U.S. patent application number 14/530875 was filed with the patent office on 2015-05-21 for liquid treatment unit, toilet seat with washer, washing machine, and liquid treatment apparatus.
The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to MASAKI FUJIKANE, SHIN-ICHI IMAI, MARI ONODERA.
Application Number | 20150136672 14/530875 |
Document ID | / |
Family ID | 53172221 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150136672 |
Kind Code |
A1 |
ONODERA; MARI ; et
al. |
May 21, 2015 |
LIQUID TREATMENT UNIT, TOILET SEAT WITH WASHER, WASHING MACHINE,
AND LIQUID TREATMENT APPARATUS
Abstract
A liquid treatment unit includes: a treatment tank provided with
an inlet and an outlet, the treatment tank having a shape that
allows a portion of liquid to be retained; a controller that
controls supply of liquid into the treatment tank and ejection of
liquid from the treatment tank; and a plasma generator generates
plasma in the liquid inside the treatment tank. The plasma
generator generates plasma while the controller stops supply of
liquid and ejection of liquid. After the liquid has been treated,
the controller resumes the supply of liquid, and causes the liquid
to be ejected from the treatment tank while allowing a portion of
the treated liquid to be retained inside the treatment tank.
Inventors: |
ONODERA; MARI; (Osaka,
JP) ; FUJIKANE; MASAKI; (Osaka, JP) ; IMAI;
SHIN-ICHI; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
53172221 |
Appl. No.: |
14/530875 |
Filed: |
November 3, 2014 |
Current U.S.
Class: |
210/192 ; 4/233;
68/13R |
Current CPC
Class: |
C02F 1/4608 20130101;
A47K 13/302 20130101; C02F 2303/04 20130101; C02F 2307/12 20130101;
C02F 2305/023 20130101 |
Class at
Publication: |
210/192 ;
68/13.R; 4/233 |
International
Class: |
C02F 1/30 20060101
C02F001/30; A47K 13/30 20060101 A47K013/30 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 18, 2013 |
JP |
2013-238036 |
Claims
1. A liquid treatment unit comprising: a treatment tank provided
with an inlet and an outlet, the treatment tank having a shape that
allows a portion of liquid to be retained; a controller that
controls supply of liquid into the treatment tank and ejection of
liquid from the treatment tank; and a plasma generator that
generates plasma in the liquid inside the treatment tank, wherein
the plasma generator generates plasma to cause the liquid to be
treated while the controller stops supply of liquid and ejection of
liquid in a state where the liquid is present inside the treatment
tank, and after the liquid has been treated, the controller resumes
the supply of liquid into the treatment tank, and causes the liquid
to be ejected from the treatment tank while allowing a portion of
the treated liquid to be retained inside the treatment tank.
2. The liquid treatment unit according to claim 1, wherein, prior
to stopping the supply of liquid and the ejection of liquid, the
controller causes the liquid to be supplied into the treatment
tank.
3. The liquid treatment unit according to claim 1, wherein, when
the liquid is ejected while allowing a portion of the treated
liquid to be retained inside the treatment tank, the plasma
generator further generates the plasma in the liquid inside the
treatment tank.
4. The liquid treatment unit according to claim 1, wherein, when
the liquid is ejected while allowing a portion of the treated
liquid to be retained inside the treatment tank, the quantity of
the liquid ejected from the treatment tank is equal to or greater
than the volume of the treatment tank.
5. The liquid treatment unit according to claim 1, wherein a cross
section of the outlet is smaller than a cross section of an
internal space of the treatment tank.
6. The liquid treatment unit according to claim 5, wherein the
plasma generator generates a gas bubble, a cross section of the gas
bubble being smaller than the cross section of the internal space
of the treatment tank.
7. The liquid treatment unit according to claim 1, further
comprising: a circulation flow passage extending from the outlet to
the inlet; and a distributor that causes a portion of the liquid
ejected from the treatment tank to be recirculated to the treatment
tank through the circulation flow passage.
8. The liquid treatment unit according to claim 1, further
comprising: a gas-liquid separator provided in a flow passage
upstream or downstream from the treatment tank, the gas-liquid
separator extracting gas from a mixture of the liquid and gas and
emitting the gas to outside.
9. The liquid treatment unit according to claim 1, wherein the
plasma generator comprises: a first electrode at least a portion of
which is arranged inside the treatment tank; a second electrode at
least a portion of which is arranged inside the treatment tank; an
insulator surrounding the periphery of the first electrode with a
space therebetween, the insulator having an opening through which
the space communicates the inside of the treatment tank; a power
source that applies a voltage between the first electrode and the
second electrode; and a gas supply device that supplies gas to the
space.
10. The liquid treatment unit according to claim 9, wherein at
least part of the first electrode includes a region where a
conductor surface thereof is exposed, and wherein, when the region
is covered by the gas, the power source applies the voltage.
11. The liquid treatment unit according to claim 1, wherein the
plasma generator comprises: a first electrode at least a portion of
which is arranged inside the treatment tank; a second electrode at
least a portion of which is arranged inside the treatment tank; an
insulator surrounding the periphery of the first electrode with a
space therebetween, the insulator having an opening through which
the space communicates the inside of the treatment tank; and a
power source that applies a voltage between the first electrode and
the second electrode.
12. The liquid treatment unit according to claim 11, wherein at
least part of the first electrode includes a region where a
conductor surface thereof is exposed, and wherein the power source
applies the voltage, vaporizing liquid inside the space to produce
gas, and causing discharge when the region is covered by the
gas.
13. A toilet seat with a washer comprising: the liquid treatment
unit according to claim 1; and a washing nozzle to which the liquid
ejected from the treatment tank is supplied.
14. The toilet seat with a washer according to claim 13, further
comprising: an input part that receives an instruction of washing
from a user, wherein the controller stops the supply of liquid and
the ejection of liquid prior to receiving the instruction from the
input part, the plasma generator generates the plasma in the liquid
inside the treatment tank while the supply of liquid and the
ejection of liquid are stopped, and the controller, based on the
instruction from the input part, causes the liquid to be ejected to
the washing nozzle while allowing a portion of the treated liquid
to be retained inside the treatment tank.
15. A washing machine comprising: the liquid treatment unit
according to claim 1; and a washing tub to which the liquid ejected
from the treatment tank is supplied.
16. The washing machine according to claim 15, further comprising:
an input part that receives an instruction of starting washing from
a user, wherein the controller stops the supply of liquid and the
ejection of liquid on the basis of the instruction from the input
part, the plasma generator generates the plasma in the liquid
inside the treatment tank while the supply of liquid and the
ejection of liquid are stopped, and the controller, after the
liquid has been treated, causes the liquid to be ejected to the
washing tub while allowing a portion of the treated liquid to be
retained inside the treatment tank.
17. A liquid treatment apparatus comprising: the liquid treatment
unit according to claim 1; and a water inlet to which the liquid
ejected from the treatment tank is supplied, the liquid treatment
apparatus being the one selected from the group consisting of a
water purifying apparatus, an air conditioner, a humidifier, an
electric shaver washer, a dish washer, a processing apparatus for
hydroponic culture, and an apparatus for circulating nourishing
solution.
