Liquid discharge device

Abstract

To provide a liquid discharge device that can easily suppress mixing of a foreign matter in liquid.SOLUTION: A liquid discharge device is provided with: a discharge head that discharges liquid; a liquid supply flow path through which the liquid is supplied to the discharge head; an ultrasonic generating part comprising an ultrasonic element that transmits ultrasonic in a first direction crossing a flowing direction of liquid through the liquid supply flow path; and a branching flow path branching in the flowing direction and a second direction crossing the first direction, from a position where the ultrasonic is transmitted in the liquid supply flow path. The ultrasonic generating part generates gradient of acoustic radiation force by which acoustic radiation force becomes larger, from the liquid supply flow path toward the branching flow path.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device. [Background technology]

[0002] BACKGROUND ART Conventionally, in a liquid ejection device that ejects a liquid, a mesh filter is sometimes disposed in a liquid supply path in order to remove foreign matter contained in the liquid to be ejected (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-169200 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a mesh filter is provided in the supply path of a liquid ejection device, if the filter becomes clogged, the liquid cannot flow easily, and the filter must be replaced, which poses problems such as the effort and cost involved in replacing the filter. [Means for solving the problem]

[0005] A liquid ejection device according to a first aspect of the present disclosure includes an ejection head that ejects liquid, a liquid supply flow path that supplies the liquid to the ejection head, an ultrasonic wave generating unit having an ultrasonic element that transmits ultrasonic waves in a first direction that intersects with a flow direction of liquid in the liquid supply flow path, and a branch flow path that branches off from a position in the liquid supply flow path from which the ultrasonic waves are transmitted in a second direction that intersects with the flow direction and the first direction, and the ultrasonic wave generating unit generates a gradient of acoustic radiation force such that the acoustic radiation force increases from the liquid supply flow path toward the branch flow path. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a liquid ejection apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of a discharge head according to the present embodiment. [Figure 3] FIG. 4 is a cross-sectional view showing a schematic configuration of a foreign matter removal mechanism provided in a liquid supply channel. [Figure 4] 4 is a cross-sectional view showing a schematic configuration of the foreign matter removal mechanism when the foreign matter removal mechanism is cut along line AA in FIG. 3. [Figure 5] 4 is a cross-sectional view showing a schematic configuration of the foreign matter removal mechanism when the foreign matter removal mechanism is cut along line BB in FIG. 3. [Figure 6] FIG. 2 is a schematic plan view showing an example of the ultrasonic element of the present embodiment. [Figure 7] FIG. 7 is a cross-sectional view of the ultrasonic element taken along line CC in FIG. 6. [Figure 8] FIG. 2 is a diagram showing the relationship between an acoustic radiation field and the voltage value of a driving voltage applied to an ultrasonic element. [Figure 9] 10A and 10B are diagrams showing an example of a drag field and an acoustic radiation field in the ultrasonic region of the liquid supply channel in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A liquid ejection device according to an embodiment of the present disclosure will be described below. FIG. 1 is a schematic diagram showing an example of a liquid ejection device 1 according to this embodiment. The liquid ejection device 1 is a device that ejects liquid onto an object, and in this embodiment, an inkjet printer that ejects ink as a liquid onto a medium PP such as printing paper will be described as an example.

[0008] 1, the liquid ejection device 1 includes an ejection head 10, a liquid container 20, a pump 30, a liquid supply channel 40, a reservoir 50, a circulation channel 60, a foreign matter removal mechanism 70, and a control device 80. The control device 80 is, for example, a computer including a processor such as a CPU (Central Processing Unit) and a storage circuit such as a semiconductor memory. The control device 80 controls the operation of each part of the liquid ejection device 1 by having the processor execute a program stored in advance in the storage circuit.

[0009] A liquid is stored in the liquid container 20. The liquid is, for example, an ink in which a pigment is dispersed in a solvent. The liquid is not limited to an ink containing a pigment, but may be an ink containing a dye or an ink containing both a pigment and a dye. The liquid container 20 is, for example, a cartridge that can be attached to and detached from the liquid ejection device 1, a bag-shaped ink pack made of a flexible film, an ink tank that can be refilled with ink, or the like. The liquid container 20 stores a plurality of types of ink of different colors.

[0010] The pump 30 supplies the liquid stored in the liquid container 20 to the ejection head 10. In this embodiment, the pump 30, under the control of the control device 80, can select one of the multiple types of liquid stored in the liquid container 20 and supply it to one ejection head 10. That is, the ejection head 10 of this embodiment can be individually supplied with each of the multiple types of liquid by the control device 80 switching the type of liquid. The pump 30 also recovers the liquid stored in the ejection head 10 via the circulation flow path 60 and returns the recovered liquid to the ejection head 10 via the liquid supply flow path 40.

[0011] The liquid supply flow path 40 is a flow path that connects the pump 30 and the ejection head 10. In the present disclosure, a foreign matter removal mechanism 70 is provided in the liquid supply flow path 40 between the pump 30 and the ejection head 10 to remove foreign matter contained in the liquid. The foreign matter removal mechanism 70 causes the foreign matter to flow into the storage section 50. It is assumed that the flow of the liquid flowing through the liquid supply flow path 40 is a laminar flow. In particular, when the liquid ejection device 1 is an inkjet printer, the flow rate of the liquid (ink) supplied from the liquid container 20 is sufficiently low, and the liquid flows as a laminar flow. Details of the liquid supply flow path 40 and the foreign matter removal mechanism 70 will be described later.

[0012] The reservoir 50 stores foreign matter separated from the liquid supply channel 40 by the foreign matter removal mechanism 70. The reservoir 50 may be provided so as to be detachable from the branch channel 71 of the foreign matter removal mechanism 70. As described above, the circulation flow path 60 is a flow path that returns the liquid inside the ejection head 10 to the liquid supply flow path 40.

