Ultrasonic irradiation device

Abstract

To provide a device capable of further uniformly applying ultrasonic waves to a large number of objects (for example, seeds) in a liquid in a container.SOLUTION: Ultrasonic transducers 110A to 110D are provided at positions respectively deviated from central axes L0 and L1 of respective lateral faces of a water tank 100 and rotationally symmetric with respect to a center O of a horizontal plane shape (a square) of the water tank 100. When ultrasonic waves are applied into the water tank 100 from the ultrasonic transducers 110A to 110D, a flow rotating clockwise around the center O is generated. Objects such as seeds floating in or on a surface of water 200 in the water tank 100 circulate in the water tank 100 on the rotating flow. The objects receive the ultrasonic waves from the ultrasonic transducers 110A to 110D from various directions at various positions in the circulating movement.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an ultrasonic irradiation device. [Background technology]

[0002] It is known that exposure of plant seeds to ultrasound improves their germination rate and subsequent growth rate.

[0003] For example, Patent Document 1 describes that the germination rate can be improved by placing seeds in a water tank, immersing them in hot water, and irradiating them with ultrasound.

[0004] Furthermore, Patent Document 2 discloses that germination and growth after germination are promoted by irradiating seeds in a liquid such as water with ultrasound while stirring the seeds with a magnetic stirring bar (see, for example, FIG. 6, paragraph 0043).

[0005] The effect of ultrasound differs between the side of the seed that is exposed to ultrasound and the side that is not. It is considered desirable to irradiate the entire surface of the seed with ultrasound as uniformly as possible, but it is difficult to irradiate the entire surface uniformly with ultrasound simply from one direction.

[0006] When multiple seeds are irradiated, the seeds closest to the ultrasonic transducer receive stronger ultrasound. However, the ultrasound is blocked or scattered by the seeds, so the ultrasound received by the seeds further away is weaker. Thus, the intensity of the irradiated ultrasound varies depending on the position of each seed. Such variation in irradiation intensity is often undesirable in both experiments and industrial applications.

[0007] In addition, for example, in a configuration in which ultrasonic waves are emitted upward from a transducer fixed to the bottom of a water tank, standing waves are generated along the depth direction due to interference with the reflected waves from the water surface. Since seeds floating in the water tend to gather in areas with low sound pressure, when standing waves are generated, seed clusters are formed at the height of the nodes of the standing waves. If there is no mechanism to stir these seed clusters, the intensity of ultrasonic irradiation will differ between the seeds in the cluster close to the transducer and the seeds above that cluster.

[0008] In Patent Document 2, the seeds are stirred with a magnetic stirring bar, thereby reducing the variation in ultrasonic irradiation intensity for a large number of seeds.

[0009] In the field of ultrasonic cleaning, various methods have been proposed to make the sound field in a water tank uniform (see, for example, Patent Documents 3 to 5). However, all of these techniques are intended to clean objects that are much larger than the wavelength of the ultrasonic waves. When irradiating objects smaller than the wavelength of the ultrasonic waves, such as seeds, it is not always possible to irradiate the entire surface of each seed or a large number of seeds uniformly using the same method.

[0010] Patent Document 6 discloses an apparatus for reducing the positional variation in ultrasonic intensity caused by the influence of standing waves in a biological tissue container to which ultrasonic waves are irradiated. In this apparatus, the generation of standing waves is suppressed by randomly changing the initial phase of a drive signal for driving an ultrasonic generator. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 63-56205 [Patent Document 2] Special Publication No. 2015-524250 [Patent Document 3] JP 2009-166028 A [Patent Document 4] JP 2008-141023 A [Patent Document 5] JP 2004-249212 A [Patent Document 6] JP 2015-223109 A Summary of the Invention [Problem to be solved by the invention]

[0012] To deal with the problem of standing waves, a mechanism for mechanically stirring the water in the tank would make the device more complicated and increase costs. In addition, a method for suppressing the generation of standing waves by controlling the drive signal of the transducer requires a special control circuit.

