[Technical Field]
5 [0001]
The present invention relates to an ultrasonic treatment apparatus, and a fine
bubble supply method.
[Background Art]
[0002]
10 Generally, in a manufacturing process of various types of metal objects such as
steel plates and steel pipes, a cleaning treatment method is widely used to remove dirt,
scales, and the like on a surface of the metal object by immersing it in a cleaning tank that
contains chemical solutions, rinses, and so on. Examples of cleaning treatment
apparatuses performing such cleaning treatment methods include, for example, a treatment
15 apparatus using high-pressure airflow injection nozzles and an ultrasonic treatment
apparatus using ultrasonic waves.
[0003]
In the ultrasonic treatment apparatus using ultrasonic waves as above, in order to
strengthen a cavitation action in the ultrasonic cleaning, a measure is taken such that
20 deaeration is performed for improving ultrasonic propagation property, and micro bubbles
to be a core of cavitation are introduced. For example, as a method of performing the
deaeration, a deaeration method using a vacuum pump, a deaeration method using a hollow
fiber membrane, a deaeration method using throttling, and the like are proposed. Further,
for example, as methods of introducing micro bubbles, a bubble micronizing method
25 through high-speed spiral flow, a method in which gas is dissolved in a supersaturated state
under high pressure, and micro bubbles are generated during release, and so on are
2
proposed. However, each of the deaeration methods and the micro bubble generating
methods as described above requires a dedicated unit, and an apparatus that performs these
methods in combination is large in size and very expensive.
[0004]
5 Accordingly, in recent years, studies are being conducted regarding an apparatus
in which stable generation of micro bubbles and regulation of dissolved gas amount
(namely, deaeration) are integrally performed.
[0005]
For example, the following Patent Document 1 proposes an apparatus in which
10 bubbles are generated by an obstacle provided in a flow path for introducing a cleaning
liquid into a propeller-type circulating pump, the bubbles are micronized by the propeller
of the circulating pump, and deaeration of the cleaning liquid is performed by a deaeration
device connected to the flow path.
[0006]
15 Further, the following Patent Document 2 proposes a method in which liquid is
introduced into a suction pipe line of a liquid feed pump, and a part of the suction pipe line
is throttled, to thereby reduce a pressure between the throttle and the liquid feed pump and
let dissolved gas in the liquid free as bubbles.
[0007]
20 Further, the following Patent Document 3 proposes an apparatus in which, with
respect to a circulation path for circulating a treatment liquid, two pumps are provided so
that their liquid feeding directions become opposite to each other, to thereby perform
deaeration of the treatment liquid and generation of micro bubbles.
[0008]
25 Further, as a technique for generating micro bubbles, each of the following Patent
Document 4 and Patent Document 5 proposes a method in which baffle plates and the like
3
are provided with an interval therebetween in a flow path of liquid, and cavitation caused
when the liquid collides with the baffle plates and the like, is utilized.
[Prior Art Document]
[Patent Document]
5 [0009]
Patent Document 1: Japanese Laid-open Patent Publication No. 2008-296217
Patent Document 2: Japanese Laid-open Patent Publication No. H7-328316
Patent Document 3: Japanese Laid-open Patent Publication No. 2020-14989
Patent Document 4: Japanese Laid-open Patent Publication No. 2005-95877
10 Patent Document 5: Japanese Translation of PCT International Application
Publication No. JP-T-2016-536139
[Disclosure of the Invention]
[Problems to Be Solved by the Invention]
[0010]
15 However, in the technique disclosed in the above Patent Document 1 and Patent
Document 2, although micro bubbles can be generated, fine bubbles having a bubble
diameter that sufficiently complies with a cleaning treatment using ultrasonic waves, are
not generated in a stable manner. Further, in the technique disclosed in the above Patent
Document 1, the micro bubbles are generated by shearing the bubbles using the propeller
20 of the circulating pump, and thus the propeller may be damaged by erosion-corrosion, and
durability of the apparatus is not sufficient. Besides, in the technique disclosed in the
above Patent Document 2, there is provided a gas-liquid separation tank for making the
generated bubbles to be floated and separated, in which coarse bubbles are intentionally
generated for the purpose of eliminating the bubbles, and thus there is no ability of
25 generating fine bubbles.
[0011]
4
Further, even if the techniques disclosed in the above Patent Document 3 to Patent
Document 5 are used, there is still room for improvement in view of the stable generation
of fine bubbles having a bubble diameter that sufficiently complies with a cleaning
treatment using ultrasonic waves.
5 [0012]
In particular, the above Patent Document 4 describes the technique in which
pressure reduction is performed from a pressurized state, to thereby micronize bubbles
generated by cavitation. As a result of studies conducted by the present inventors, it has
been clarified that gas dissolved in liquid cannot be turned into bubbles unless a pressure
10 after the pressure reduction can be set to 1 atmosphere or less. For this reason, in the
above Patent Document 4, it becomes difficult to realize both the deaeration and the
generation of fine bubbles.