[0013] The liquid ejection device 1 of the present disclosure further includes a moving mechanism 91 and a transport mechanism 92. The moving mechanism 91 transports the medium PP in a predetermined direction under the control of the control device 80. The transport mechanism 92 reciprocates the ejection head 10 in a direction intersecting the movement direction of the medium PP under the control of the control device 80. The configurations of the moving mechanism 91 and the transport mechanism 92 are not particularly limited. For example, the moving mechanism 91 may be configured to clamp the medium PP between multiple rollers and move the medium PP by rotating the rollers, or may be configured to feed the medium PP in a predetermined direction by another actuator. Furthermore, the transport mechanism 92 may be configured to move the ejection head 10 by driving an endless belt that holds the ejection head 10, or may be configured to move the ejection head 10, which is held by a support bar so that it can move back and forth, by rotating a screw. The transport direction of the medium PP and the movement direction of the ejection head 10 are not limited to being perpendicular to each other, but may also intersect at a predetermined angle. Furthermore, in this embodiment, any configuration may be used as long as the ejection head 10 is moved relative to the medium PP, and a configuration may be used in which either the medium PP or the ejection head 10 is moved on a two-dimensional plane. Furthermore, the liquid container 20 and the pump 30 may be stored together with the ejection head 10 in a storage case (not shown) and moved together with the ejection head.

[0014] The ejection head 10 ejects liquid from some or all of the multiple nozzles provided therein under the control of the control device 80. In the present disclosure, the ejection direction of the liquid is the direction toward the medium PP. The ejection head 10 ejects liquid from the nozzles while coordinating the transport of the medium PP by the movement mechanism 91 and the reciprocal movement of the ejection head 10 by the transport mechanism 92, causing the liquid to land on the surface of the medium PP. As a result, a desired image is formed on the surface of the medium PP.

[0015] [Detailed configuration of the ejection head 10] Fig. 2 is a diagram showing a schematic configuration of the ejection head 10. The direction of the dashed arrow in Fig. 2 indicates the direction of liquid flow. The ejection head 10 includes a nozzle substrate 11, a communication plate 12, a common liquid chamber forming substrate 13, a pressure chamber substrate 14, a pressure applying plate 15, sealing sheets 161 and 162, and a wiring substrate 18. Here, in the discharge head 10, the discharge direction of the liquid is Z H direction, Z H The direction perpendicular to the X direction H direction, X H Direction and Z H The direction perpendicular to the Y direction H The direction.

[0016] When the medium PP is transported to the printing position, the nozzle substrate 11 H Y H It is a plate-like member arranged so as to be approximately parallel to a plane. Nozzles 111 that function as liquid ejection ports are formed in the nozzle substrate 11. The nozzles 111 are through-holes provided in the nozzle substrate 11. The nozzles 111 may be formed in the shape of a cylinder with an inner circumference parallel to the liquid ejection direction, or may be formed so that the opening diameter narrows along the liquid ejection direction.

[0017] The communication plate 12 is connected to the nozzle substrate 11 via the -Z H The communicating plate 12 is provided on the X side surface. H Y H The communicating plate 12 is a plate-like member arranged substantially parallel to the plane. A plurality of through holes are provided in the communicating plate 12, which form part of an in-head flow path 17 described below. The communicating plate 12 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology.

[0018] The common liquid chamber forming substrate 13 is -Z of the communicating plate 12. H The area surrounded by the common liquid chamber forming substrate 13 and the communication plate 12 forms a first common liquid chamber 171 and a second common liquid chamber 172. HOn the -Z side of the second common liquid chamber 172, a first through-hole 131 is formed penetrating the common liquid chamber forming substrate 13. The first common liquid chamber 171 is connected to the liquid supply flow path 40 via the first through-hole 131. H A second through hole 132 is formed on the side of the common liquid chamber 172. The second common liquid chamber 172 is connected to the circulation flow path 60 via the second through hole 132. The common liquid chamber forming substrate 13 is formed by, for example, injection molding of a resin material.

[0019] The pressure chamber substrate 14 is connected to the -Z H The pressure chamber substrate 14 is a plate-shaped member provided on the surface of the X side. H Y H The pressure chamber substrate 14 is manufactured by processing a single crystal Si substrate using, for example, semiconductor manufacturing technology.

[0020] The pressure applying plate 15 is connected to the pressure chamber substrate 14 at the -Z H The pressure applying plate 15 is a plate-like member provided on the surface of the pressure applying plate 15 on the side of the pressure chamber 173. The pressure applying plate 15 is also a member that can be elastically vibrated. The pressure chambers 173 and 174 are formed by the communicating plate 12, the pressure chamber substrate 14, and the pressure applying plate 15. The pressure chambers 173 and 174 are H The pressure applying plate 15 is a space extending in the axial direction. H Y H The pressure applying plate 15 is arranged so as to be substantially parallel to the plane. H On the side surface, head-side piezoelectric elements PZ1 and PZ2 corresponding to the pressure chambers 173 and 174, respectively, are provided. The head-side piezoelectric elements PZ1 and PZ2 are energy conversion elements that convert electrical energy transmitted from the control device 80 into kinetic energy. The pressure-applying plate 15 is bent by the displacement of the head-side piezoelectric elements PZ1 and PZ2, thereby applying pressure to the liquid in the pressure chambers 173 and 174. The applied pressure causes the liquid to be ejected from the nozzle 111.

[0021] The sealing sheets 161 and 162 are HThe sealing sheets 161 and 162 are provided on the side surfaces of the nozzles 161 and 162. For example, an elastic material is used for the sealing sheets 161 and 162. The sealing sheets 161 and 162 absorb pressure fluctuations of the liquid in the in-head flow path 17, which will be described later.

[0022] The wiring board 18 is connected to the pressure applying plate 15 at -Z. H The wiring board 18 is mounted on the head-side piezoelectric elements PZ1 and PZ2. The wiring board 18 is a component for electrically connecting the control device 80 and the ejection head 10. For example, a flexible wiring board such as a flexible printed circuit (FPC) is used as the wiring board 18. The wiring board 18 supplies drive signals to the head-side piezoelectric elements PZ1 and PZ2 based on control signals from the control device 80.