[0013] The present invention aims to provide an apparatus that can more uniformly irradiate ultrasonic waves to a large number of objects (e.g., seeds) in a liquid in a container, without using a special drive signal control circuit or a mechanical stirring mechanism for suppressing standing waves. [Means for solving the problem]

[0014] The ultrasonic irradiation device disclosed in this specification comprises a container for holding a liquid containing an object to be irradiated with ultrasonic waves, and one or more ultrasonic transducers for irradiating an ultrasonic beam into the container, wherein the horizontal component of the axis of the ultrasonic beam is oriented in a direction away from the center of the horizontal shape of the container.

[0015] In one aspect, the horizontal plane shape of the container is a rotationally symmetric shape with the center as the center of rotation.

[0016] In another aspect, the ultrasonic irradiation device has, as the one or more ultrasonic transducers, a plurality of ultrasonic transducers positioned in rotational symmetry with respect to the center.

[0017] In yet another aspect, the ultrasound irradiation device has, as the one or more ultrasound transducers, one or more pairs of ultrasound transducers that irradiate ultrasound beams in directions offset from the center and symmetrical to each other about the center.

[0018] In yet another aspect, the ultrasonic irradiation device further includes an ultrasonic transducer that irradiates an ultrasonic beam vertically upward from the center position of the bottom surface of the container.

[0019] In yet another aspect, the apparatus further includes an ultrasonic transducer that irradiates an ultrasonic beam vertically upward from a position on the bottom surface of the container near the ultrasonic transducer. Effect of the Invention

[0020] According to the present invention, ultrasonic waves can be more uniformly applied to a large number of objects in a liquid in a container. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram for explaining an acoustic physical phenomenon that occurs when an ultrasonic beam is irradiated onto water in a tank from an ultrasonic transducer provided on the side of the tank. [Diagram 2] 1 is a diagram for explaining a force that an object located off the beam axis of an ultrasonic transducer receives from an ultrasonic beam. [Diagram 3] 1 is a diagram showing a schematic view of an ultrasonic irradiation device according to an embodiment as viewed vertically from above; [Figure 4] 1 is a diagram showing a schematic vertical cross section at a certain position of an ultrasonic irradiation device according to an embodiment. FIG. [Diagram 5] FIG. 13 is a diagram showing a schematic view of an ultrasonic irradiation device of Modification 3 as viewed vertically from above. [Figure 6] FIG. 13 is a diagram showing a vertical cross section at a certain position of an ultrasonic irradiation device of Modification 3. [Figure 7] 13 is a diagram for explaining an ultrasonic transducer provided on a downwardly convex bottom surface in Modification 5. FIG. [Figure 8] FIG. 1 is a diagram for explaining the problem of standing waves that can occur when ultrasonic waves are irradiated into a water tank. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <On the problem of standing waves> Before describing a mode for carrying out the present invention (hereinafter referred to as an embodiment), a problem of standing waves that may occur when ultrasonic waves are irradiated into a water tank will be described with reference to FIG.

[0023] Fig. 8 shows a state in which ultrasonic waves are irradiated vertically upward to water 200 in aquarium 100 from ultrasonic transducer 105 provided on the bottom surface of aquarium 100. The water 200 contains a large number of seeds floating in the water. Fig. 1 shows a schematic vertical cross section of aquarium 100 in this state. Here, an example is described in which water 200 is contained in aquarium 100, but the liquid in aquarium 100 may be something other than water.

[0024] Ultrasonic waves 300 emitted from ultrasonic transducer 105 propagate through water 200 from the bottom of water tank 100, and are reflected by water surface 205 to become reflected waves 302 toward the bottom of water tank 100. The reflected waves 302 and ultrasonic waves 300 of traveling waves emitted from ultrasonic transducer 105 (hereinafter also simply referred to as transducer) interfere with each other in the water, forming a sound pressure distribution called a standing wave. On the left side of water tank 100 in FIG. 8, a sound pressure distribution 400 along the depth direction (i.e., Z direction) of water 200 is illustrated. This distribution 400 is on a vertical line passing through the center point of ultrasonic transducer 105. The sound pressure is high at the position of antinode 402 of the standing wave, and low at the position of node 404.