18. A liquid treatment unit comprising: a treatment tank provided
with an inlet and an outlet, the treatment tank having a shape that
allows a portion of liquid to be retained; a plasma generator that
generates plasma in the liquid in a state where the liquid is
present inside the treatment tank; a circulation flow passage
extending from the outlet to the inlet; and a distributor that
causes a portion of the liquid ejected from the treatment tank to
be recirculated to the treatment tank through the circulation flow
passage.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2013-238036, filed on Nov. 18, 2013, the contents
of which are hereby incorporated by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to a liquid treatment unit, a
toilet seat with a washer, a washing machine, and a liquid
treatment apparatus.
[0004] 2. Description of the Related Art
[0005] Sterilizing apparatuses that use plasma to treat liquids
such as polluted water have been proposed. For example, in the
sterilizing apparatus disclosed in the specification of Japanese
Patent No. 4784624, a high-voltage electrode and a grounding
electrode are arranged with an interval therebetween in liquid
inside a treatment tank. In a sterilization treatment apparatus
configured in this manner, when a high-voltage pulse is applied
between both electrodes to cause electrical discharge, plasma is
generated in gas bubbles produced by the instantaneous boiling
phenomenon, producing radicals such as OH, H, O, O.sub.2.sup.-, and
O.sup.- and also H.sub.2O.sub.2, which destroys microorganisms and
bacteria.
SUMMARY
[0006] In apparatuses having a conventional configuration, there
has been a problem concerning liquid treatment efficiency.
[0007] The present disclosure provides a liquid treatment unit, a
toilet seat with a washer, a washing machine, and a liquid
treatment apparatus, with which liquids are treated in an efficient
manner.
[0008] A liquid treatment unit according to an aspect of the
present disclosure includes: a treatment tank provided with an
inlet and an outlet, the treatment tank having a shape that allows
a portion of liquid to be retained; a controller that controls
supply of liquid into the treatment tank and ejection of liquid
from the treatment tank; and a plasma generator generates plasma in
the liquid inside the treatment tank. The plasma generator
generates plasma to cause the liquid to be treated while the
controller stops supply of liquid and ejection of liquid in a state
where the liquid is present inside the treatment tank. After the
liquid has been treated, the controller resumes the supply of
liquid into the treatment tank and causes the liquid to be ejected
from the treatment tank while allowing a portion of the treated
liquid to be retained inside the treatment tank.
[0009] The liquid treatment unit, the toilet seat with a washer,
the washing machine, and the liquid treatment apparatus according
to the present disclosure are able to treat liquid in an efficient
manner.
[0010] Additional benefits and advantages of the disclosed
embodiments will be apparent from the specification and drawings.
The benefits and/or advantages may be individually provided by the
various embodiments and features of the specification and drawings,
and need not all be provided in order to obtain one or more of the
same.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic diagram depicting an example of the
overall configuration of a liquid treatment unit according to
embodiment 1 of the present disclosure.
[0012] FIG. 2 is a schematic diagram depicting an example of the
overall configuration of a modified example of the liquid treatment
unit according to embodiment 1 of the present disclosure.
[0013] FIG. 3 is a cross sectional view depicting an example of the
configuration of a treatment tank.
[0014] FIG. 4 is a flowchart depicting an example of steps executed
by a controller.
[0015] FIG. 5 is a schematic diagram depicting a modified example
of a first electrode and the configuration peripheral thereto in a
plasma generator in the liquid treatment unit according to
embodiment 1 of the present disclosure.
[0016] FIG. 6 is a drawing depicting the relationship between the
sampling time and the sterilization rate in the liquid treatment
unit according to working example 1 of the present disclosure.
[0017] FIG. 7 is a graph depicting, in a reference example, the
relationship between the sampling time and the sterilization rate
when Staphylococcus aureus solution is used as the liquid to be
treated.
[0018] FIG. 8 is a graph depicting, in a reference example, the
relationship between the sampling time and the sterilization rate
when E. coli solution is used as the liquid to be treated.
[0019] FIG. 9 is a schematic diagram depicting an example of the
top end of a first electrode and the configuration peripheral
thereto in a plasma generator in a liquid treatment unit according
to embodiment 2 of the present disclosure.
[0020] FIG. 10 is a schematic diagram depicting an example of a
first electrode and the configuration peripheral thereto in a
plasma generator in a liquid treatment unit according to embodiment
3 of the present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
(Underlying Knowledge Forming Basis of the Present Disclosure)
[0021] As described above, the sterilizing apparatus in the
specification of Japanese Patent No. 4784624 is configured with a
high-voltage electrode and a grounding electrode arranged in liquid
inside a treatment tank. In a sterilizing apparatus configured in
this manner, when electrical discharge is caused between the
high-voltage electrode and the grounding electrode, liquid is
vaporized by the instantaneous boiling phenomenon, and plasma is
generated therein. Then, in the sterilizing apparatus, radicals
produced by the plasma can collide with bacteria in the liquid, and
liquid treatment is thereby performed.
[0022] However, in conventional sterilizing apparatuses, it has
been difficult to cause radicals to collide with bacteria floating
in liquid. For example, in the case where the sterilizing apparatus
continuously treats liquid in a treatment tank while supplying
liquid thereinto and ejecting liquid therefrom, liquid is passed
therethrough tank only once. In such a case, there has been a
problem in that it is difficult to increase sterilization
efficiency. In other words, in conventional apparatuses, it is
difficult to cause the radicals in the liquid to collide
efficiently with the bacteria moving in the liquid, preventing
liquid from being treated in a short time.
[0023] Therefore, the inventors took these kinds of problems of the
conventional technology into consideration, and thus conceived of a
novel liquid treatment apparatus. A liquid treatment apparatus
constituting an aspect of the present disclosure is as follows.
[0024] A liquid treatment unit according to an aspect of the
present disclosure includes: a treatment tank provided with an
inlet and an outlet, the treatment tank having a shape that allows
a portion of liquid to be retained; a controller that controls
supply of liquid into the treatment tank and ejection of liquid
from the treatment tank; and a plasma generator that generates
plasma in the liquid inside the treatment tank. The plasma
generator generates plasma to cause the liquid to be treated while
the controller stops supply of liquid and ejection of liquid in a
state where the liquid is present inside the treatment tank. After
the liquid has been treated, the controller resumes the supply of
liquid into the treatment tank and causes the liquid to be ejected
from the treatment tank while allowing a portion of the treated
liquid to be retained inside the treatment tank.
[0025] According to the liquid treatment unit according to an
aspect of the present disclosure, while the supply of liquid and
the ejection of liquid are performed, a portion of the liquid which
has treated by plasma is retained inside the treatment tank due to
the shape thereof, and therefore comes into contact with the newly
supplied liquid in a mixed state. Radicals produced by the plasma
remain in the liquid being retained. In other words, the newly
supplied liquid come into contact with the radicals in the retained
liquid while passing through the treatment tank, and it is thereby
possible to continuously obtain liquid that has a sterilization
effect. For example, when liquid including germs and/or organic
matters is supplied into the treatment tank, the germs in the
liquid are killed and/or the organic matters in the liquid is
decomposed by the radicals remaining in the treatment tank.
[0026] In the liquid treatment unit according to an aspect of the
present disclosure, for example, prior to stopping the supply of
liquid and the ejection of liquid, the controller may cause the
liquid to be supplied into the treatment tank prior to stopping the
supply of liquid and the ejection of liquid.
[0027] As a result of the step in which the liquid is supplied into
the treatment tank, a state is reached where the liquid is present
inside the treatment tank.
[0028] In the liquid treatment unit according to an aspect of the
present disclosure, for example, when the liquid is ejected while
allowing a portion of the treated liquid to be retained inside the
treatment tank, the plasma generator may further generate the
plasma in the liquid inside the treatment tank.
