozzle maintenance process is executed.   21. The nozzle recovery method for a droplet ejection apparatus according to claim 12, wherein the ink has a specific gravity difference of 0.2 or more between the dispersion medium and the solid particles. The method for recovering a nozzle of a droplet ejection apparatus according to any one of claims 12 to 21, wherein the ink does not volatilize from the nozzle by drying.

Images