[0025] In a standing wave, unlike a traveling wave, the positions of the antinodes and nodes of this sound pressure do not move but are fixed. If a standing wave occurs where seeds are suspended in water, the seeds move from areas of high sound pressure to areas of low sound pressure and gather. Therefore, the seeds suspended in water have a tendency to move toward node 404.

[0026] Moreover, when observing the direction perpendicular to the beam direction of the ultrasonic beam (called the lateral direction), the sound pressure of the ultrasonic waves is high on the central axis of the ultrasonic beam, i.e., on the central axis (middle) of the transducer, and the sound pressure decreases toward the outside of the transducer (see the sound pressure distribution in the X direction at the bottom of FIG. 8). Due to such a spatial sound pressure distribution, the seeds are repelled by the repulsive force 310 caused by the ultrasonic radiation from the position of high sound pressure to the position of low sound pressure. In other words, the seeds tend to move toward the outside of the ultrasonic beam.

[0027] Therefore, due to these two forces, the seeds suspended in the water form clusters 210 at the height of the standing wave nodes 404, where the sound pressure is low between adjacent transducers. These clusters 210 of seeds remain in the same position.

[0028] In this way, in a situation where the seeds in the water form clusters 210 here and there, it is not possible to quantitatively determine the amount of ultrasound irradiation. Also, the amount of ultrasound irradiation differs between the seeds on the periphery of the cluster and the seeds inside. This hampers accurate experiments and the reproducibility of the germination and growth promotion effects.

[0029] <About acoustic physical phenomena> This embodiment addresses such a problem. Here, referring to FIG. 1, an acoustic physical phenomenon that is the basis of this embodiment will be described. FIG. 1 shows a schematic view of an aquarium 100 filled with water 200, as viewed from above. An ultrasonic beam is emitted from an ultrasonic transducer 110 provided on the left side surface of the aquarium 100 in the figure in the horizontal direction (to the right in the figure) into the water 200 in the aquarium 100. As a result, a traveling wave 320 propagates from the ultrasonic transducer 110 to the right in the water 200. In addition, an ultrasonic radiation force 340 is generated along with this traveling wave 320 due to acoustic nonlinear characteristics. The ultrasonic radiation force 340 also acts on an object 250 (e.g., a seed) in the water, moving the object 250 toward the direction of irradiation of the ultrasonic beam, i.e., toward the right in the figure. At the same time, a water flow called an acoustic stream 330 is also generated due to the acoustic nonlinear characteristics of the water 200. Thus, object 250 moves due to the influence of both radiation force 340 and the surrounding acoustic streaming 330 .

[0030] When the traveling wave 320 is a plane wave, it moves in a direction perpendicular to the transducer surface. However, since the size of the actual transducer surface is finite, the traveling wave 320 emitted from the transducer surface is not a plane wave, and gradually weakens from the center to the outside. For example, in the case of a circular transducer, the sound pressure is strong on the central axis passing through the center of the transducer, and the sound pressure weakens as it approaches the circumference of the transducer from this axis. This is shown by the sound pressure distribution 420 of the ultrasonic beam shown in FIG. 2. When an object 252 is present in a place where there is such a sound pressure gradient, a force (represented by vector B in the figure) that pushes the object 252 from the high sound pressure side to the low sound pressure side acts on the object 252. This force is outward as viewed from the beam axis A1 extending from the center of the transducer surface in the beam direction, that is, a force in a direction away from the axis. Therefore, the object 252 receives a composite force (represented by vector C) of the radiation force (represented by vector A) acting in the direction of the ultrasonic beam and the outward force represented by vector B, and moves in the direction of the composite force.