[0013]
The present invention was made in view of the above problems, and an object
15 thereof is to provide an ultrasonic treatment apparatus excellent in durability of the
apparatus, capable of realizing a dissolved gas amount suitable for propagation of
ultrasonic waves, and stably generating fine bubbles that further comply with a treatment
using ultrasonic waves, and a fine bubble supply method.
[Means for Solving the Problems]
20 [0014]
As a result of earnest studies conducted by the present inventors to solve the
above problems, it is possible to obtain findings that, by properly providing a plurality of
stages of narrow portions satisfying predetermined conditions to a pipe that introduces a
treatment liquid into a circulating pump, it is possible to stably generate fine bubbles that
25 further comply with a treatment using ultrasonic waves, and no influence is exerted also on
durability of a mechanism, which led to completion of the present invention.
5
The gist of the present invention completed based on the above findings is as
follows.
[0015]
[1] An ultrasonic treatment apparatus includes: a treatment part capable of accommodating
5 a treatment liquid and an object to be treated; an ultrasonic generator that is provided in the
treatment part and applies ultrasonic waves to the object to be treated; and a circulation
path for circulating the treatment liquid in the treatment part, in which the circulation path
has a circulating pump for circulating the treatment liquid, a treatment liquid extraction
pipe that connects the treatment liquid extracted from the treatment part to the circulating
10 pump, and a treatment liquid discharge pipe that discharges the treatment liquid passed
through the circulating pump to the treatment part, and a fine bubble generator which
performs deaeration on the extracted treatment liquid and generates fine bubbles in the
treatment liquid, is provided to the circulation path, in series with the treatment liquid
extraction pipe, in which the fine bubble generator has two or more narrow portions each
15 having an opening flow path of the treatment liquid with a size narrower than an inside
diameter of the treatment liquid extraction pipe, in which the opening flow paths of the
narrow portions adjacent to each other are configured to prevent the treatment liquid from
proceeding straight, in which regarding each of the narrow portions, when an opening
cross-sectional area of the inside diameter of the treatment liquid extraction pipe is set to
20 A0, and an opening cross-sectional area of the inside diameter of the treatment liquid
extraction pipe at an i (i is an integer of 1 or more)-th narrow portion from the treatment
part side toward the circulating pump side is represented as Ai, an opening cross-sectional
area ratio Ri of the i-th narrow portion represented as Ai/A0 satisfies the following formula
(1), and when an interval between the i-th narrow portion and an i+1-th narrow portion is
25 represented as Li, the following formula (2) is satisfied.
[2] In the ultrasonic treatment apparatus described in [1], when the treatment liquid
6
extraction pipe is seen from a pipe axis direction, positions of the opening flow paths of the
narrow portions adjacent to each other are not overlapped with each other.
[3] In the ultrasonic treatment apparatus described in [1] or [2], a treatment tank which
contains the treatment liquid is provided as the treatment part, and the ultrasonic generator
5 indirectly applies ultrasonic waves to the object to be treated via the treatment liquid.
[4] In the ultrasonic treatment apparatus described in [1] or [2], the ultrasonic generator
directly applies ultrasonic waves to the object to be treated that is immersed in the
treatment liquid in the treatment part.
[5] In the ultrasonic treatment apparatus described in any one of [1] to [4], when the
10 number of the narrow portions is set to N, and an N-th opening area ratio from the
treatment part side toward the circulating pump side is represented as RN, the following
formula (3) and formula (4) are satisfied.
[6] In the ultrasonic treatment apparatus described in any one of [1] to [5], the number N of
the narrow portions is 2 to 10.
15 [7] The ultrasonic treatment apparatus described in any one of [1] to [6] has one or a
plurality of the narrow portions each formed by a projecting member projecting from an
inner surface of the treatment liquid extraction pipe.
[8] The ultrasonic treatment apparatus described in [7] has, as the narrow portion, a
movable projecting member projecting from the inner surface of the treatment liquid
20 extraction pipe.
[9] The ultrasonic treatment apparatus described in any one of [1] to [8] has one or a
plurality of the narrow portions each formed by an opening member provided with one or a
plurality of through holes.
[10] In the ultrasonic treatment apparatus described in any one of [1] to [9], the ultrasonic
25 generator can select a frequency of the ultrasonic waves from a frequency band of 20 kHz
to 200 kHz.
7
[11] In the ultrasonic treatment apparatus described in any one of [1] to [10], the ultrasonic
generator can apply ultrasonic waves to the treatment liquid while performing a sweep
within a range of ±0.1 kHz to ±10 kHz centered on a selected frequency of the ultrasonic
waves.