[0023] Within the ejection head 10, the above-described communicating plate 12, pressure chamber substrate 14, pressure application plate 15, common liquid chamber forming substrate 13, and sealing sheets 161 and 162 form an in-head flow path 17. The in-head flow path 17 is a flow path in the ejection head 10 through which liquid supplied from the liquid supply flow path 40 flows until it is discharged into the circulation flow path 60. One end of the in-head flow path 17 is connected to the liquid supply flow path 40, and the other end is connected to the circulation flow path 60. Specifically, the in-head flow path 17 includes a first common liquid chamber 171, a second common liquid chamber 172, pressure chambers 173 and 174, a nozzle flow path 175, a first connection flow path 176, a second connection flow path 177, a third connection flow path 178, and a fourth connection flow path 179. The first connection flow path 176 is a flow path that connects the first common liquid chamber 171 and the pressure chamber 173. The second connection flow path 177 connects the pressure chamber 174 and the second common liquid chamber 172. The third connection flow path 178 connects the pressure chamber 173 and the nozzle flow path 175. The fourth connection flow path 179 connects the nozzle flow path 175 and the pressure chamber 174. The nozzle flow path 175 has a X H A flow passage extending in the axial direction, X H It is connected to the nozzle 111 near the center in the axial direction.

[0024] In the present disclosure, liquid supplied from the liquid container 20 by the pump 30 is supplied to the first common liquid chamber 171 via the liquid supply channel 40. A portion of the liquid that flows into the first common liquid chamber 171 flows into the pressure chamber 173 via the first connection channel 176. A portion of the liquid that flows into the pressure chamber 173 flows into the pressure chamber 174 via the third connection channel 178, the nozzle channel 175, and the fourth connection channel 179, in this order. A portion of the liquid that flows into the pressure chamber 174 flows through the second connection channel 177 and the second common liquid chamber 172, in this order, before being discharged into the circulation channel 60. The discharged liquid is supplied again by the pump 30 via the liquid supply channel 40 to the first common liquid chamber 171. In this manner, the liquid circulates through the liquid supply channel 40, the ejection head 10, and the circulation channel 60, in this order.

[0025] [Detailed Configuration of the Foreign Matter Removal Mechanism 70 Provided in the Liquid Supply Channel 40] FIG. 3 is a cross-sectional view showing a schematic configuration of a foreign matter removal mechanism 70 provided in the liquid supply channel 40. In FIG. 3, the flow direction of the liquid flowing through the liquid supply channel 40 is the X direction (flow direction in the present disclosure), the direction perpendicular to the X direction is the Z direction (first direction in the present disclosure), and the direction perpendicular to the X direction and the Z direction is the Y direction (second direction in the present disclosure). FIG. 4 is a cross-sectional view showing a schematic configuration of the foreign matter removal mechanism 70 when the foreign matter removal mechanism 70 is cut along line AA in FIG. 3. FIG. 5 is a cross-sectional view showing a schematic configuration of the foreign matter removal mechanism 70 when the foreign matter removal mechanism 70 is cut toward the front side of the page along line BB in FIG. 3. In FIG. 3, black dots represent foreign matter or bubbles in the liquid, and white circles represent coloring materials. 3 and 5, the foreign matter removal mechanism 70 includes a branch flow path 71 that branches in the Y direction from the liquid supply flow path 40, which circulates the liquid in the X direction. This branch flow path 71 is connected to a storage unit 50, and foreign matter in the liquid is stored in the storage unit 50 via the branch flow path 71. Note that, although an example in which the branch flow path 71 and the storage unit 50 are separate structures is shown in this embodiment, a structure in which a part of the branch flow path 71 serves as the storage unit 50 may also be used.

[0026] Furthermore, the foreign matter removal mechanism 70 includes an ultrasonic wave generating unit 72 that transmits ultrasonic waves from the liquid supply channel 40 to a part of the branch channel 71 at the connection between the liquid supply channel 40 and the branch channel 71. The ultrasonic wave generating unit 72 includes an ultrasonic element 73 that transmits ultrasonic waves to the liquid flowing through the liquid supply channel 40 and the branch channel 71, and a drive circuit 74 (see FIGS. 4 and 5) that outputs a drive voltage for transmitting ultrasonic waves to the ultrasonic element 73.

[0027] As shown in FIGS. 4 and 5, the ultrasonic element 73 is provided across from the wall surface 41 on the −Z side of the liquid supply channel 40 to the wall surface 711 on the −Z side of the branch channel 71. More specifically, the ultrasonic element 73 is positioned at least from the −Y side end of the −Z side wall surface 41 of the liquid supply channel 40 (the corner with the −Y side wall surface 42: see FIGS. 3 and 5) to a predetermined distance L from the connection position between the liquid supply channel 40 and the branch channel 71. Y2 The ultrasonic element 73 is provided over a range of width L that covers at least the area between a wall surface 712A (see FIG. 3) on the −X side of the branch flow path 71 and a wall surface 712B (see FIG. 3) on the +X side of the −Z side of the branch flow path 71. X It is set in the range of. 3, when viewed from the Z direction, the region of the liquid supply channel 40 and the branch channel 71 that overlaps with the ultrasonic element 73 becomes an ultrasonic region 730 through which ultrasonic waves transmitted from the ultrasonic element 73 propagate. Furthermore, of the ultrasonic region 730, the portion that overlaps with the liquid supply channel 40 is referred to as a first region 730A, and the portion that overlaps with the branch channel 71 is referred to as a second region 730B.

[0028] FIG. 6 is a schematic plan view showing an example of the ultrasonic element 73 of this embodiment, and FIG. 7 is a cross-sectional view of the ultrasonic element 73 taken along line CC in FIG. As shown in FIG. 6, the ultrasonic element 73 has a plurality of ultrasonic transducers Tr arranged in a two-dimensional array along the X and Y directions. For ease of explanation, FIG. 6 shows a reduced number of ultrasonic transducers Tr, but in reality, more ultrasonic transducers Tr may be arranged.