[0031] <Embodiment> Next, an example of the ultrasonic irradiation device of this embodiment will be described with reference to Fig. 3 and Fig. 4. Fig. 3 shows the ultrasonic irradiation device as viewed vertically from above. Fig. 4 shows the AA cross section (see Fig. 3) of the ultrasonic irradiation device as viewed from the bottom up in the figure.

[0032] This ultrasonic irradiation device includes a water tank 100 and four ultrasonic transducers 110. The water tank 100 is an example of a container for storing liquid. The water tank 100 has a rectangular parallelepiped shape with a square horizontal cross section. The side walls of the water tank 100 have a thickness, but to avoid complexity, the side walls are represented by simple lines in FIG. 1.

[0033] In this example, ultrasonic transducers 110A, 110B, 110C, and 110D (hereinafter collectively referred to as ultrasonic transducer 110 when no distinction is required) are installed on each of the four sides of the water tank 100. The shape of the vibration surface of the ultrasonic transducer 110 is, for example, circular as shown in FIG.

[0034] The position of each ultrasonic transducer 110 in the horizontal plane is offset to one side from the central axis L0, L1 of the side surface of the water tank 100 in the horizontal plane. For example, the central axis L2 of the transducer surface of the ultrasonic transducer 110A (i.e., the axis extending from the center of the transducer surface in the horizontal plane perpendicular to the transducer surface) is offset to the right from the central axis L1 of the side surface extending horizontally in the drawing of the water tank 100. Also, for example, the ultrasonic transducer 110B is provided at a position offset downward from the central axis L0 of the side surface extending vertically in the drawing of the water tank 100. The beam axis of each ultrasonic transducer 110 is offset in the same direction with respect to the central axis L0 or L1 passing through the side surface on which the ultrasonic transducer 110 is provided. In the illustrated example, each ultrasonic transducer 110 is offset to the left side from the corresponding central axis L0 or L1 when viewed in the beam traveling direction. The central axes L0 and L1 of the side surfaces of the aquarium 100 are straight lines perpendicular to the side surfaces of the aquarium 100 and pass through the center O of the square that is the horizontal shape of the aquarium 100.

[0035] In this way, the beam axis of the ultrasonic beam emitted by each ultrasonic transducer 110 is directed in a direction away from the center O of the horizontal shape of the water tank 100.

[0036] In this example, the ultrasonic transducers 110 provided on opposing side surfaces of the aquarium 100 are located in rotational symmetry with the center O of the horizontal shape of the aquarium 100 as the center of rotation. For example, the pair of ultrasonic transducers 110A and 110C provided on opposing side surfaces are located in two-fold rotational symmetry with respect to each other (i.e., they overlap when rotated 180 degrees). Similarly, the pair of ultrasonic transducers 110B and 110D are located in two-fold symmetry with respect to each other. Also, when viewed as a whole, the four ultrasonic transducers 110A, 110B, 110C, and 110D are located in a four-fold symmetric relationship with respect to the center O (i.e., they overlap when rotated 90 degrees).

[0037] In this embodiment, ultrasonic waves are irradiated from the four ultrasonic transducers 110 arranged in this manner toward the inside of the aquarium 100. The ultrasonic transducers 110 irradiate ultrasonic waves from the side toward the water 200 in the aquarium 100. As a result, a rotating flow 350 that rotates clockwise in the figure, with a vertical line passing through the center O as the axis of rotation, can be generated in the water 200 in the aquarium 100, by a mechanism that will be described below.

[0038] That is, ultrasonic waves are emitted from ultrasonic transducers 110 provided on the side surface of the water tank 100 in a direction perpendicular to the transducer surface. For example, ultrasonic transducer 110A emits an ultrasonic beam with the central axis L2 as the beam axis downward in the figure. The directions of the ultrasonic beams emitted by each of the four ultrasonic transducers 110 are also four-fold rotationally symmetric. The irradiation from the four ultrasonic transducers 110 generates traveling waves 320 and acoustic streaming 330 due to ultrasonic radiation force 340, which induce a flow rotating clockwise around the same center O and reinforce each other.