[0029] In addition to the step in which the supply of liquid and
the ejection of liquid are stopped, plasma is generated in the
liquid inside the treatment tank also in the step in which the
supply of liquid and the ejection of liquid are performed. Thus,
after the supply of liquid is resumed, newly supplied liquid also
comes into contact with radicals produced by the newly generated
plasma. Thus, the sterilization effect improves.
[0030] In the liquid treatment unit according to an aspect of the
present disclosure, for example, when the liquid is ejected while
allowing a portion of the treated liquid to be retained inside the
treatment tank, the quantity of the liquid ejected from the
treatment tank may be equal to or greater than the volume of the
treatment tank.
[0031] Since a portion of the radicals remains in the treatment
tank, newly supplied liquid can come into contact with the radicals
that have already been produced in the treatment tank.
[0032] In the liquid treatment unit according to an aspect of the
present disclosure, for example, a cross section of the outlet may
be smaller than the cross section of the internal space of the
treatment tank.
[0033] This allows a portion of the liquid to be retained inside
the treatment tank while liquid passing therethrough. Thus, newly
supplied liquid can be brought into contact with liquid that has
already been treated.
[0034] In the liquid treatment unit according to an aspect of the
present disclosure, for example, the plasma generator may generate
a gas bubble, a cross section of the gas bubble being smaller than
the cross section of the internal space of the treatment tank.
[0035] This can inhibit liquid in the treatment tank from being
involved with the flow of gas bubble and ejected with the gas
bubble. In other words, while the liquid is ejected, a portion of
the liquid can be retained inside the treatment tank. As a result
of the shape, newly supplied liquid can be brought into contact
with liquid that has already been treated.
[0036] The liquid treatment unit according to an aspect of the
present disclosure, for example, may further include a circulation
flow passage extending from the outlet to the inlet, and a
distributor. The distributor causes a portion of the liquid ejected
from the treatment tank to be recirculated to the treatment tank
through the circulation flow passage.
[0037] The distributor recirculates a portion of the liquid, which
has ejected from the treatment tank, to the treatment tank. Since
radicals are present in the recirculated liquid, newly supplied
liquid can be treated by the radicals in the recirculated
liquid.
[0038] The liquid treatment unit according to an aspect of the
present disclosure, for example, may further include a gas-liquid
separator provided in a flow passage upstream or downstream from
the treatment tank, the gas-liquid separator extracting gas from a
mixture of the liquid and gas and emitting the gas to outside.
[0039] With a gas-liquid separator, the flow rate of the liquid
supplied into the treatment tank and/or the flow rate of the liquid
ejected from the treatment tank can be substantially increased.
[0040] In the liquid treatment unit according to an aspect of the
present disclosure, for example, the plasma generator may be
provided with: a first electrode at least a portion of which is
arranged inside the treatment tank; a second electrode at least a
portion of which is arranged inside the treatment tank; an
insulator surrounding the periphery of the first electrode with a
space therebetween, the insulator having an opening through which
the space communicates the inside of the treatment tank; a power
source that applies a voltage between the first electrode and the
second electrode; and a gas supply device that supplies gas to the
space. For example, at least part of the first electrode may
include a region where a conductor surface thereof is exposed, and
when the region is covered by the gas, the power source may apply
the voltage.
[0041] Thus, the plasma generator can produce radicals having a
long residence time. This enables newly supplied liquid to be
brought into contact with liquid that has already been treated. For
example, when the newly supplied liquid includes bacteria and/or
organic matters, residual radicals can collide with the bacteria
and/or organic matters in the liquid in an efficient manner.
[0042] In the liquid treatment unit according to an aspect of the
present disclosure, for example, the plasma generator may be
provided with: a first electrode at least a portion of which is
arranged inside the treatment tank; a second electrode at least a
portion of which is arranged inside the treatment tank; an
insulator surrounding the periphery of the first electrode with a
space therebetween, the insulator having an opening through which
the space communicates the inside of the treatment tank; and a
power source that applies a voltage between the first electrode and
the second electrode. For example, at least part of the first
electrode may include a region where a conductor surface thereof is
exposed, and the power source may apply the voltage, vaporizing
liquid inside the space to produce gas, and causing discharge when
the region is covered by the gas.
[0043] Thus, the plasma generator can produce radicals having a
long residence time. This enables newly supplied liquid to be
brought into contact with liquid that has already been treated. For
example, when the newly supplied liquid includes bacteria and/or
organic matters, residual radicals can collide with the bacteria
and/or organic matters in the liquid in an efficient manner.
[0044] A toilet seat with a washer according to an aspect of the
present disclosure, for example, includes the aforementioned liquid
treatment unit, and a washing nozzle to which the liquid ejected
from the treatment tank is supplied.
[0045] The toilet seat with a washer according to an aspect of the
present disclosure, for example, may further include an input part
that receives an instruction of washing from a user. The controller
may stop the supply of liquid and the ejection of liquid prior to
receiving the instruction from the input part, the plasma generator
may generate plasma in the liquid inside the treatment tank while
the supply of liquid and the ejection of liquid are stopped, and
the controller, based on the instruction from the input part, may
cause the liquid to be ejected to the washing nozzle while allowing
a portion of the treated liquid to be retained inside the treatment
tank.
[0046] A washing machine according to an aspect of the present
disclosure, for example, may be provided with the aforementioned
liquid treatment unit, and a washing tub to which the liquid
ejected from the treatment tank may be supplied.
[0047] The washing machine according to an aspect of the present
disclosure, for example, may further include an input part that
receives an instruction of starting washing from a user. The
controller may stop the supply of liquid and the ejection of liquid
on the basis of input from the input part, the plasma generator may
generate plasma in the liquid inside the treatment tank while the
supply of liquid and the ejection of liquid are stopped, and the
controller, after the liquid has been treated, may cause the liquid
to be ejected to the washing tub while allowing a portion of the
treated liquid to be retained inside the treatment tank.
[0048] A liquid treatment apparatus according to an aspect of the
present disclosure, for example, is a liquid treatment apparatus
that includes the aforementioned liquid treatment unit, and a water
inlet to which the liquid ejected from the treatment tank is
supplied. The liquid treatment apparatus is the one selected from
the group consisting of a water purifying apparatus, an air
conditioner, a humidifier, an electric shaver washer, a dish
washer, a processing apparatus for hydroponic culture, and an
apparatus for circulating nourishing solution.
[0049] A liquid treatment unit according to an aspect of the
present disclosure, for example, may be provided with: a treatment
tank provided with an inlet and an outlet, the treatment tank
having a shape that allows a portion of liquid to be retained; a
plasma generator that generates plasma in the liquid in a state
where the liquid is present inside the treatment tank; a
circulation flow passage extending from the outlet to the inlet;
and a distributor that causes a portion of the liquid ejected from
the treatment tank to be recirculated to the treatment tank through
the circulation flow passage.
[0050] Hereafter, embodiments of the present disclosure are
described with reference to the drawings. Note that in all of the
following drawings, the same reference numbers have been appended
to the same or corresponding portions, and there are cases where
redundant descriptions have been omitted.
[0051] Note that the embodiments described hereafter all represent
comprehensive or specific examples. The numerical values, the
shapes, the materials, the components, the arrangement of the
components, the mode of connection, the steps, and the order of the
steps and so forth given in the following embodiments are examples
and are not intended to limit the present disclosure. A plurality
of steps may be executed separately in time or may be executed at
the same time. Other steps may be inserted between the steps.