5 [12] A fine bubble supply method of supplying, when performing a predetermined
treatment on an object to be treated while applying ultrasonic waves to a treatment part
capable of accommodating a treatment liquid and the object to be treated, the treatment
liquid containing fine bubbles to the treatment part, in which an ultrasonic generator that is
provided in the treatment part and applies ultrasonic waves to the object to be treated, and
10 a circulation path for circulating the treatment liquid in the treatment part are provided with
respect to the treatment part, in which the circulation path has a circulating pump for
circulating the treatment liquid, a treatment liquid extraction pipe that connects the
treatment liquid extracted from the treatment part to the circulating pump, and a treatment
liquid discharge pipe that discharges the treatment liquid passed through the circulating
15 pump to the treatment part, and a fine bubble generator which performs deaeration on the
extracted treatment liquid and generates fine bubbles in the treatment liquid, is provided to
the circulation path, in series with the treatment liquid extraction pipe, in which the fine
bubble generator has two or more narrow portions each having an opening flow path of the
treatment liquid with a size narrower than an inside diameter of the treatment liquid
20 extraction pipe, in which the opening flow paths of the narrow portions adjacent to each
other are configured to prevent the treatment liquid from proceeding straight, in which
regarding each of the narrow portions, when an opening cross-sectional area of the inside
diameter of the treatment liquid extraction pipe is set to A0, and an opening cross-sectional
area of the inside diameter of the treatment liquid extraction pipe at an i (i is an integer of 1
25 or more)-th narrow portion from the treatment part side toward the circulating pump side is
represented as Ai, an opening cross-sectional area ratio Ri of the i-th narrow portion
8
represented as Ai/A0 satisfies the following formula (1), and when an interval between the
i-th narrow portion and an i+1-th narrow portion is represented as Li, the following formula
(2) is satisfied.
[13] In the fine bubble supply method described in [12], the fine bubble generator
5 generates the fine bubbles to make a dissolved gas amount to be 50% or less of a saturated
dissolved gas amount in the treatment liquid to be discharged to the treatment part.
[14] In the fine bubble supply method described in [12] or [13], the fine bubble generator
generates the fine bubbles to make the fine bubbles having an average bubble diameter of 1
μm to 100 μm exist at a bubble number density in a range of 1 × 103 pieces/mL to 1 × 1010
10 pieces/mL in the treatment liquid to be discharged to the treatment part.
[15] In the fine bubble supply method described in any one of [12] to [14], the ultrasonic
generator selects a frequency of the ultrasonic waves from a frequency band of 20 kHz to
200 kHz.
[16] In the fine bubble supply method described in any one of [12] to [15], the ultrasonic
15 generator applies ultrasonic waves to the treatment liquid while performing a sweep within
a range of ±0.1 kHz to ±10 kHz centered on a selected frequency of the ultrasonic waves.
[0016]
Ri = 0.10 to 0.50 ··· Formula (1)
1.0 ≤ Li/2(A0/π)0.5 ≤ 5.0 ··· Formula (2)
20 Ri+1 ≥ Ri ··· Formula (3)
RN/R1 ≥ 1.10 ··· Formula (4)
[Effect of the Invention]
[0017]
As described above, according to the present invention, it is possible to provide an
25 ultrasonic treatment apparatus capable of realizing a dissolved gas amount suitable for
propagation of ultrasonic waves, stably generating fine bubbles that further comply with a
9
treatment using ultrasonic waves, and being excellent in durability of the apparatus, and a
fine bubble supply method.
[Brief Description of the Drawings]
[0018]
5 [FIG. 1A] FIG. 1A is an explanatory diagram schematically illustrating an
example of a configuration of an ultrasonic treatment apparatus according to an
embodiment of the present invention.
[FIG. 1B] FIG. 1B is an explanatory diagram schematically illustrating an
example of a configuration of an ultrasonic treatment apparatus according to the
10 embodiment.
[FIG. 2] FIG. 2 is an explanatory diagram for explaining a fine bubble generator
provided to the ultrasonic treatment apparatus according to the embodiment.
[FIG. 3] FIG. 3 is an explanatory diagram for explaining a fine bubble generator
provided to the ultrasonic treatment apparatus according to the embodiment.
15 [FIG. 4] FIG. 4 is an explanatory diagram for explaining a fine bubble generator
provided to the ultrasonic treatment apparatus according to the embodiment.
[FIG. 5] FIG. 5 is an explanatory diagram for explaining a fine bubble generator
provided to the ultrasonic treatment apparatus according to the embodiment.
[FIG. 6] FIG. 6 is an explanatory diagram for explaining a fine bubble generator
20 provided to the ultrasonic treatment apparatus according to the embodiment.
[FIG. 7] FIG. 7 is an explanatory diagram for explaining a fine bubble generator
provided to the ultrasonic treatment apparatus according to the embodiment.
[FIG. 8] FIG. 8 is an explanatory diagram for explaining a fine bubble generator
provided to the ultrasonic treatment apparatus according to the embodiment.
25 [FIG. 9A] FIG. 9A is a graph diagram illustrating a state of pressure change inside
the fine bubble generator.
10
[FIG. 9B] FIG. 9B is a graph diagram illustrating a state of pressure change inside
the fine bubble generator.
[FIG. 9C] FIG. 9C is a graph diagram illustrating a state of pressure change inside
the fine bubble generator.
5 [FIG. 9D] FIG. 9D is a graph diagram illustrating a state of pressure change inside
the fine bubble generator.
[FIG. 9E] FIG. 9E is a graph diagram illustrating a state of pressure change inside
the fine bubble generator.
[FIG. 10A] FIG. 10A is a graph diagram illustrating a state of pressure distribution
10 inside the fine bubble generator.