[0039] If the distance between the opposing sides of the water tank 100 (in other words, the length of one side of the square horizontal surface of the water tank 100) is designed to be sufficiently large, the power of the reflected wave when the ultrasonic wave emitted from the ultrasonic transducer 110 provided on one side is reflected by the opposite side will be weak. Therefore, standing waves are unlikely to occur between the opposing sides. Even if a weak standing wave is generated between the opposing sides, the radiation force of the ultrasonic wave is very strong at the location where the acoustic power is strongest, so the forward wave component is very strong, and the water and the object are pushed in the direction of the ultrasonic wave. This creates a rotating flow 350. Taking the ultrasonic transducer 110A as an example, the location where the acoustic power is strongest is a location slightly away from the transducer surface, located between the transducer surface and the central axis L0 of the water tank 100.

[0040] There is no limitation on the type of ultrasonic waves emitted by each ultrasonic transducer 110. For example, the ultrasonic waves may be continuous waves or pulse waves.

[0041] Many small objects such as seeds floating in the water or on the water surface in the water tank 100 are circulated around the water tank 100 on the rotating flow 350 generated by ultrasonic waves from the four ultrasonic transducers 110. The rotating flow 350 allows the objects to be irradiated with ultrasonic waves at various positions without remaining in one place. Therefore, even if one object is viewed as being subjected to ultrasonic irradiation from various directions, the ultrasonic irradiation amount for the many objects becomes nearly uniform overall.

[0042] <Variation 1> In the embodiment shown in FIG. 3 and FIG. 4, four ultrasonic transducers 110 in total are provided, one on each of the four sides of the water tank 100, but this is merely one example.

[0043] The number of ultrasonic transducers 110 provided in the aquarium 100 may be one. In this case, the ultrasonic transducer 110 is provided on one side of the aquarium 100, in a position offset to one side from the center of the side in the horizontal plane. For example, referring to Fig. 3, one example of such a configuration is one in which only ultrasonic transducer 110A is provided in the aquarium 100, and ultrasonic transducers 110B, 110C, and 110D are not provided.

[0044] The number of ultrasonic transducers 110 provided in the water tank 100 may be two. In this case, the two ultrasonic transducers 110 are provided on one side of the water tank 100, each at a position offset from the center of the side in the horizontal plane. The installation positions of the two ultrasonic transducers 110 are rotationally symmetrical with respect to the center O of the horizontal shape of the water tank 100. For example, the two ultrasonic transducers 110 may be provided at positions that are two-fold symmetrical (i.e., point symmetrical) with respect to the center O. Specifically, in the example of FIG. 3, one example is a configuration in which only ultrasonic transducers 110A and 110C are provided in the water tank 100. Even in this configuration, the ultrasonic waves irradiated from the two ultrasonic transducers 110 act to reinforce the rotating flow 350 with each other.

[0045] Furthermore, for example, ultrasonic transducers 110 may be provided on each of two adjacent side surfaces of water tank 100 at positions that overlap when rotated 90 degrees about center O. Specifically, in the example of Fig. 3, one example is a configuration in which only ultrasonic transducers 110A and 110C are provided on water tank 100. In this example, the two ultrasonic transducers 110 also mutually strengthen the rotating flows 350.

[0046] The number of ultrasonic transducers 110 provided in the water tank 100 may be three. In this case, the three ultrasonic transducers 110 are provided on one side of the water tank 100, each at a position offset from the center of the side in the horizontal plane. The installation positions of the three ultrasonic transducers 110 are rotated by 90 degrees from each other with respect to the center O of the horizontal shape of the water tank 100. Specifically, in the example of FIG. 3, one example is a configuration in which only ultrasonic transducers 110A, 110B, and 110C are provided in the water tank 100. In this example, the three ultrasonic transducers 110 act to mutually strengthen the rotating flows 350.