Components that are not described in the independent claims are
described as optional components.
Embodiment 1
Liquid Treatment Unit
[0052] FIG. 1 is a block diagram depicting an example of the
schematic configuration of a liquid treatment unit 100 according to
embodiment 1. FIG. 2 is a schematic diagram depicting an example of
the overall configuration of a liquid treatment unit 100a according
to a modified example of embodiment 1 of the present
disclosure.
[0053] The liquid treatment unit 100 according to embodiment 1
includes: a treatment tank 101 in which liquid is retained; an
inlet 107 that supplies liquid to the treatment tank 101; an outlet
108 that ejects liquid from the treatment tank 101; a plasma
generator 102; and a controller 118 that controls the flow rate of
each of the liquid that is ejected from the treatment tank 101 and
the liquid that is supplied into the treatment tank 101. The plasma
generator 102 generates plasma in liquid of at least a partial
region of the treatment tank 101. The plasma generator 102 includes
a first electrode 103, a second electrode 104, and a power source
105. In this liquid treatment unit 100, the plasma generator 102
generates plasma in the liquid inside the treatment tank 101 while
liquid is retained in the treatment tank 101, and thereby the
retained liquid therein is treated by the radicals that are
produced. When new liquid is supplied into the treatment tank 101
and a portion of the treated liquid is ejected from the treatment
tank 101, treated liquid is partially retained due to the shape of
the treatment tank 101. Therefore, the newly supplied liquid and
the treated liquid can be mixed. This allows the newly supplied
liquid to be treated effectively with radicals having a long
residence time in the treated liquid.
[0054] Note that "controls the flow rate of each of the liquid that
is ejected from the treatment tank and the liquid that is supplied
into the treatment tank" includes being able to selectively switch
between a mode in which liquid is ejected from the treatment tank
and a mode in which liquid is not ejected from the treatment tank,
and being able to selectively switch between a mode in which liquid
is supplied into the treatment tank and a mode in which liquid is
not supplied into the treatment tank. In other words, the
controller can control whether or not liquid is ejected from the
treatment tank, and whether or not liquid is supplied into the
treatment tank.
[0055] The liquid treatment unit 100 may additionally include a
gas-liquid separator 116 midway in a flow passage of the treatment
tank 101, as depicted in FIG. 2. The liquid treatment unit 100 may
include a distributor 106. The distributor 106 is provided midway
from the treatment tank 101 to the outlet 108. The distributor 106
controls the distribution ratio, with which liquid flowing from the
treatment tank 101 is distributed into liquid to be ejected to the
outlet 108 and liquid to be recirculated to the treatment tank 101.
In other words, the distributor 106 recirculates a portion of the
treated liquid to the treatment tank 101. Since radicals having a
long residence time are present in the recirculated liquid, the
liquid treatment unit 100 is able to treat liquid newly supplied
from the inlet 107, with these radicals.
[0056] When the liquid treatment unit 100 has the distributor 106,
it may be further has a pump 117 midway to the distributor 106 from
the treatment tank 101. The pump 117 causes liquid to be circulated
in a fixed direction. The liquid treatment unit 100 may have a pump
112 in the vicinity of the inlet 107, to supply liquid 113 into the
treatment tank 101. The liquid treatment unit 100 may have a
controller 118 that controls the flow rate of the liquid inside the
treatment tank 101.
[0057] Note that "controls the distribution ratio with which liquid
flowing from the treatment tank is distributed into liquid to be
ejected to the outlet and liquid to be recirculated to the
treatment tank" includes selectively switching between a mode in
which the liquid in the treatment tank is not ejected, and a mode
in which a portion of the liquid is ejected at a preset
distribution ratio from the liquid that flows into the distributor.
In other words, the distributor can recirculate a portion of the
liquid to the treatment tank and to eject the remaining liquid to
the outlet.
[0058] Hereafter, examples of the components that make up the
liquid treatment unit 100 are described.
<Treatment Tank>
[0059] FIG. 3 is a cross sectional view depicting an example of the
configuration of the treatment tank 101. The treatment tank 101 has
a shape with which it is possible to retain liquid. The treatment
tank 101 is provided with the inlet 107 that supplies the liquid
into the treatment tank 101, and the outlet 108 that ejects the
liquid from the treatment tank 101. In the example depicted in FIG.
3, the cross section (A in FIG. 3) of the outlet 108 provided in
the treatment tank 101 is smaller than the cross section (B in FIG.
3) of the internal space of the treatment tank 101. With this
shape, the treatment tank 101 depicted in FIG. 3 is able to cause a
portion of the liquid to be retained inside the treatment tank 101
when the liquid is supplied and/or ejected. When the plasma
generator 102 generates a gas bubble 109, the cross section (B in
FIG. 3) of the internal space of the treatment tank 101 may be
larger than the cross section (C in FIG. 3) of the gas bubble 109.
Thus, it is possible to inhibit the liquid in the treatment tank
from becoming involved with the flow of gas bubble and thereby
being ejected from the treatment tank 101 with the gas bubble 109.
In other words, a portion of the liquid can be retained inside the
treatment tank 101 when the liquid is ejected.
[0060] When the liquid treatment unit 100 has the distributor 106,
it may further include the pump 117 midway to the outlet 108 from
the treatment tank 101. The pump 117 causes liquid to be circulated
in a fixed direction. The method for circulating liquid is not
restricted to the pump 117. The liquid treatment unit 100 may have
the pump 112 in the vicinity of the inlet 107, the pump 112
supplying liquid 113 into the treatment tank 101. The treatment
tank 101 may be a material that does not react with liquid. For the
treatment tank 101 may be made of a material such as glass,
plastic, silicone, or metal.
[0061] In the present disclosure, "the cross section of the
internal space of the treatment tank" means the cross section
perpendicular to the flow direction of the liquid that passes
through the inside of the treatment tank. "A shape that allows a
portion of the liquid to be retained inside the treatment tank" may
be a shape in which the largest part of the cross section of the
internal space of the treatment tank is larger than the cross
section of the outlet, for example.
<Plasma Generator>
[0062] The plasma generator 102 generates plasma in liquid of at
least a partial region of the treatment tank 101. Thus, radicals
having a long residence time are produced in the liquid, and
therefore the liquid retained in the treatment tank 101 is treated
with radicals. There may be a plurality of the plasma generators
102, each of which is located in the treatment tank 101. The plasma
generator 102 may be provided at the side near to the inlet 107 or
at the side near to the outlet 108 in the treatment tank 101. The
plasma generator 102, for example, may include: a first electrode
103 at least a portion of which is arranged inside the treatment
tank 101; a second electrode 104 at least a portion of which is
arranged inside the treatment tank 101; and a power source 105 that
applies a voltage between the first electrode 103 and the second
electrode 104.
<First Electrode>
[0063] At least a portion of the first electrode 103 may be
arranged inside the treatment tank 101. The arrangement of the
first electrode 103 is not particularly restricted as long as the
first electrode 103 is arranged inside the treatment tank 101. The
first electrode 103, for example, is formed from a material such as
iron, tungsten, copper, aluminum, platinum, or an alloy including
one or more metals selected from these metals. In order to prolong
the electrode life span, yttrium oxide added with a conductive
material may be thermally sprayed in a portion of the surface of
the first electrode 103. Yttrium oxide added with a conductive
material may have electric resistivity of 1 to 30 .OMEGA.cm, for
example. The shape of the first electrode 103, for example, may be
tubular, or cylindrical, with an opening at one end thereof that
faces the treatment tank 101. However, the first electrode 103 is
not limited to this shape.