[FIG. 10B] FIG. 10B is a graph diagram illustrating a state of pressure distribution
inside the fine bubble generator.
[FIG. 10C] FIG. 10C is a graph diagram illustrating a state of pressure distribution
inside the fine bubble generator.
15 [FIG. 10D] FIG. 10D is a graph diagram illustrating a state of pressure
distribution inside the fine bubble generator.
[FIG. 11] FIG. 11 is a graph diagram for explaining the fine bubble generators.
[FIG. 12] FIG. 12 is a graph diagram for explaining the fine bubble generator.
[FIG. 13] FIG. 13 is a graph diagram for explaining the fine bubble generator.
20 [FIG. 14] FIG. 14 is a graph diagram illustrating a relation between a fine bubble
particle diameter and a dissolved oxygen concentration.
[FIG. 15] FIG. 15 is an explanatory diagram schematically illustrating a
configuration of an apparatus used in an experimental example 1.
[FIG. 16] FIG. 16 is an explanatory diagram schematically illustrating
25 configurations of fine bubble generators used in the experimental example 1.
[FIG. 17A] FIG. 17A is an explanatory diagram schematically illustrating a
11
configuration of an ultrasonic treatment apparatus used in an experimental example 2.
[FIG. 17B] FIG. 17B is an explanatory diagram schematically illustrating a
configuration of the ultrasonic treatment apparatus used in the experimental example 2.
[FIG. 18] FIG. 18 is an explanatory diagram for explaining measurement positions
5 of ultrasonic intensities.
[FIG. 19A] FIG. 19A is an explanatory diagram schematically illustrating a
configuration of an ultrasonic treatment apparatus used in an experimental example 3.
[FIG. 19B] FIG. 19B is an explanatory diagram schematically illustrating a
configuration of the ultrasonic treatment apparatus used in the experimental example 3.
10 [FIG. 20] FIG. 20 is an explanatory diagram schematically illustrating a
configuration of an ultrasonic treatment apparatus used in an experimental example 4.
[Embodiments for Carrying out the Invention]
[0019]
Hereinafter, preferred embodiments of the present invention will be described in
15 detail with reference to the attached drawings. In the Description and the drawings,
components having substantially the same functional configurations are denoted by the
same codes, to thereby omit overlapped explanation.
[0020]
(Overall configuration of ultrasonic treatment apparatus)
20 First, an overall configuration of an ultrasonic treatment apparatus according to an
embodiment of the present invention will be briefly described while referring to FIG. 1A
and FIG. 1B. FIG. 1A and FIG. 1B are explanatory diagrams each schematically
illustrating an example of the overall configuration of the ultrasonic treatment apparatus
according to the present embodiment.
25 [0021]
An ultrasonic treatment apparatus 1 according to the present embodiment is an
12
apparatus that performs a predetermined treatment on a surface of an object to be treated (a
portion in contact with a treatment liquid) by using not only the treatment liquid for
performing the predetermined treatment on the object to be treated but also ultrasonic
waves. The ultrasonic treatment apparatus 1 can be used when various types of
5 treatments such as cleaning, for example, are applied to various types of metal objects
represented by steel materials, various types of non-metal objects represented by plastic
resin members, and so on. For example, various types of metal objects such as steel
plates, steel pipes, and steel wire materials are set to the objects to be treated, and by using
the ultrasonic treatment apparatus 1 according to the present embodiment, it is possible to
10 perform a pickling treatment, a degreasing treatment, and a cleaning treatment on these
metal objects. Further, the ultrasonic treatment apparatus 1 according to the present
embodiment can be used also when performing a water washing treatment after the
pickling treatment.
[0022]
15 Here, the pickling treatment is a treatment for removing oxide scales formed on a
surface of the metal object by using an acid solution, and the degreasing treatment is a
treatment for removing oil such as lubricant or machining oil used in processing or the like,
by using an organic solvent, an organic solvent emulsified with a surface active agent, or
an alkali-based degreasing liquid. These pickling treatment and degreasing treatment are
20 pretreatments performed before applying surface finishing treatments (metal coating
treatment, conversion treatment, paint treatment, and so on) to metal objects. The
pickling treatment may dissolve a part of base metal. The pickling treatment is also used
to dissolve metal objects by etching to improve surface finishing quality. In some cases,
the degreasing treatment is provided before the pickling treatment, and degreasing
25 performance in the degreasing treatment may affect the scale removal in the subsequent
pickling treatment. Furthermore, the degreasing treatment is also used to improve
13
wettability, which is an index of oil content control as a finishing quality of a final product.
[0023]
Furthermore, the ultrasonic treatment apparatus 1 according to the present
embodiment to be described in detail below, can also be used for cleaning used pipes, tanks
5 and apparatuses that require dirt removal on regular or irregular basis, or the like in
addition to the cleaning process in a manufacturing line as described above.
[0024]
Hereinafter, a detailed explanation will be made by citing a case, as an example, in
which a treatment tank that contains a treatment liquid exists as an example of a treatment
10 part, and an object to be treated is provided so as to be filled with the treatment liquid in
the treatment tank.