[0029] As shown in FIG. 7, the ultrasonic element 73 is configured to include an element substrate 731, a vibration plate 732 provided on the element substrate 731, and a piezoelectric element 733 provided on the vibration plate 732. The element substrate 731 is made of a semiconductor substrate such as Si. Substrate openings 731A corresponding to the respective ultrasonic transducers Tr are provided in this element substrate 731. In this embodiment, each substrate opening 731A is a through-hole that penetrates the element substrate 731 in the substrate thickness direction (Z direction), and the vibration plate 732 is provided on the -Z side of the through-hole.

[0030] The diaphragm 732 is made of, for example, a laminate of SiO2 and ZrO2, and is provided so as to cover the entire -Z side of the element substrate 731. That is, the diaphragm 732 is supported by the partition wall 731B that forms the substrate opening 731A, and closes the -Z side of the substrate opening 731A. The thickness of the diaphragm 732 is sufficiently smaller than that of the element substrate 731.

[0031] Piezoelectric elements 733 are provided on vibration plates 732 that close each substrate opening 731A. Piezoelectric elements 733 are each formed of a laminate in which a lower electrode 733A, a piezoelectric film 733B, and an upper electrode 733C are laminated from vibration plate 732 toward the -Z side. Here, the portion of the vibration plate 732 that closes the substrate opening 731A constitutes the vibration part 732A, and one ultrasonic transducer Tr is constituted by this vibration part 732A and the piezoelectric element 733. In addition, the +Z side surface of the vibration part 732A becomes the liquid contact surface that comes into contact with the liquid in the liquid supply channel 40 or the branch channel 71. In such an ultrasonic transducer Tr, when a rectangular wave voltage (drive signal) of a predetermined frequency is applied between the lower electrode 733A and the upper electrode 733C, the piezoelectric film 733B bends, and the vibrating part 732A vibrates in the Z direction, which is the normal direction of the liquid contact surface, and ultrasonic waves are emitted to the +Z side.

[0032] In this embodiment, for example, the lower electrodes 733A of the ultrasonic transducers Tr arranged in the Y direction are connected to each other. As shown in Fig. 6, these lower electrodes 733A are connected to a common terminal 734. The common terminal 734 is electrically connected to the drive circuit 74 via, for example, a flexible printed circuit board or the like, and applies a reference potential to each lower electrode 733A.

[0033] In addition, the upper electrodes 733C of the ultrasonic transducers Tr arranged in the X direction are connected to each other. Here, the region where the ultrasonic transducers Tr are arranged facing the first region 730A is referred to as the first element region Ar1, and the region where the ultrasonic transducers Tr are arranged facing the second region 730B is referred to as the second element region Ar2. The upper electrodes 733C of each ultrasonic transducer Tr arranged in the first element region Ar1 are connected to a first drive terminal 735A, and this first drive terminal 735A is electrically connected to the drive circuit 74 via, for example, a flexible printed circuit board or the like. In addition, the upper electrodes 733C of each ultrasonic transducer Tr arranged in a position (second region 730B) facing the branch flow path 71 are connected to a second drive terminal 735B, and this second drive terminal 735B is electrically connected to the drive circuit 74 via, for example, a flexible printed circuit board or the like.

[0034] The drive circuit 74 functions as the radiation force adjustment unit of the present disclosure, and includes a reference potential circuit 741, a first drive circuit 742, and a second drive circuit 743, as shown in FIG. The reference potential circuit 741 applies a reference potential to the lower electrode 733A of each ultrasonic transducer Tr via the common terminal 734. The first drive circuit 742 applies a first drive voltage to the upper electrode 734A of the ultrasonic transducer Tr facing the first region 730A via the first drive terminal 735A. The second drive circuit 743 applies a second drive voltage to the upper electrode 734A of the ultrasonic transducer Tr facing the second region 730B via the second drive terminal 735B.

[0035] The drive circuit 74 controls the drive frequencies of the first drive voltage and the second drive voltage output from the first drive circuit 742 and the second drive circuit 743 under the control of the control device 80. This generates standing waves in the first region 730A and the second region 730B. Furthermore, the drive circuit 74 controls the voltage values ​​of the first drive voltage and the second drive voltage output from the first drive circuit 742 and the second drive circuit 743 under the control of the control device 80. This causes the acoustic radiation force due to the standing wave formed in the first region 730A to differ from the acoustic radiation force due to the standing wave formed in the second region 730B. Specifically, the drive circuit 74 controls the voltage values ​​of the first drive voltage and the second drive voltage output from the first drive circuit 742 and the second drive circuit 743 so that the acoustic radiation force in the second region 730B is greater than that in the first region 730A.

[0036] [Functional configuration of the control device 80] As described above, the control device 80 includes a processor and a memory circuit, and when the processor executes a program stored in the memory circuit, the control device 80 functions as a frequency determination unit 81, a colorant identification unit 82, an acoustic radiation force determination unit 83, and the like, as shown in Fig. 5. The control device 80 also performs drive control (liquid discharge control) of the head-side piezoelectric elements PZ1 and PZ2 of the discharge head 10, drive control of the moving mechanism 91 and the transport mechanism 92, and drive control of the pump 30, but in this embodiment, a description of these controls will be omitted.

[0037] The frequency determination unit 81 determines a frequency for forming a standing wave in the ultrasonic region 730 . The frequency determination unit 81 sweeps the frequency of the ultrasonic waves output from each ultrasonic transducer Tr in the first element region Ar1 facing the first region 730A, and measures the impedance between the common terminal 834 and the first drive terminal 835A (the impedance related to the first element region Ar1).The frequency at which the impedance takes a maximum value is then identified as the frequency at which a standing wave is formed.The same applies to the frequency of the ultrasonic waves output from each ultrasonic transducer Tr in the second element region Ar2 facing the second region 730B. In addition, when the flow path width in the Z direction of the liquid supply flow path 40 and the branch flow path 71 is constant, a fixed frequency corresponding to the flow path width may be used as the frequency that forms the standing wave.