[0047] <Variation 2> In the example of Figs. 3 and 4, the horizontal plane shape of the water tank 100 is a square, but this is merely one example.

[0048] The horizontal shape of the aquarium 100 may be a regular polygon having pentagons or more. The horizontal shape of the aquarium 100 is not limited to a regular polygon, and may be, for example, a shape that is rotationally symmetric with respect to the center of the horizontal shape. In the case of a regular polygon or a more general rotationally symmetric shape, the ultrasonic transducer 110 is provided on one or more side surfaces of the horizontal shape. The ultrasonic transducer 110 is disposed on the side surface of the aquarium 100 at a position and orientation determined so that the beam axis of the irradiated ultrasonic waves does not pass through the center of the horizontal shape of the aquarium 100. Since the beam axis does not pass through the center, the flow of water generated by the ultrasonic waves irradiated by the ultrasonic transducer 110 generates a rotational flow around the center. When multiple ultrasonic transducers 110 are provided in the aquarium 100, it is desirable to determine the position and orientation of each ultrasonic transducer 110 so that the flows generated by each of the multiple ultrasonic transducers 110 generate rotational flows in the same direction.

[0049] <Modification 3> Objects such as seeds in a rotating flow generated by ultrasonic waves have the characteristic of gathering in places where the flow speed is slow. For this reason, in the example of Fig. 3, a phenomenon occurs in which objects gather near the center O of the horizontal shape of the aquarium 100. Also, the radiation force of the ultrasonic waves is strong at a position a little farther away from the ultrasonic transducer 110, but is weak at a position very close to the ultrasonic transducer 110. For this reason, objects that are very close to the ultrasonic transducer 110 are slowly carried by the water flow and move to the four corners of the horizontal shape of the aquarium 100. Since the flow speed is slow at the four corners, objects tend to gather and stagnate there.

[0050] Since the center O and the four corners of the water tank 100 are far from the ultrasonic beam from the ultrasonic transducers 110, the ultrasonic waves received by objects at those positions are much weaker than the ultrasonic waves received by objects circulating on the rotating flow near the beam axis of each ultrasonic transducer 110. Therefore, objects gathered at the center O and the four corners of the water tank 100 may not achieve the expected effect of ultrasonic irradiation. Modification 3 addresses this problem.

[0051] Fig. 5 shows a schematic diagram of the ultrasonic irradiation device of the third modified example. Fig. 5 shows a schematic diagram of the ultrasonic irradiation device as viewed vertically from above. Fig. 6 shows a schematic diagram of the AA cross section (see Fig. 6) of the ultrasonic irradiation device as viewed from bottom to top in the figure. In Fig. 5 and Fig. 6, the same reference numerals as in Fig. 3 are used for components having the same roles as those of the components of the device in Fig. 3.

[0052] The horizontal shape of the water tank 100 of this ultrasonic irradiation device is an octagon with the four corners of a square cut at a shallow angle, and has a four-fold symmetric shape. Ultrasonic transducers 110 are provided on the side of the cut lines of the four corners of the water tank 100. The beam axes of the four ultrasonic transducers 110 are oriented in a direction shifted from the center O of the horizontal shape of the water tank 100, and are in a four-fold symmetric relationship. The radiation force of the ultrasonic waves emitted by the four ultrasonic transducers 110 on the side of the water tank 100 (the direction is indicated by the arrow S in the figure) generates a clockwise rotating flow in the water 200 in the water tank 100, as in the above embodiment shown in FIG. 3.

[0053] In this modification, ultrasonic transducers 120 and 130A-D are provided on the bottom surface of aquarium 100. Of these, ultrasonic transducer 120 is provided at the center O of the bottom surface. Ultrasonic transducer 120 irradiates an ultrasonic beam vertically upward from the center O of the bottom surface. The remaining four ultrasonic transducers 130A-D (hereinafter collectively referred to as ultrasonic transducer 130 unless distinction is required) are provided on the bottom surface of aquarium 100 in close proximity to ultrasonic transducer 110 on the side surface of aquarium 100.