[0025]
However, the ultrasonic treatment apparatus 1 according to the present
embodiment can be employed without separately providing the treatment tank when a
15 member which is previously provided to an apparatus to be a treatment target can be used
as a treatment tank, as in a case where an ultrasonic treatment is performed on a pipe
provided to a heat exchanger, for example.
[0026]
As exemplified in FIG. 1A, the ultrasonic treatment apparatus 1 according to the
20 present embodiment has a treatment tank 10, an ultrasonic generator 20, and a treatment
liquid circulation path 30. Further, as illustrated in FIG. 1A, the treatment liquid
circulation path 30 has a circulating pump 31, a treatment liquid extraction pipe 33, and a
treatment liquid discharge pipe 35, and a fine bubble generator 40 is provided in series
with the treatment liquid extraction pipe 33. By the fine bubble generator 40, fine
25 bubbles are generated in a treatment liquid 3 that flows through the circulation path 30, and
the generated fine bubbles are supplied into the treatment tank 10 together with the
14
treatment liquid 3. Further, the ultrasonic treatment apparatus 1 according to the present
embodiment preferably has a curved member 50, in addition to the above configuration.
[0027]
Here, the fine bubbles are micro bubbles having a bubble diameter of 100 μm or
5 less. The fine bubbles improve a propagation efficiency of ultrasonic waves with respect
to an object to be treated, to thereby improve a treatment performance as a core of
ultrasonic cavitation.
[0028]
Further, as schematically illustrated in FIG. 1B, the number and the arrangement
10 of the ultrasonic generator 20, the circulation path 30, the fine bubble generator 40, and the
curved member 50 are not particularly limited, and it is possible to arrange these while
adjusting the number thereof appropriately, in accordance with a shape and a size of the
treatment tank 10. Note that a size of each member in the drawing is emphasized
appropriately for simplifying the explanation, and thus actual dimension and ratio between
15 members are not illustrated.
[0029]
Hereinafter, respective configurations in the ultrasonic treatment apparatus 1
according to the present embodiment will be described in detail.
[0030]
20
In the treatment tank 10 being an example of a treatment part, the treatment liquid
3 used for performing a predetermined treatment on an object to be treated, and the object
to be treated itself are accommodated. Accordingly, when the object to be treated
accommodated in the treatment tank 10 is immersed in the treatment liquid 3, it exists in a
25 state of being filled with the treatment liquid 3. Types of the treatment liquid 3 contained
in the treatment tank 10 are not limited in particular, and it is possible to use a
15
publicly-known treatment liquid according to a treatment to be performed on the object to
be treated.
[0031]
Here, a material used for forming the treatment tank 10 according to the present
5 embodiment is not limited in particular, and it may be various types of metal materials
such as iron, steel, and stainless steel plates, various types of plastic resins such as fiber
reinforced plastic (FRP) and polypropylene (PP), or various types of bricks such as an
acid-resistant brick. Specifically, as the treatment tank 10 composing the ultrasonic
treatment apparatus 1 according to the present embodiment, it is possible to newly prepare
10 a treatment tank formed of the material as described above, and it is also possible to use an
existing treatment tank in various types of manufacturing lines.
[0032]
Further, a size of the treatment tank 10 is also not limited in particular, and even a
large-sized treatment tank of various shapes such as one with a liquid level depth of about
15 1 to 2 m and an entire length of about 3 to 25 m, can also be used as the treatment tank 10
of the ultrasonic treatment apparatus 1 according to the present embodiment.
[0033]

The ultrasonic generator 20 applies ultrasonic waves at a predetermined frequency
20 to the treatment liquid 3 and the object to be treated accommodated in the treatment tank
10. The ultrasonic generator 20 is not limited in particular, and it is possible to use a
publicly-known one such as an ultrasonic transducer connected to a not-illustrated
ultrasonic oscillator. Furter, although each of FIG. 1A and FIG. 1B illustrates a case
where the ultrasonic generator 20 is provided to a wall surface of the treatment tank 10, a
25 position of installing the ultrasonic generator 20 to the treatment tank 10 is also not limited
in particular, and it is only required to appropriately install one or a plurality of ultrasonic
16
transducers to the wall surface or a bottom surface of the treatment tank 10. Note that
when employing a condition in which ultrasonic waves uniformly propagate in the entire
treatment tank 10, balances of oscillation loads of individual ultrasonic transducers become
uniform, and thus even if the plurality of ultrasonic transducers are provided, no
5 interference occurs among the generated ultrasonic waves.
[0034]
A frequency of ultrasonic waves output from the ultrasonic generator 20 is
preferably 20 kHz to 200 kHz, for example. When the frequency of ultrasonic waves is
less than 20 kHz, ultrasonic propagation may be inhibited by large-sized bubbles generated
10 from a surface of the object to be treated, which may reduce the effect of improving
treatment performance provided by ultrasonic waves. Further, when the frequency of
ultrasonic waves exceeds 200 kHz, a straight proceeding property of ultrasonic waves
when treating the object to be treated becomes excessively strong, and the uniformity of
treatment may be lowered. The frequency of ultrasonic waves output from the ultrasonic
15 generator 20 is more preferably 20 kHz to 150 kHz, and still more preferably 25 kHz to
100 kHz.