[0038] The colorant specifying unit 82 specifies fine particles (colorant in this embodiment) in the liquid that are not to be captured. In this embodiment, the foreign matter removal mechanism 70 uses the gradient of the acoustic radiation force of the ultrasonic waves to move the particles from the liquid supply channel 40 to the branch channel 71. By increasing the drive voltage applied to the ultrasonic element 73, it is possible to output ultrasonic waves with a large acoustic radiation force. However, if the acoustic radiation force is too large, the foreign matter removal mechanism 70 may remove the coloring material output from the nozzle 111 together with the liquid. In this embodiment, the colorant identification unit 82 identifies particles to be captured and particles not to be captured. Specifically, it identifies colorant information of the liquid contained in the liquid container 20 set in the liquid ejection device 1. The colorant identification unit 82 may identify the colorant information based on data entered by the user. Alternatively, the liquid container 20 may have a data chip on which the colorant information is written, and when the liquid container 20 is set in the liquid ejection device 1, the colorant information may be obtained by reading the information from the data chip. The data chip may be, for example, a magnetic storage device, a semiconductor memory, or code data such as a QR code (registered trademark).

[0039] The acoustic radiation force determination unit 83 determines the drive voltage value of the ultrasonic waves to be output from the ultrasonic elements 73 based on the colorant information, and outputs a control signal to the drive circuit 74. At this time, the voltage values ​​are set so that the voltage value of the first drive voltage output from the first drive circuit 742 is smaller than the voltage value of the second drive voltage output from the second drive circuit 743, and so that the colorant is not trapped in the first region 730A, but other particles (foreign matter, air bubbles) with a diameter equal to or larger than the particle diameter of the colorant are trapped and moved. The voltage value of the first drive voltage corresponding to the colorant information may be stored in advance in a memory circuit.

[0040] [Particle removal principle] Next, the principle of particle removal in this embodiment will be described. In this embodiment, the liquid flowing through the liquid supply channel 40 is a laminar flow as described above, and in this case, a force due to the flow of the liquid (hereinafter referred to as a drag force) acts on the particles in the liquid along the X direction. The drag force acting on the particles becomes smaller as the flow velocity of the liquid decreases. Furthermore, the drag force acting on the particles becomes smaller as the size of the particles decreases. On the other hand, when ultrasonic waves are transmitted into a liquid, the acoustic radiation force of the ultrasonic waves acts on the particles. The acoustic radiation force acting on the particles is affected by the physical properties (particularly the acoustic impedance) and size of the particles, and is larger the larger the size of the particles and the larger the difference in acoustic impedance between the particles and the liquid.

[0041] FIG. 8 is a diagram showing the relationship between the acoustic radiation field and the voltage value of the drive voltage applied to the ultrasonic element 73. Increasing the voltage value of the drive voltage applied to the ultrasonic element 73 also increases the acoustic radiation force. When ultrasonic waves are transmitted from the ultrasonic generator 72 to the ultrasonic region 730, the energy of the field (acoustic radiation field) due to the acoustic radiation force in the ultrasonic region 730 reaches a minimum value approximately at the center of the ultrasonic region 730, as shown in FIG. 8. In reality, the position where the minimum value is reached shifts downstream (to the +X side) due to the influence of the field (drag field) caused by the flow of the liquid. In this embodiment, the liquid flow rate is sufficiently slow, and the position where the energy of the acoustic radiation field reaches a minimum value in the X direction is within the range where the branch flow path 71 is connected, i.e., within the ultrasonic region 730. In the acoustic radiation field, the particle moves from a position of high energy to a position of low energy, which means that the particle is trapped in the position where the energy in the acoustic radiation field is at a minimum in the X direction, i.e., in the center of the ultrasonic region 730.

[0042] 9 is a diagram showing an example of a drag field and an acoustic radiation field in the ultrasonic region 730 of the liquid supply channel 40. In FIG. 9, line P1 indicates the acoustic radiation field for a foreign substance to be removed in the liquid, and line Q1 indicates the drag field for the foreign substance. Line P2 indicates the acoustic radiation field for an air bubble in the liquid, and line Q2 indicates the drag field for the air bubble. Line P3 indicates the acoustic radiation field for a coloring material in the liquid, and line Q3 indicates the drag field for the coloring material. In the liquid supply channel 40, as described above, the liquid flows in the X direction, and the particles in the liquid are subjected to a force due to the liquid flow. The energy of the drag field due to the force of the liquid flow decreases linearly along the X direction, as shown in Figure 9. In other words, the particles are subjected to a constant force due to the liquid flow, and move from the -X side, which has higher energy, to the +X side, which has lower energy.

[0043] Comparing the acoustic radiation field and the drag field for the coloring material in the ultrasonic region 730, the energy of the acoustic radiation field is lower than the energy of the drag field, which means that the coloring material is less captured by the acoustic radiation force and is swept toward the +X side by the liquid flow.

[0044] Comparing the acoustic radiation field and the drag field for bubbles in the ultrasonic region 730, the energy of the acoustic radiation field exceeds the energy of the drag field on the +X side. In this case, the bubbles are trapped by the acoustic radiation force and are trapped at approximately the center position of the ultrasonic region 730 (the position where the energy is minimum) against the flow of the liquid. In addition, in this embodiment, the ultrasonic element 73 forms a standing wave in the ultrasonic region. Therefore, the bubbles are trapped at the antinode position of the standing wave.

[0045] Comparing the acoustic radiation field and the drag field for a foreign object in the ultrasonic region 730, the energy of the acoustic radiation field exceeds the energy of the drag field on both the ±X side. Therefore, the foreign object is also captured by the acoustic radiation force and is captured at approximately the center position (the position where the energy is minimum) of the ultrasonic region 730. Furthermore, in this embodiment, the foreign object is captured at the node position of the standing wave formed in the ultrasonic region 730.