[0054] The locations where these five ultrasonic transducers 120 and 130 are provided are locations where objects are likely to remain because the flow velocity of the rotating flow generated by the four ultrasonic transducers 110 on the sides is slow, and where the ultrasonic waves irradiated by these ultrasonic transducers 110 are quite weak.

[0055] One of the roles of the ultrasonic transducers 120 and 130 is to irradiate ultrasonic waves to the object at those positions. Since the ultrasonic waves received by the object at those positions from the ultrasonic transducer 110 on the side are quite weak, the ultrasonic waves from the ultrasonic transducers 120 and 130 supplement the weak ultrasonic waves.

[0056] An additional role of the ultrasonic transducers 120 and 130 is to push objects at their location into the rotating flow.

[0057] Specifically, first, objects gathered near the center O of the horizontal shape of the water tank 100 (shown as a group of objects G1 in the figure) are pushed in the direction of the rotating flow around the center O by ultrasonic irradiation from the ultrasonic transducer 120 located directly below them. That is, since the ultrasonic beam from the ultrasonic transducer 120 is strongest on the beam axis and becomes weaker the further away from the beam axis, a force F1 in a direction away from the beam axis, i.e., the vertical axis passing through the center O, is applied to each object according to the ultrasonic intensity profile.

[0058] Also, for example, the area of ​​the near-field sound field of the ultrasonic transducer 110C on the side (i.e., the location of the assembly G2 directly above the ultrasonic transducer 110C in the figure) has a weaker ultrasonic radiation force than the area from the ultrasonic transducer 110, so objects tend to accumulate there. The ultrasonic transducer 130C provided on the bottom surface acts to push the assembly G2 of objects accumulated in that area in the direction of the rotating flow. That is, the force due to the profile of the upward ultrasonic beam from the ultrasonic transducer 130C on the bottom surface is combined with the ultrasonic radiation force from the ultrasonic transducer 110C on the side surface, and the resultant force F2 moves the objects in the assembly G2 in the direction of the rotating flow closer to the center O.

[0059] Also, at the position of assembly G3, the objects in assembly G3 are pushed closer to the center O and carried by the rotating flow due to a resultant force F3 of the ultrasonic waves from ultrasonic transducer 110D on the side and ultrasonic transducer 130D on the bottom, and the radiation force of the ultrasonic waves reflected by the slanted side wall (the wall between ultrasonic transducer 110D and ultrasonic transducer 110C) in front of the traveling wave of ultrasonic transducer 110C (not shown).

[0060] In this way, in the third modification, due to the combined action of the ultrasonic waves from the ultrasonic transducer 110 on the side and the ultrasonic transducer 120 or 130 on the bottom, the objects in the tank 100 are less likely to remain in one place, and are circulated within the tank 100 by riding on the rotating current around the center O. These circulating objects are then irradiated with ultrasonic waves from various directions by the ultrasonic transducers 110, 120, and 130. This allows a large number of objects, such as seeds, to be irradiated with nearly equal amounts of ultrasonic waves.

[0061] <Modification 4> In the above embodiment and each modified example, the ultrasonic transducer 110 that generates a rotating flow is provided on a side surface perpendicular to the bottom surface of the water tank 100, and the beam axis is oriented in a horizontal plane. However, although a rotating flow is generated by using the ultrasonic transducer 110 oriented in this way, it is not essential to have the transducer oriented in this way.

[0062] To generate a rotating flow, the beam axis of the ultrasonic beam emitted from the ultrasonic transducer 110 needs to have a horizontal component. If the direction of this horizontal component is different from the direction toward the center O of the horizontal shape of the water tank 100, as in the example of FIG. 3, etc., a rotating flow is induced by the horizontal component.