<Second Electrode>
[0064] At least a portion of the second electrode 104 may be
arranged inside the treatment tank 101. The arrangement of the
second electrode 104 is not particularly restricted as long as the
second electrode 104 is arranged inside the treatment tank 101. The
second electrode 104 may be formed from a conductive metal
material. As with the first electrode 103, the second electrode
104, for example, is formed from a material such as iron, tungsten,
copper, aluminum, platinum, or an alloy including one or more
metals selected from these metals.
<Power Source>
[0065] The power source 105 is arranged between the first electrode
103 and the second electrode 104. The power source 105 applies a
high-frequency AC voltage between the first electrode 103 and the
second electrode 104. The frequency of the AC voltage may be 1 kHz
or greater, for example. The power source 105 may alternately apply
a positive pulse voltage and a negative pulse voltage, namely a
bipolar pulse voltage. By using a bipolar pulse voltage, it is
possible to prolong the life spans of the electrodes.
<Gas-Liquid Separator>
[0066] The liquid treatment unit 100 may additionally include the
gas-liquid separator 116 midway in a flow passage extending from
the treatment tank 101 to the distributor 106, as depicted in FIG.
2. The gas-liquid separator 116 extracts gas from a mixture of
liquid and gas in the flow passage and emits the gas to outside.
Thus, it is possible to increase the actual flow rate of the liquid
that is recirculated to the treatment tank 101.
<Controller>
[0067] The liquid treatment unit may have the controller 118, which
controls the flow rate of each of the liquid ejected from the
treatment tank 101 and the liquid supplied into the treatment tank
101. An example of a flowchart that includes steps executed by the
controller 118 is depicted in FIG. 4. The first step (S1) to the
third step (S3) described hereafter represent a series of liquid
treatment steps.
[0068] In the first step (S1), liquid is supplied into the
treatment tank 101 via the inlet 107. However, when liquid of a
specific quantity or more is already present inside the treatment
tank 101, the first step may be omitted.
[0069] After the first step, or in a state where liquid of a
specific quantity or more is present inside the treatment tank 101,
the second step (S2) is executed. In the second step (S2), the
supply of liquid into the treatment tank 101 via the inlet 107 and
the ejection of liquid from the treatment tank 101 via the outlet
108 are stopped. For example, the liquid supplied in the first step
remains inside the treatment tank 101 for a predetermined time. The
time of the second step may be appropriately set in accordance with
the length of the residence time of the radicals, the volume of the
treatment tank, the type and quantity of bacteria and/or organic
compounds in the liquid, and the flow rate of the liquid supplied
in the subsequent third step (S3), for example.
[0070] After the second step, in the third step (S3), a portion of
the liquid retained inside the treatment tank 101 is ejected
therefrom via the outlet 108, and newly liquid is supplied into the
treatment tank 101 via the inlet 107. At such time, the timing at
which the supply of liquid is started and the timing at which the
ejection of liquid is started do not have to coincide completely.
The flow rate of the liquid supplied or ejected and the period of
the third step may be appropriately set in accordance with the
length of the residence time of the radicals that are produced, the
volume of the treatment tank, the type and quantity of bacteria
and/or organic compounds in the liquid, for example.
[0071] In this case, in the second step, the plasma generator 102
generates plasma in the liquid inside the treatment tank 101, to
produce radicals, thereby causing the liquid to be treated.
[0072] The second step and the subsequent third step may be
executed once again after a predetermined quantity of liquid has
been ejected in the third step. Alternatively, the second step and
the third step may be repeatedly executed.
[0073] Note that in the present disclosure, when "the supply of
liquid into the treatment tank is resumed", the liquid may be the
same type of liquid as the liquid that has been supplied to the
treatment tank prior thereto, or may be different liquid. For
example, the liquid supplied into the treatment tank in the first
step may be pure water or tap water, and the liquid supplied into
the treatment tank in the third step may be polluted water that
includes bacteria and/or organic matters.
[0074] The plasma generator 102 may generate plasma in the liquid
inside the treatment tank 101 in the first step and/or the third
step in addition to the second step. For example, as a result of
plasma being generated in the third step in addition the second
step, the liquid that is newly supplied in the third step is able
to come into contact also with radicals that are newly produced by
the plasma generated in the third step. Thus, the sterilization
rate can improve.
[0075] In the third step, the controller may eject liquid of a
volume equal to or greater than that of the treatment tank 101.
When liquid of a volume equal to or greater than that of the
treatment tank 101 is ejected, the ejected liquid inevitably
includes the liquid that is newly supplied in the third step. When
the residence time of the radicals produced by the plasma is long,
the liquid that is newly supplied in the third step is able to come
into contact with the radicals to a greater extent, thereby
enabling liquid to be ejected in a sufficiently sterilized
state.
[0076] The controller 118 may recirculate at least a portion of the
liquid with the distributor 106, the portion of the liquid having
supplied into the treatment tank 101 in the first step or the third
step and ejected therefrom in the third step.
[0077] The controller 118 supplies liquid into the treatment tank
101 in the first step, and performs plasma treatment while the
liquid is retained inside the treatment tank 101 in the second
step. Germs present in the liquid inside the treatment tank 101 are
killed and/or organic matters present in the liquid inside the
treatment tank 101 is decomposed by active species including
radicals produced by the plasma. In this case, a portion of the
radicals remain in the liquid. When the supply of newly liquid and
the ejection of the treated liquid are performed in the third step,
a portion of the liquid that has been treated in the second step is
retained inside the treatment tank 101 due to the shape of the
treatment tank 101. In other words, a portion of the liquid that
has been treated in the second step comes into contact with the
newly supplied liquid, in a mixed state inside the treatment tank
101. As previously mentioned, radicals produced by the plasma
remain in the retained liquid. As a result, the newly supplied
liquid can come into contact with the radicals in the liquid
retained inside the treatment tank 101, thus causing a
sterilization effect.
[0078] The first step to the third step may be directly executed by
the controller 118, or may be indirectly executed based on an
instruction from the controller 118. For example, when liquid is to
be supplied into the treatment tank 101 via the inlet 107, the
controller 118 may operate the pump 112 provided at the inlet 107
to supply the liquid into the treatment tank 101. For example, the
controller 118 may cause liquid to be ejected from the treatment
tank 101 via the outlet 108, thereby causing liquid to be supplied
in a quantity that is approximately the same as the quantity
ejected into the treatment tank 101 via the inlet 107 because of
changes in pressure inside the treatment tank 101. For example, the
controller 118 may cause liquid to be supplied into the treatment
tank 101 via the inlet 107, thereby causing liquid to be ejected in
a quantity that is approximately the same as the quantity supplied
from the treatment tank 101 via the outlet 108 because of changes
in pressure inside the treatment tank 101.
<Distributor>
[0079] The liquid treatment unit 100 may include the distributor
106 outside of the treatment tank 101. The distributor 106 is
provided in a circulation flow passage extending from the outlet
108 toward the inlet 107. The distributor 106 controls the
distribution ratio, with which liquid has been ejected from the
treatment tank 101 via the outlet 108 is distributed into liquid to
be ejected via an ejection part of the liquid treatment unit 100
and liquid to be recirculated into the treatment tank 101. The
distributor 106 is able to be realized by using a distribution
valve, for example.