[0046] Furthermore, in this embodiment, there is a difference in acoustic radiation force between the first region 730A and the second region 730B of the ultrasonic region 730. That is, the acoustic radiation force in the second region 730B of the branch channel 71 is greater than the acoustic radiation force in the first region 730A of the liquid supply channel 40. In the second region 730B where the acoustic radiation force is greater, the energy in the acoustic radiation field is smaller than in the first region 730A where the acoustic radiation force is smaller. Therefore, foreign matter and bubbles captured by the standing wave in the first region 730A move to the second region 730B side, i.e., to the branch channel 71, in accordance with the balance of acoustic radiation forces, and are then flown from the branch channel 71 to the storage section 50.

[0047] As a result, in this embodiment, liquid containing a large amount of foreign matter and air bubbles is removed from the liquid in the liquid supply flow path 40 and moved to the storage section 50. Furthermore, the coloring material is less affected by capture by ultrasonic waves, and is sent to the ejection head 10 along with the flow of liquid in the liquid supply flow path 40.

[0048] [Effects of this embodiment] The liquid ejection device 1 of this embodiment includes an ejection head 10 that ejects liquid, a liquid supply flow path 40 that supplies liquid to the ejection head 10, an ultrasonic wave generating unit 72 equipped with an ultrasonic element 73 that transmits ultrasonic waves in the Z direction, and a branch flow path 71 that branches in the Y direction from the position in the liquid supply flow path 40 where the ultrasonic waves are transmitted. The ultrasonic wave generating unit 72 generates ultrasonic waves from the liquid supply flow path 40 toward the branch flow path 71 so that the acoustic radiation force increases. Therefore, the acoustic radiation force can capture foreign matter and air bubbles in the liquid flowing through the liquid supply channel 40. Furthermore, as the acoustic radiation force increases from the liquid supply channel 40 toward the branch channel 71, the foreign matter and air bubbles move from the liquid supply channel 40 to the branch channel 71 in the Y direction, where the energy is smaller. This makes it possible to reduce the amount of foreign matter and air bubbles contained in the liquid flowing through the liquid supply channel 40, and to prevent clogging of the nozzle 111.

[0049] In the liquid ejection device 1 of this embodiment, the ultrasonic wave generating unit 72 generates a standing wave in the Z direction. This allows foreign matter to be captured by the nodes of the standing waves and air bubbles to be captured by the antinodes of the standing waves, thereby further preventing foreign matter and air bubbles from flowing from the liquid supply channel 40 into the ejection head 10.

[0050] In this embodiment, the ultrasonic generator 72 includes a drive circuit 74, which controls the ultrasonic transducer Tr in the first element region Ar1 of the ultrasonic element 73 and the ultrasonic transducer Tr in the second element region Ar2 of the ultrasonic element 73, respectively, to adjust the acoustic radiation force of the ultrasonic waves along the Y direction. This allows foreign matter captured in the liquid supply channel to be moved toward the branch channel. Also, by simply controlling the drive voltage applied to the first element region Ar1 and the drive voltage applied to the second element region Ar2, a gradient of acoustic radiation force along the Y direction can be easily formed in the ultrasonic region 730.

[0051] In this embodiment, the ultrasonic wave generating unit 72 transmits ultrasonic waves from the liquid supply channel 40 to a part of the branch channel 71 . This allows a gradient of acoustic radiation force to be formed by ultrasound from the liquid supply flow path 40 to a portion of the branch flow path 71, making it easier for foreign matter and air bubbles to move through the branch flow path 71 and suppressing the outflow of foreign matter and air bubbles from the liquid supply flow path 40 to the ejection head 10.

[0052] In this embodiment, the control device 80 functions as a colorant identification unit 82 and an acoustic radiation force determination unit 83. The colorant identification unit 82 identifies the colorant information of the liquid, and the acoustic radiation force determination unit 83 determines the driving voltage value of the ultrasound to be output from the ultrasonic element 73 based on the branch flow path 71 for the identified colorant, i.e., the desired acoustic radiation force. This makes it possible to prevent the color material to be ejected from the nozzles 111 of the ejection head 10 from moving to the branch flow path 71 .

[0053] In this embodiment, the ultrasonic element 73 includes a vibration part 732A having a liquid contact surface that comes into contact with the liquid flowing through the liquid supply channel 40, and a piezoelectric element 733 that flexibly vibrates the vibration part 732A in the Z direction. This allows ultrasonic waves to be propagated directly from the vibrating section 732A to the liquid, and ultrasonic waves with a large acoustic radiation force can be sent to the liquid at a low voltage.

[0054] In this embodiment, the branch flow path 71 is located at a position where the energy becomes a minimum value in the combined field of the drag field caused by the force of the liquid flowing through the liquid supply flow path 40 and the acoustic radiation field caused by the acoustic radiation force of the ultrasound transmitted from the ultrasound generating unit 72. As a result, foreign matter to be moved to the branch channel can be captured at the connection point between the liquid supply channel 40 and the branch channel 71, and can be moved from the liquid supply channel 40 to the branch channel 71 due to the gradient of the acoustic radiation force.

[0055] In this embodiment, the liquid ejection device 1 further includes a circulation flow path 60, one end of which is connected to the ejection head 10 and the other end of which is connected to the liquid supply flow path 40 via a pump 30, and the pump 30 circulates the liquid from the circulation flow path 60 to the liquid supply flow path 40. This allows the liquid to be reused by returning it from the ejection head 10 to the liquid supply flow path 40 via the circulation flow path 60. At this time, even if foreign matter enters from the nozzle 111 of the ejection head 10, the foreign matter can be moved to the branch flow path 71 by the ultrasonic generator 72 provided in the liquid supply flow path 40.