[0035]
Note that the frequency of ultrasonic waves to be applied is preferably selected to
an appropriate value within the above range according to the object to be treated, and
20 depending on the type of the object to be treated, ultrasonic waves at two or more
frequencies may be applied.
[0036]
Further, the ultrasonic generator 20 preferably has a frequency sweep function,
which is capable of applying ultrasonic waves while sweeping the frequency within a
25 predetermined range centered on a certain selected frequency of ultrasonic waves. Such a
frequency sweep function enables to achieve the following two additional effects.
17
[0037]
When ultrasonic waves are applied to micro bubbles including fine bubbles that
exist in a liquid, force called Bjerknes force acts on the micro bubbles, and the micro
bubbles are pulled to positions of a point of peak or inflection of ultrasonic waves in
5 accordance with a resonant bubble radius R0 that depends on a frequency. Here, when the
frequency of ultrasonic waves changes due to the frequency sweep function possessed by
the ultrasonic generator 20, the resonant bubble radius R0 that depends on a frequency
varies according to the change in the frequency. Consequently, a bubble diameter when
causing cavitation varies, which enables to use a large number of micro bubbles (for
10 example, fine bubbles) as a core of cavitation. Accordingly, the frequency sweep
function possessed by the ultrasonic generator 20 further improves the treatment efficiency
of the ultrasonic treatment apparatus 1 according to the present embodiment.
[0038]
Meanwhile, as a general property of ultrasonic waves, a phenomenon that “when a
15 wavelength of the ultrasonic waves becomes 1/4 of a wavelength corresponding to a
thickness of an irradiation object, the ultrasonic wave transmits through the irradiation
object”, is known. Therefore, by applying ultrasonic waves while sweeping the
frequency within a proper range, it is possible that, when the object to be treated is a
tubular body or the like having a hollow portion, for example, ultrasonic waves transmitted
20 into the tubular body can be increased, resulting in that the treatment efficiency of the
ultrasonic treatment apparatus 1 according to the present embodiment is further improved.
[0039]
Here, when the transmittance of ultrasonic waves at a surface of the irradiation
object is considered, the ultrasonic waves are vertically incident on the irradiation object,
25 and not only that, they propagate while repeating multiple reflection, and thus a fixed
sound field is unlikely to be formed. Nonetheless, in order to create a condition of
18
making ultrasonic waves transmit through a wall surface of the irradiation object, it is
preferable to realize a frequency capable of satisfying a condition that “a wavelength of the
ultrasonic waves becomes 1/4 of a wavelength corresponding to a thickness of the object to
be treated”, no matter where the object to be treated is positioned. When the present
5 inventors conducted studies regarding a range of such a frequency, it has been clarified that
by applying ultrasonic waves while sweeping the frequency within a range of ±0.1 kHz to
±10 kHz centered on a certain selected frequency, it is possible to realize the transmittance
of ultrasonic waves as described above. Based on these reasons, the ultrasonic generator
20 preferably has a frequency sweep function capable of applying ultrasonic waves while
10 sweeping the frequency within a range of ±0.1 kHz to ±10 kHz centered on a certain
selected frequency of ultrasonic waves.
[0040]

The circulation path 30 is a path for circulating the treatment liquid 3 contained in
15 the treatment tank 10. As illustrated in FIG. 1A, this circulation path 30 has at least the
circulating pump 31 for circulating the treatment liquid 3, the treatment liquid extraction
pipe 33 that connects the treatment liquid 3 extracted from the treatment tank 10 to the
circulating pump 31, and the treatment liquid discharge pipe 35 that discharges the
treatment liquid 3 passed through the circulating pump 31 to the treatment tank 10.
20 Further, as illustrated in FIG. 1A, the fine bubble generator 40 is provided in series with
the treatment liquid extraction pipe 33, performs deaeration on the treatment liquid 3
extracted from the treatment tank 10, and generates fine bubbles in the treatment liquid 3.
[0041]
Here, it is set that, for the circulating pump 31, a general-purpose pump such as,
25 for example, a centrifugal pump or a diaphragm pump is used, and a special pump such as
a vacuum pump, a pressure-reducing pump, or a pressure pump is not used.
19
[0042]
The fine bubble generator 40 is provided in the middle of the treatment liquid
extraction pipe 33 under a negative pressure environment. By the fine bubble generator
40, fine bubbles are generated in the treatment liquid 3 extracted from the treatment tank
5 10. Note that when the fine bubble generator 40 is provided in the middle of, not the
treatment liquid extraction pipe 33, but the treatment liquid discharge pipe 35 under a
positive pressure environment, the deaeration of the treatment liquid 3 cannot be
performed, resulting in that desired fine bubbles cannot be generated.
[0043]
10 Here, an average bubble diameter of the fine bubbles generated in the treatment
liquid 3 to be discharged to the treatment tank 10, by the fine bubble generator 40, is
preferably 1 μm to 100 μm. Here, the average bubble diameter is a diameter with the
maximum number of samples in a number distribution regarding diameters of fine bubbles.