(Modified Example of a Plasma Generator)
[0080] Next, a modified example of a first electrode 103a and the
configuration peripheral thereto, which are included in the plasma
generator 102 of the liquid treatment unit 100 according to
embodiment 1, is described.
[0081] FIG. 5 is a cross sectional view depicting a modified
example of the first electrode 103a and the configuration
peripheral thereto, that are included in the plasma generator 102.
As depicted in FIG. 5, the first electrode 103a has an electrode
portion 121 at one end side and a support portion 122 at the other
end side. The electrode portion 121 is arranged inside the
treatment tank 101. The support portion 122 is connected and fixed
to a holding block 120, and is also connected to the power source
105. The support portion 122 may be a metal screw, for example. The
electrode portion 121 is formed from a columnar conductor, for
example. Columnar, for example, is a shape in which the diameter
from one end to the other end of the electrode portion 121 does not
change substantially. As result of employing this kind of shape,
compared to a shape that becomes thinner toward the tip and has no
substantial thickness at the endmost section such as a needle
shape, it is possible to suppress an excessive concentration in the
electric field toward the top end, and it is possible to suppress
deterioration due to use. An insulator 128 is provided with a space
124 between the insulator 128 and the electrode portion 121. The
insulator 128 has an opening 125 at one end side thereof, which is
located inside the treatment tank 101. A through hole 123 is
provided inside the support portion 122. A gas supply device (not
depicted) is connected to the through hole 123. Gas 129 supplied
from the gas supply device is supplied to the space 124 via the
through hole 123. When the gas 129 is supplied to the space 124, a
gas bubble 109 is generated in the liquid via the opening 125.
[0082] In the first electrode 103a, the electrode portion 121 and
the support portion 122 may have different sizes, and may be formed
from metal electrodes of different materials. As an example, the
electrode portion 121 may have a diameter of 0.95 mm and tungsten
may be used as the material therefor, and the support portion 122
may have a diameter of 3 mm and iron may be used as the material
therefor. Here, the diameter of the electrode portion 121 may be 2
mm or less, for example, as long as it is a diameter at which
plasma is generated. The material of the electrode portion 121 is
not restricted to tungsten, and another plasma-resistant metal
material may be used. For the material of the electrode portion
121, although there is deterioration in durability, copper,
aluminum, iron, or an alloy thereof may be used, for example.
Yttrium oxide added with a conductive material may be thermally
sprayed in a portion of the surface of the electrode portion 121.
Yttrium oxide added with a conductive material has electric
resistivity of 1 to 30 .OMEGA.cm, for example. The electrode life
span is prolonged by thermally spraying this yttrium oxide. The
diameter of the support portion 122 is not restricted to 3 mm, and
it is sufficient as long as that dimension is greater than the
diameter of the electrode portion 121. The material of the support
portion 122 is a metal material that is easy to process, and may be
copper, zinc, aluminum, tin, or brass or the like, which are
materials that are used for typical screws. The first electrode
103a is able to be formed by pressing the electrode portion 121
into the support portion 122 to thereby form a single unit, for
example. In this way, since a highly plasma-resistant metal
material is used for the electrode portion 121, and an easily
processable metal material is used for the support portion 122, it
is possible to realize a first electrode 103a having stable
characteristics that has low manufacturing costs while also being
plasma resistant.
[0083] The support portion 122 may have the through hole 123 that
passes through to the gas supply device (not depicted). The through
hole 123 is connected to the space 124, and the gas 129 from the
gas supply device is supplied to the space 124 via the through hole
123. The electrode portion 121 is then covered by the gas 129
supplied from the through hole 123. When electrode portion 121 has
a single through hole 123, the through hole 123 is located at the
lower side of the electrode portion 121 in the gravity direction as
depicted in FIG. 5, thereby causing the electrode portion 121 to be
covered by the gas 129 easily. When electrode portion 121 has a
single through hole 123 two or more through holes 123, it is
possible to suppress pressure loss in the through holes 123. The
diameter of the through hole 123 is 0.3 mm, for example.
[0084] A screw 126 may be provided at the outer periphery of the
support portion 122. For example, if the screw 126 at the outer
periphery of the support portion 122 is a male screw, the holding
block 120 may have a screw 127 that is a female screw. Thus, the
screws 126 and 127 can be screwed together, and thereby the first
electrode 103a can be fixed to the holding block 120. By rotating
the support portion 122, it is possible to accurately adjust the
position of the end surface of the electrode portion 121 related to
the opening 125 of the insulator 128. The first electrode 103a may
be connected to the power source 105 with the screw 126. Thus, the
contact resistance of the power source 105 and the first electrode
103a can stabilize, and thus the characteristics of the first
electrode 103a can stabilize. When the gas supply device (not
depicted) and the first electrode 103a are connected and fixed with
the screw 126, the connection therebetween can be implemented in a
reliable manner. This kind of arrangement is related to
waterproofing measures and safety measures when put into practical
use.
[0085] The method for holding the electrode portion 121 is not
limited to the aforementioned. It is sufficient as long as the gas
bubble can be formed in liquid from the opening 125 of the
insulator 128 by supplying the gas 129 to the space 124.
[0086] The insulator 128, which has an internal diameter of 1 mm,
for example, is arranged around the periphery of the electrode
portion 121 with the space 124 between the electrode portion 121
and the insulator 128. In the space 124, the gas 129 is supplied
from the gas supply device, and thereby the electrode portion 121
is covered by the gas 129. Therefore, the outer periphery of the
electrode portion 121 does not come into direct contact with liquid
even though the metal of the electrode is exposed. The opening 125
is provided in the insulator 128, and has the function of
determining the size of the gas bubble 109 when the gas bubble 109
is generated in the liquid inside the treatment tank 101. The
insulator 128 may be formed from a material such as aluminum oxide,
magnesium oxide, yttrium oxide, insulative plastic, glass, or
quartz.
[0087] The opening 125 of the insulator 128 may be arranged in the
liquid inside the treatment tank 101. In other words, although the
opening 125 is provided at the end surface of the insulator 128 as
depicted in FIG. 2, the opening 125 may be provided at the side
surface of the insulator 128. A plurality of openings 125 may be
provided in the insulator 128. The diameter of the opening 125 is 1
mm, as an example.
[0088] The second electrode 104 may be made of conductive metal
materials; for example, copper, aluminum, or iron or the like, but
is not limited to this.
[0089] A pump may be used as the gas supply device, for example.
Air, He, Ar, or O.sub.2 or the like is used for the gas 129 that is
supplied, for example. The flow rate may be selected from the range
of 0.5 L/min. to 2.0 L/min., for example, but is not limited to
this.
[0090] The power source 105 applies a pulse voltage or an AC
voltage between the first electrode 103a and the second electrode
104.
(Production of Radicals)
[0091] The production of radicals by the plasma generator 102
according to the modified example depicted in FIG. 5 will now be
described.
[0092] The gas supply device (not depicted) supplies the gas 129 to
the space between the first electrode 103a and the insulator 128 in
a state where liquid is present inside the treatment tank 101. The
gas 129 is emitted into the liquid inside the treatment tank 101
via the opening 125 of the insulator 128. At such time, a columnar
gas bubble that covers the electrode portion 121 of the first
electrode 103a is formed in the liquid. The gas bubble is a single
large gas bubble extending from the opening 125 of the insulator
128 for a specific distance (10 mm or more, for example). In other
words, since the gas 129 flows into the space 124 between the
electrode portion 121 of the first electrode 103a and the insulator
128, the electrode portion 121 of the first electrode 103a is
ordinarily covered by the gas 129. At such time, the surface of the
electrode portion 121 of the first electrode 103a does not come
into direct contact with the liquid.