[0056] In this embodiment, the ejection head 10 includes a nozzle 111 that ejects liquid, a pressure chamber 173 that is connected to the nozzle 111 and applies pressure to the liquid, a pressure chamber 174 that is connected to the nozzle 111 and applies pressure to the liquid, a first common liquid chamber 171 that is connected to the pressure chamber 173 and into which liquid flows from the liquid supply flow path 40, and a second common liquid chamber 172 that is connected to the pressure chamber 174 and from which liquid flows out to the circulation flow path 60. As a result, the liquid sent to the ejection head 10 fills the pressure chambers 173 and 174. A portion of the liquid to which pressure is applied in the pressure chamber 173 is ejected from the nozzle 111 and also sent to the pressure chamber 174. A portion of the liquid to which pressure is applied in the pressure chamber 174 flows back toward the nozzle 111 and is ejected from the nozzle 111, and the remainder is sent from the circulation channel 60 to the liquid supply channel 40. With this configuration, the flow rate of the liquid flowing through the ejection head 10, the liquid supply channel 40, and the circulation channel 60 can be slowed down, and the liquid can be circulated in a laminar flow. Therefore, the drag force caused by the flow of the liquid is sufficiently reduced, making it easier to capture foreign matter and air bubbles by the acoustic radiation force.

[0057] [Variations] The present invention is not limited to the above-described embodiments, and the present invention includes configurations obtained by modifications, improvements, and appropriate combinations of the embodiments within the scope that can achieve the object of the present invention.

[0058] [Variation 1] In the above embodiment, an example of forming a standing wave by the ultrasonic element 73 is shown, but the present invention is not limited to this. Forming a standing wave improves the particle capture force at the node or antinode positions, but even if a standing wave is not formed, as described above, particles can be captured by making the energy of the acoustic radiation field equal to or greater than the energy of the drag field.

[0059] [Variation 2] In the above embodiment, an example was shown in which the first drive circuit 742 of the drive circuit 74 adjusts the first drive voltage to be applied to each ultrasonic transducer Tr in the first element region Ar1 of the ultrasonic element 73, and the second drive circuit 743 adjusts the second drive voltage to be applied to each ultrasonic transducer Tr in the second element region Ar2, based on the control of the control device 80. In contrast to this, as a method for making the acoustic radiation force of the second region 730B greater than the acoustic radiation force of the first region 730A, the arrangement density of the ultrasonic transducers Tr in the second element region Ar2 may be made greater than the arrangement density of the ultrasonic transducers Tr in the first element region Ar1. Alternatively, as in the above embodiment, an ultrasonic element 73 may be arranged extending from the liquid supply channel 40 to a portion of the branch channel 71, and a second ultrasonic element may be arranged on the +Z side surface of the branch channel 71 corresponding to the second region 730B of the branch channel 71. That is, ultrasonic waves are emitted from the first element region Ar1 to the first region 730A, and ultrasonic waves are emitted from the second element region Ar2 and the second ultrasonic element to the second region 730B. This makes it possible to increase the acoustic radiation force in the second region 730B compared to the acoustic radiation force in the first region 730A.

[0060] [Variation 3] In the above embodiment, an example was shown in which the liquid sent to the ejection head is returned to the liquid supply flow path 40 via the circulation flow path 60, but this is not limiting. A configuration may be adopted in which the circulation flow path 60 is not provided, or a recovery unit that recovers the liquid may be provided instead of the circulation flow path 60.

[0061] [Variation 4] In the above embodiment, the ultrasonic element 73 has a first element region Ar1 and a second element region Ar2, and a configuration in which different drive voltages are applied to these two regions has been exemplified, but this is not limiting. The ultrasonic element 73 may also have three or more element regions, and these element regions may be arranged in the Y direction. Furthermore, ultrasonic transducers Tr arranged in the X direction may be treated as one channel, and each channel may be individually drivable. In this case, the drive voltage to each element region may be changed so that the acoustic radiation force gradually increases from the -Y side toward the +Y side.

[0062] [Summary of the present invention] A liquid ejection device according to a first aspect of the present disclosure comprises an ejection head that ejects liquid, a liquid supply flow path that supplies the liquid to the ejection head, an ultrasonic wave generating unit having an ultrasonic element that transmits ultrasonic waves in a first direction that intersects the flow direction of the liquid in the liquid supply flow path, and a branch flow path that branches off from a position in the liquid supply flow path from which the ultrasonic waves are transmitted in a second direction that intersects the flow direction and the first direction, and the ultrasonic wave generating unit generates the ultrasonic waves so that the acoustic radiation force increases from the liquid supply flow path towards the branch flow path. This allows foreign matter in the liquid to be moved from the liquid supply circuit to the branch flow path by the acoustic radiation force, making it possible to easily prevent foreign matter from being mixed into the liquid flowing to the ejection head.

[0063] In the liquid ejection device of the present disclosure, it is preferable that the ultrasonic wave generating section generates a standing wave in the first direction. This allows foreign matter and air bubbles to be captured by the nodes or antinodes of the standing waves, thereby further suppressing the inflow of foreign matter and air bubbles into the liquid supply channel.

[0064] In the liquid ejection device of the present disclosure, the ultrasonic wave generating unit preferably includes a radiation force adjusting unit that adjusts the acoustic radiation force of the ultrasonic waves along the second direction. This allows the foreign matter captured in the liquid supply flow path to be moved toward the branch flow path.

[0065] In the liquid ejection device of the present disclosure, the ultrasonic elements are arranged in multiple positions along the second direction, and the radiation force adjustment unit adjusts the acoustic radiation force by adjusting the voltages applied to the multiple ultrasonic elements lined up in the second direction, respectively. This makes it possible to easily form a gradient of the acoustic radiation force along the second direction by driving each of the ultrasonic elements arranged along the second direction.

[0066] In the liquid ejection device of the present disclosure, the ultrasonic wave generating unit transmits the ultrasonic wave from the liquid supply channel to a part of the branch channel. This allows a gradient of acoustic radiation force to be formed by ultrasonic waves from the liquid supply channel to a portion of the branch channel, making it easier for foreign matter to move into the branch channel.

[0067] In the liquid ejection device of the present disclosure, the radiation force adjustment unit adjusts the acoustic radiation force based on the size of the particles to be flowed into the branch flow channel or the physical properties of the particles. This makes it possible to prevent the fine particles that are intended to flow from the liquid supply flow path to the ejection head from flowing into the branch flow path.