When the average bubble diameter is less than 1 μm, there is a case where the fine bubble
15 generator 40 becomes large in size, and it becomes difficult to supply fine bubbles after
adjusting bubble diameters. The average bubble diameter is more preferably 2 μm or
more, and still more preferably 3 μm or more. This makes it possible to more securely
realize the supply of fine bubbles after adjusting the bubble diameters. On the other hand,
when the average bubble diameter exceeds 100 μm, a floating speed of fine bubbles is
20 increased, which shortens a lifetime of fine bubbles in a cleaning liquid, and realistic
cleaning cannot be performed in some cases. Further, when the bubble diameter is
excessively large, the propagation of ultrasonic waves is inhibited by fine bubbles, which
sometimes reduces the effect of improving cleaning power of ultrasonic waves. The
average bubble diameter is more preferably 90 μm or less, still more preferably 80 μm or
25 less, and yet still more preferably 70 μm or less. This makes it possible to further
securely prevent the reduction of the effect of improving the cleaning power of ultrasonic
20
waves.
[0044]
Further, a bubble number density of fine bubbles in the treatment liquid 3 to be
discharged to the treatment tank 10 by the fine bubble generator 40, is preferably 1 × 103
5 pieces/mL to 1 × 1010 pieces/mL. When the bubble number density of fine bubbles is less
than 103 pieces/mL, the ultrasonic propagation property improving action by fine bubbles
cannot be sufficiently obtained in some cases, and further, the core of ultrasonic cavitation
required for the treatment becomes fewer, which is not preferable. The bubble number
density of fine bubbles is more preferably 1 × 103 pieces/mL or more, still more preferably
10 5 × 103 pieces/mL or more, and yet still more preferably 1 × 104 pieces/mL or more.
Accordingly, it becomes possible to make the ultrasonic propagation property improving
action by fine bubbles exhibit more securely. On the other hand, the bubble number
density of fine bubbles exceeding 1 × 1010 pieces/mL is not preferable since the fine bubble
generator 40 becomes large in size or the number of fine bubble generators 40 is increased,
15 and thus the supply of fine bubbles is not realistic in some cases. The bubble number
density of fine bubbles is more preferably 1 × 109 pieces/mL or less, still more preferably 1
× 108 pieces/mL or less, and yet still more preferably 1 × 107 pieces/mL or less.
[0045]
Note that when performing an operation using the ultrasonic treatment apparatus 1
20 according to the present embodiment, it is preferable that control is performed so that the
bubble number density of fine bubbles in the treatment liquid contained in the treatment
tank 10 coincides with the bubble number density of fine bubbles in the treatment liquid 3
to be discharged to the treatment tank 10, and then various types of treatments as described
above are performed.

What Is Claimed is
[Claim 1]
An ultrasonic treatment apparatus, comprising:
a treatment part capable of accommodating a treatment liquid and an object to be
5 treated;
an ultrasonic generator that is provided in the treatment part and applies ultrasonic
waves to the object to be treated; and
a circulation path for circulating the treatment liquid in the treatment part,
wherein:
10 the circulation path has a circulating pump for circulating the treatment liquid, a
treatment liquid extraction pipe that connects the treatment liquid extracted from the
treatment part to the circulating pump, and a treatment liquid discharge pipe that
discharges the treatment liquid passed through the circulating pump to the treatment part;
and
15 a fine bubble generator which performs deaeration on the extracted treatment
liquid and generates fine bubbles in the treatment liquid, is provided to the circulation path,
in series with the treatment liquid extraction pipe, wherein
the fine bubble generator has two or more narrow portions each having an opening
flow path of the treatment liquid with a size narrower than an inside diameter of the
20 treatment liquid extraction pipe, in which the opening flow paths of the narrow portions
adjacent to each other are configured to prevent the treatment liquid from proceeding
straight, wherein:
regarding each of the narrow portions, when an opening cross-sectional area of the
inside diameter of the treatment liquid extraction pipe is set to A0, and an opening
25 cross-sectional area of the inside diameter of the treatment liquid extraction pipe at an i (i
is an integer of 1 or more)-th narrow portion from the treatment part side toward the
68
circulating pump side is represented as Ai, an opening cross-sectional area ratio Ri of the
i-th narrow portion represented as Ai/A0 satisfies the following formula (1); and
when an interval between the i-th narrow portion and an i+1-th narrow portion is
represented as Li, the following formula (2) is satisfied.
5 Ri = 0.10 to 0.50 ··· Formula (1)
1.0 ≤ Li/2(A0/π)0.5 ≤ 5.0 ··· Formula (2)
[Claim 2]
The ultrasonic treatment apparatus according to claim 1, wherein
when the treatment liquid extraction pipe is seen from a pipe axis direction,
10 positions of the opening flow paths of the narrow portions adjacent to each other are not
overlapped with each other.
[Claim 3]
The ultrasonic treatment apparatus according to claim 1 or 2, wherein:
a treatment tank which contains the treatment liquid is provided as the treatment
15 part; and
the ultrasonic generator indirectly applies ultrasonic waves to the object to be
treated via the treatment liquid.