[0093] Note that in the present disclosure, "the surface of the
first electrode does not come into direct contact with the liquid"
refers to the surface of the first electrode not coming into
contact with a large mass of liquid inside the treatment tank.
Therefore, for example, the state where "the surface of the first
electrode does not come into direct contact with the liquid"
includes the state where the surface of the first electrode is wet
with liquid (strictly speaking, the surface of the first electrode
is in contact with the liquid) and covered by the gas inside the
gas bubble. It is possible for this kind of state to occur, for
example, when a gas bubble is generated while the surface of the
first electrode is wet with liquid.
[0094] As mentioned above, after the surface of the electrode
portion 121, or exposed conductor portion, of the first electrode
103a has been covered by a gas bubble, the power source 105 applies
a high-frequency AC voltage or a pulse voltage between the first
electrode 103a and the second electrode 104. This causes an
electrical discharge inside the gas bubble in the vicinity of the
first electrode 103a, and thereby plasma is generated. The voltage
value or the current value output by the power source 105 may be a
value of a range with which glow discharge is generated. Although
the plasma spreads to the entirety of the gas bubble, highly
concentrated plasma is formed particularly in the vicinity of the
first electrode 103a. Radicals and so forth that sterilize the
liquid and/or decompose chemical substances included in the liquid
are produced by the plasma. There are no particular limitations
regarding the distance between the first electrode 103a and the
second electrode 104.
[0095] According to the modified example of the plasma generator
102 depicted in FIG. 5, radicals having a long residence time can
be produced. To be specific, it has been confirmed that it is
possible to produce OH radicals having a life span of approximately
10 min. from the generation of plasma being stopped. The life span
of the OH radicals is the half-life of the OH radical quantity
calculated by measuring the OH radical quantity at each
predetermined time using the electron spin resonance (ESR) method
after the plasma has stopped.
(Liquid Treatment Method)
[0096] An example of a liquid treatment method in which the liquid
treatment unit 100 according to embodiment 1 is used will now be
described.
[0097] (1) First, the inside of the treatment tank 101 is filled
with liquid (first step).
[0098] (2) Next, the plasma generator 102 generates plasma inside
the treatment tank 101 for a predetermined time while liquid is
retained inside the treatment tank 101, thus causing the retained
liquid to be treated (second step). Here, "liquid being retained
inside the treatment tank 101" refers to, for example, the state
where the supply of liquid into the treatment tank 101 and/or the
ejection of liquid from the treatment tank 101 has been stopped.
This treatment is referred to as prior plasma treatment. As a
result of this prior plasma treatment, the liquid retained in the
treatment tank 101 can be treated. Radicals having a long residence
time are present in the treated liquid.
[0099] (3) Next, at the same time that a portion of the liquid
retained in the treatment tank 101 is ejected from the treatment
tank 101 via the outlet 108, new liquid is supplied into the
treatment tank 101 via the inlet 107, thus causing liquid inside
the treatment tank 101 to be treated (third step).
[0100] A portion of the liquid to be treated may be supplied into
the treatment tank 101 in the first step, and the remaining liquid
to be treated may be supplied into the treatment tank 101 in the
third step. In this case, prior to performing the third step, the
prior plasma treatment is performed in advance for a portion of the
liquid to be treated.
[0101] In the liquid treatment unit 100 according to embodiment 1
of the present disclosure, since radicals having a long residence
time are produced in at least a portion of the treatment tank 101
by the plasma generator 102, the radicals and bacteria can be
brought into contact with each other for a long period of time
while the liquid is retained, thus causing the liquid to be
sterilized in an efficient manner. New liquid is supplied at the
same time that a portion of the liquid retained in the treatment
tank 101 is ejected. Many radicals remain in the treated liquid
that is retained in the treatment tank 101. Therefore, when new
liquid is supplied into the treatment tank 101, the newly supplied
liquid can be treated by the radicals having a long residence time
included in the treated liquid retained in the treatment tank
101.
[0102] The plasma may be generated inside the treatment tank 101 by
the plasma generator 102 in the third step in addition to the
second step. Thus, in the third step, when new liquid is supplied
into the treatment tank 101, the newly supplied liquid can be
treated by not only the radicals remaining in the treated liquid
retained in the treatment tank 101 but also by the radicals that
are newly produced by the plasma generator 102.
[0103] The plasma generator 102 that is able to produce radicals
having a long residence time is not limited to the configuration
indicated in embodiment 1 of the present disclosure. The inventors
have confirmed that it is possible to produce radicals having a
long residence time also in plasma generators having the
configurations described in embodiment 2 and embodiment 3 described
hereafter. A plasma generator having another configuration may be
effectively applied in the liquid treatment unit of the present
disclosure as long as radicals having a long residence time can be
produced.
Working Example 1
[0104] Working example 1 is an example in which the liquid
treatment according to the first step to the third step described
above is executed using a liquid treatment unit provided with: the
treatment tank 101 having a shape with which a portion of liquid
can be retained; and the plasma generator 102 having the first
electrode 103a and the configuration peripheral thereto depicted in
FIG. 5.
[0105] The liquid treatment unit 100a of working example 1 was as
depicted in FIG. 2. To be specific, the treatment tank 101 had a
volume of 70 mL.
[0106] The plasma generator 102 was as depicted in FIG. 5. To be
specific, the electrode portion 121 was made of tungsten, and the
diameter thereof was 0.95 mm. The support portion 122 was made of
iron, and the diameter thereof was 3 mm. The through hole 123 of
the support portion 122 had a diameter of 0.3 mm. The insulator 128
was formed from alumina ceramic, and had an internal diameter of 1
mm. The opening 125 provided in the insulator 128 had a diameter of
1 mm. The interval between the electrode portion 121 and the
insulator 128 was 0.05 mm. The distance between the first electrode
103 and the second electrode 104 was 10 mm. The second electrode
104 was made of tungsten, and the diameter was 1 mm. The gas supply
quantity supplied from the through hole 123 was 1 L/min. The power
source 105 that applies a voltage between the first electrode 103
and the second electrode 104 was capable of applying a pulse
voltage. The output capacity thereof was 80 VA, and for the peak
voltage at no load, a voltage of 10 kV was able to be applied.
[0107] The procedure for the liquid treatment method in working
example 1 is as follows.
[0108] (1) A portion of Staphylococcus aureus solution to be
treated was supplied into the treatment tank 101 (first step). The
bacteria quantity in the Staphylococcus aureus solution was
approximately 1.times.104 cfu/mL. The volume of the treatment tank
101 to which the Staphylococcus aureus solution was supplied was
approximately 70 mL.
[0109] (2) Next, the plasma generator 102 generated plasma inside
the treatment tank 101 for a predetermined time while liquid was
retained inside the treatment tank 101, and thereby the retained
liquid was treated (second step). This treatment is performed in
advance for a portion of the liquid to be treated, and is therefore
referred to as prior plasma treatment. As a result of this prior
plasma treatment, the liquid retained in the treatment tank 101 was
treated and sterilized, and radicals remained in the liquid.