[0068] In the liquid ejection device of the present disclosure, the ultrasonic element includes a vibration part having a liquid contact surface that comes into contact with the liquid flowing through the liquid supply channel, and a piezoelectric element that causes the vibration part to flexibly vibrate in the normal direction to the liquid contact surface. This allows ultrasonic waves to be propagated directly from the vibrating section to the liquid, and ultrasonic waves with a large acoustic radiation force can be transmitted to the liquid at a low voltage.

[0069] In the liquid ejection device of the present disclosure, the branch flow path is located at a position where the energy is at a minimum value in a combined field of a drag field based on the force of the flow of the liquid flowing through the liquid supply flow path and an acoustic radiation field based on the acoustic radiation force of the ultrasonic waves transmitted from the ultrasonic wave generating unit. This allows foreign matter to be captured at the connection point between the liquid supply channel and the branch channel and moved from the liquid supply channel to the branch channel by the gradient of the acoustic radiation force.

[0070] The liquid ejection device of the present disclosure further includes a circulation flow path having one end connected to the ejection head and the other end connected to the liquid supply flow path via a pump, and the pump sends the liquid from the circulation flow path to the liquid supply flow path. This allows the liquid to be reused by returning it from the ejection head to the liquid supply channel via the circulation channel. In this case, even if foreign matter enters the liquid supply channel from the nozzle of the ejection head, the foreign matter can be moved to the branch channel by the ultrasonic generator provided in the liquid supply channel.

[0071] In the liquid ejection device of the present disclosure, the ejection head includes a nozzle that ejects the liquid, a first pressure chamber connected to the nozzle and that applies pressure to the liquid, a second pressure chamber connected to the nozzle and that applies pressure to the liquid, a first common liquid chamber connected to the first pressure chamber and into which the liquid flows from the liquid supply flow path, and a second common liquid chamber connected to the second pressure chamber and that causes the liquid to flow out into the circulation flow path. As a result, the liquid sent to the ejection head fills the first pressure chamber and the second pressure chamber. A portion of the liquid pressurized in the first pressure chamber is ejected from the nozzle and sent to the second pressure chamber. A portion of the liquid pressurized in the second pressure chamber flows back toward the nozzle and is ejected from the nozzle, and the remainder is sent from the circulation flow path to the liquid supply flow path. With this configuration, the flow rate of the liquid flowing through the ejection head, liquid supply flow path, and circulation flow path can be slowed, and the liquid can be circulated in a laminar flow. Therefore, even if the acoustic radiation force of the ultrasonic waves generated by the ultrasonic generator is small, the foreign matter capture force due to the acoustic radiation force is greater than the drag force due to the liquid flow, and the foreign matter can be suitably moved to the branch flow path. [Explanation of symbols]

[0072] 1...liquid ejection device, 10...ejection head, 30...pump, 40...liquid supply flow path, 41, 42, 711, 712A, 712B...wall surface, 50...storage section, 60...circulation flow path, 70...foreign matter removal mechanism, 71...branch flow path, 72...ultrasonic wave generating section, 73...ultrasonic element, 74...driving circuit, 80...controller, 81...frequency determining section, 82...colorant identifying section, 83...acoustic radiation force determining section, 730...ultrasonic region, 730A...first region, 730B...second region, 731...element substrate, 732...vibration plate, 732A...vibrating section, 733...piezoelectric element, 741...reference potential circuit, 742...first driving circuit, 743...second driving circuit.

Claims

1. a discharge head that discharges liquid; a liquid supply flow path that supplies the liquid to the ejection head; an ultrasonic wave generating unit including an ultrasonic element that transmits ultrasonic waves in a first direction that intersects with a flow direction of the liquid in the liquid supply channel; a branch flow path branching from a position of the liquid supply flow path from which the ultrasonic waves are transmitted in a second direction intersecting the flow direction and the first direction; Equipped with The ultrasonic wave generating unit generates the ultrasonic waves so that an acoustic radiation force increases from the liquid supply channel toward the branch channel.

2. The ultrasonic wave generating unit generates a standing wave in the first direction. The liquid ejection device according to claim 1 .

3. the ultrasonic wave generator includes a radiation force adjuster that adjusts an acoustic radiation force of the ultrasonic waves along the second direction. The liquid ejection device according to claim 1 .

4. The ultrasonic elements are arranged in plurality along the second direction, the radiation force adjustment unit adjusts the acoustic radiation force by adjusting voltages applied to the plurality of ultrasonic elements arranged in the second direction, respectively. The liquid ejection device according to claim 3 .

5. the ultrasonic wave generating unit transmits the ultrasonic wave from the liquid supply channel to a part of the branch channel. The liquid ejection device according to claim 3 .

6. the radiation force adjusting unit adjusts the acoustic radiation force based on the size of the particles to be flowed into the branch flow path or the physical properties of the particles. The liquid ejection device according to claim 3 .

7. the ultrasonic element includes a vibration part having a liquid contact surface that comes into contact with the liquid flowing through the liquid supply channel, and a piezoelectric element that flexibly vibrates the vibration part in a direction normal to the liquid contact surface. The liquid ejection device according to claim 1 .

8. the branch flow path is provided at a position where energy becomes a minimum value in a combined field of a drag field based on the force of the flow of the liquid flowing through the liquid supply flow path and an acoustic radiation field based on the acoustic radiation force of the ultrasonic waves transmitted from the ultrasonic generator. The liquid ejection device according to claim 1 .

9. a circulation flow path having one end connected to the ejection head and the other end connected to the liquid supply flow path via a pump; The pump sends the liquid from the circulation channel to the liquid supply channel. The liquid ejection device according to claim 1 .

10. The ejection head includes: a nozzle for ejecting the liquid; a first pressure chamber connected to the nozzle and configured to apply pressure to the liquid; a second pressure chamber connected to the nozzle and configured to apply pressure to the liquid; a first common liquid chamber connected to the first pressure chamber and into which the liquid flows from the liquid supply channel; a second common liquid chamber connected to the second pressure chamber and allowing the liquid to flow into the circulation channel; The liquid ejection device of claim 9 , comprising:

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