[Claim 4]
The ultrasonic treatment apparatus according to claim 1 or 2, wherein
20 the ultrasonic generator directly applies ultrasonic waves to the object to be
treated that is immersed in the treatment liquid in the treatment part.
[Claim 5]
The ultrasonic treatment apparatus according to any one of claims 1 to 4, wherein
when the number of the narrow portions is set to N, and an N-th opening area ratio
25 from the treatment part side toward the circulating pump side is represented as RN, the
following formula (3) and formula (4) are satisfied.
69
Ri+1 ≥ Ri ··· Formula (3)
RN/R1 ≥ 1.10 ··· Formula (4)
[Claim 6]
The ultrasonic treatment apparatus according to any one of claims 1 to 5, wherein
5 the number N of the narrow portions is 2 to 10.
[Claim 7]
The ultrasonic treatment apparatus according to any one of claims 1 to 6,
comprising one or a plurality of the narrow portions each formed by a projecting member
projecting from an inner surface of the treatment liquid extraction pipe.
10 [Claim 8]
The ultrasonic treatment apparatus according to claim 7, comprising, as the
narrow portion, a movable projecting member projecting from the inner surface of the
treatment liquid extraction pipe.
[Claim 9]
15 The ultrasonic treatment apparatus according to any one of claims 1 to 8,
comprising one or a plurality of the narrow portions each formed by an opening member
provided with one or a plurality of through holes.
[Claim 10]
The ultrasonic treatment apparatus according to any one of claims 1 to 9, wherein
20 the ultrasonic generator can select a frequency of the ultrasonic waves from a
frequency band of 20 kHz to 200 kHz.
[Claim 11]
The ultrasonic treatment apparatus according to any one of claims 1 to 10,
wherein
25 the ultrasonic generator can apply ultrasonic waves to the treatment liquid while
performing a sweep within a range of ±0.1 kHz to ±10 kHz centered on a selected
70
frequency of the ultrasonic waves.
[Claim 12]
A fine bubble supply method, comprising supplying, when performing a
predetermined treatment on an object to be treated while applying ultrasonic waves to a
5 treatment part capable of accommodating a treatment liquid and the object to be treated,
the treatment liquid containing fine bubbles to the treatment part, wherein
an ultrasonic generator that is provided in the treatment part and applies ultrasonic
waves to the object to be treated, and a circulation path for circulating the treatment liquid
in the treatment part are provided with respect to the treatment part, wherein:
10 the circulation path has a circulating pump for circulating the treatment liquid, a
treatment liquid extraction pipe that connects the treatment liquid extracted from the
treatment part to the circulating pump, and a treatment liquid discharge pipe that
discharges the treatment liquid passed through the circulating pump to the treatment part;
and
15 a fine bubble generator which performs deaeration on the extracted treatment
liquid and generates fine bubbles in the treatment liquid, is provided to the circulation path,
in series with the treatment liquid extraction pipe, wherein
the fine bubble generator has two or more narrow portions each having an opening
flow path of the treatment liquid with a size narrower than an inside diameter of the
20 treatment liquid extraction pipe, in which the opening flow paths of the narrow portions
adjacent to each other are configured to prevent the treatment liquid from proceeding
straight, wherein:
regarding each of the narrow portions, when an opening cross-sectional area of the
inside diameter of the treatment liquid extraction pipe is set to A0, and an opening
25 cross-sectional area of the inside diameter of the treatment liquid extraction pipe at an i (i
is an integer of 1 or more)-th narrow portion from the treatment part side toward the
71
circulating pump side is represented as Ai, an opening cross-sectional area ratio Ri of the
i-th narrow portion represented as Ai/A0 satisfies the following formula (1); and
when an interval between the i-th narrow portion and an i+1-th narrow portion is
represented as Li, the following formula (2) is satisfied.
5 Ri = 0.10 to 0.50 ··· Formula (1)
1.0 ≤ Li/2(A0/π)0.5 ≤ 5.0 ··· Formula (2)
[Claim 13]
The fine bubble supply method according to claim 12, wherein
the fine bubble generator generates the fine bubbles to make a dissolved gas
10 amount to be 50% or less of a saturated dissolved gas amount in the treatment liquid to be
discharged to the treatment part.
[Claim 14]
The fine bubble supply method according to claim 12 or 13, wherein
the fine bubble generator generates the fine bubbles to make the fine bubbles
15 having an average bubble diameter of 1 μm to 100 μm exist at a bubble number density in
a range of 1 × 103 pieces/mL to 1 × 1010 pieces/mL in the treatment liquid to be discharged
to the treatment part.
[Claim 15]
The fine bubble supply method according to any one of claims 12 to 14, wherein
20 the ultrasonic generator selects a frequency of the ultrasonic waves from a
frequency band of 20 kHz to 200 kHz.
[Claim 16]
The fine bubble supply method according to any one of claims 12 to 15, wherein
the ultrasonic generator applies ultrasonic waves to the treatment liquid while
25 performing a sweep within a range of ±0.1 kHz to ±10 kHz centered on a selected
frequency of the ultrasonic waves.