[0063] Therefore, for example, the side of the water tank 100 may be inclined rather than perpendicular to the bottom surface, and the ultrasonic transducer 110 may be provided on the inclined side. Since the beam axis of the ultrasonic transducer 110 provided on the inclined side has a horizontal component, the horizontal component of the radiation force of the emitted ultrasonic waves induces a rotational flow around the center O. For example, if the horizontal cross section is a square and the four side surfaces are inclined outward toward the top, four ultrasonic transducers 110 may be provided on the four side surfaces so that their positional relationship in the horizontal plane is the same as that in FIG. 3. In this case, the horizontal components of the ultrasonic waves emitted from the four ultrasonic transducers 110 act to reinforce the same clockwise rotating flows.

[0064] <Variation 5> In the above-mentioned modification 4, the side of the water tank 100 is inclined. In contrast, in this modification 5, the bottom surface of the water tank 100 is a curved surface or a polyhedron convex downward. Then, the ultrasonic transducer 120 is provided along this bottom surface. FIG. 7 shows a schematic cross section when the bottom surface 105 of the water tank 100 is a curved surface convex downward. In the modification 4 (see FIG. 6), the beam axis of the ultrasonic transducer 120 provided on the flat bottom surface was oriented vertically, but in this modification 5, the beam axis 125 of the ultrasonic transducer 105 provided on the convex bottom surface 105 is inclined toward the inside of the water tank 100. That is, the beam axis 125 is inclined so as to face toward the side closer to the vertical line passing through the center O of the horizontal surface shape of the water tank 100 rather than in the vertical upward direction. In this case, the beam axis 125 may be oriented toward a point on the vertical line, but this is not necessarily the case. By tilting the ultrasonic transducer 120 on the bottom surface 105 inward in this manner, objects that tend to gather in the corners of the aquarium 100 can be moved toward the inside of the aquarium 100 and easily entrained in the rotating flow, more so than in the examples shown in Figures 5 and 6.

[0065] The above-described embodiment and modifications are merely illustrative, and various modifications and improvements are possible within the scope of the technical idea of ​​the present invention as set forth in the claims. [Explanation of symbols]

[0066] 100 water tank, 105, 110, 110A, 110B, 110C, 110D, 120, 130, 130A, 130B, 130C, 130D ultrasonic vibrators, 200 water, 320 progressive wave, 330 acoustic streaming, 340 radiation force.

Claims

1. A container for containing a liquid containing an object to be irradiated with ultrasound; One or more ultrasonic transducers that irradiate an ultrasonic beam into the container, the one or more ultrasonic transducers having a horizontal component of an axis of the ultrasonic beam that is oriented in a direction away from the center of the horizontal plane shape of the container; An ultrasonic irradiation device having the above structure.

2. 2. The ultrasonic irradiation device according to claim 1, wherein the horizontal plane shape of the container is a rotationally symmetric shape with the center as a center of rotation.

3. 2. The ultrasonic irradiation device according to claim 1, wherein the one or more ultrasonic transducers include a plurality of ultrasonic transducers positioned in rotational symmetry with respect to the center.

4. The one or more ultrasonic transducers include 2. The ultrasonic irradiation device according to claim 1, further comprising one or more pairs of ultrasonic transducers that irradiate ultrasonic beams in directions offset from the center and symmetrical with respect to each other about the center.

5. The ultrasonic irradiation device according to claim 1 , further comprising an ultrasonic transducer that irradiates an ultrasonic beam vertically upward from the center position of the bottom surface of the container.

6. The ultrasonic irradiation device according to claim 1 , further comprising an ultrasonic transducer that irradiates an ultrasonic beam vertically upward from a position on the bottom surface of the container near the ultrasonic transducer.

7. The ultrasonic irradiation device according to claim 1 , further comprising an ultrasonic transducer that irradiates an ultrasonic beam in a direction inclined toward the inside of the container from a position on the bottom surface of the container near the ultrasonic transducer.

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