[0110] (3) Next, while plasma was generated inside the treatment
tank 101 by the plasma generator 102, a portion of the liquid
inside the treatment tank 101 was ejected from the treatment tank
101 via the outlet 108, and also the remaining Staphylococcus
aureus solution was supplied into the treatment tank 101 via the
inlet 107, and thus liquid was then treated (third step). The
Staphylococcus aureus solution was supplied into the treatment tank
101 at a flow velocity of 0.5 L/min. The flow velocity of the
liquid ejected from the treatment tank 101 was 0.5 L/min, and the
quantity of the liquid was 250 mL. The liquid was treated for 20
seconds. At such time, treated liquid was retained in the treatment
tank 101 due to the shape thereof. Therefore, the newly supplied
liquid was mixed with the liquid retained inside the treatment tank
101. In this way, new liquid was supplied, and also a portion of
the treated liquid retained in the treatment tank 101 was mixed.
Thus, the newly supplied liquid was treated by using the residual
radicals included in the treated liquid retained in the treatment
tank 101, and the radicals that are sequentially generated by the
plasma generator 102.
[0111] FIG. 6 is a graph depicting the relationship between the
sterilization rate of Staphylococcus aureus in liquid obtained from
the outlet 108 and time. The horizontal axis in FIG. 6 indicates
elapsed time in which 0 seconds is immediately after the second
step has been started from the outlet 108. The vertical axis in
FIG. 6 indicates the sterilization rate. The period from 0 to 10
seconds is a period in which plasma treatment is performed in a
state where liquid is retained in the treatment tank 101 after both
the supply of liquid and the ejection of liquid are stopped, or in
other words, a second step period. The period from 10 seconds to 30
seconds is a period in which a portion of the liquid is ejected
while new liquid is supplied into the treatment tank 101 for liquid
to be treated, or in other words, a third step period. The period
from 30 seconds to 40 seconds indicates a second step period. The
period from 40 seconds to 60 seconds indicates a third step period.
As a result, as depicted in FIG. 6, solution having a sterilization
rate of 99% or more was continuously obtained.
[0112] In the period from 10 seconds to 30 seconds in which the
third step is executed, liquid of approximately 75 mL was ejected
in the first 9 seconds. That is, liquid of a quantity corresponding
to the total quantity of liquid treated by the prior plasma
treatment in the second step has already been ejected in the
10-second to 20-second stage of the third step. Therefore, the
sterilization rate is expected to decline thereafter because liquid
in which newly supplied liquid has been mixed is invariably
ejected. However, actually, a sterilization rate of approximately
99% or more was obtained even after 20 seconds. As mentioned above,
this is thought to be probably because the liquid retained in the
treatment tank 101 and the newly supplied liquid were mixed with
each other due to the treatment tank 101 having a shape which
allowed a portion of the liquid to be retained. In other words, the
newly supplied liquid was treated by using the radicals included in
the treated liquid retained in the treatment tank 101, and the
radicals sequentially generated by the plasma generator 102. Thus,
it is thought that it is possible to obtain a sterilization rate of
99% or more.
Reference Example
[0113] The reference example differs with working example 1 in that
the liquid treatment unit includes a flow passage tube that does
not have a shape with which a portion of the liquid can be
retained, instead of the treatment tank that has a shape which
allows a portion of the liquid to be retained. To be specific, the
flow passage tube of the reference example is able to retain all of
the liquid therein and to pass all of the liquid therethrough, but
is not able to pass a portion of the liquid while retaining the
remaining liquid. The capacity of the entirety of the flow passage
tube is 250 mL.
[0114] The specific liquid treatment procedure in the reference
example is as follows.
[0115] (1) First, a portion of the Staphylococcus aureus solution
or the E. coli solution to be treated flows into the flow passage
tube. In the case of the Staphylococcus aureus solution, the
bacteria quantity was approximately 1.times.104 cfu/mL. In the case
of the E. coli solution, the bacteria quantity was approximately
1.times.104 cfu/mL. The volume of the flow passage tube was
approximately 250 mL.
[0116] (2) Liquid was retained inside the flow passage tube and
prior plasma treatment was performed for a predetermined time. In
the case of the Staphylococcus aureus solution, prior plasma
treatment was performed for 10 min. or 15 min. In the case of the
E. coli solution, prior plasma treatment was performed for 20 min.
or 30 min.
[0117] (3) Next, while plasma was generated, together with liquid
being ejected from the flow passage tube, the Staphylococcus aureus
solution or the E. coli solution was supplied to the flow passage
tube for the liquid to be treated. In the case of the
Staphylococcus aureus solution and in the case of the E. coli
solution, the solution was supplied to the flow passage tube at a
flow velocity of 0.5 L/min. In the case of the Staphylococcus
aureus solution and in the case of the E. coli solution, the flow
rate of the liquid ejected from the flow passage tube was 0.5
L/min. At such time, the total quantity of the liquid was ejected
from the flow passage tube without being retained inside the flow
passage tube. Other conditions such as the power source and the
configuration of the plasma generator were the same as in working
example 1.
[0118] FIG. 7 is a graph depicting the relationship between the
sterilization rate obtained from the flow passage tube and time
when Staphylococcus aureus solution was used as the liquid to be
treated. FIG. 8 is a graph depicting the relationship between the
sterilization rate obtained from the flow passage tube and time
when E. coli solution was used as the liquid to be treated. The
horizontal axes in FIG. 7 and FIG. 8 indicate elapsed time in which
0 seconds is immediately after the ejection from the flow passage
tube has been started in the step of the aforementioned (3). The
vertical axes in FIG. 7 and FIG. 8 indicate the sterilization rate.
As depicted in FIG. 7 and FIG. 8, liquid for which prior plasma
treatment has been performed was ejected from 0 to 30 seconds, and
solution having a sterilization rate of 99% or more was
continuously obtained in each case. However, after 30 seconds,
newly supplied Staphylococcus aureus solution or E. coli solution
was ejected, and the sterilization rate deteriorated.
[0119] The flow passage tube used in the liquid treatment unit did
not have a shape which allows a portion of the liquid to be
retained, and therefore liquid that had been subjected to prior
plasma treatment was sequentially ejected from inside the flow
passage tube via the outlet 108. In this case, it is thought that
the treated liquid and the newly supplied liquid hardly mix because
the flow passage tube is not able to retain a portion of the
liquid. As a result, it is thought that, after 30 seconds during
which the total quantity of the liquid treated by the prior plasma
treatment has been ejected, it is no longer possible for bacteria
in the newly supplied liquid to be sufficiently killed with only
the radicals produced by the plasma generator 102.
Embodiment 2
[0120] In contrast with the liquid treatment unit according to
embodiment 1, the liquid treatment unit according to embodiment 2
is different with respect to the first electrode and the
configuration peripheral thereto in the plasma generator.
[0121] FIG. 9 is an enlarged view depicting an example of a first
electrode 103b and the configuration peripheral thereto, that are
part of a plasma generator in the liquid treatment unit according
to embodiment 2. The first electrode 103b is formed from metal, for
example. The first electrode 103b has a shape with openings at both
ends thereof, or hollow cylindrical shape, for example. A tubular
insulator 128 is arranged adhered to the outer peripheral surface
of the first electrode 103b. The insulator 128 is cylindrical, for
example. The insulator 128 is formed from alumina ceramic, for
example. The insulator 128 may be configured from titanium oxide,
for example.
[0122] A gas supply device is connected to the opening at one end
of the first electrode 103b. Gas 129 supplied from the gas supply
device passes through an internal space in the first electrode
103b, and is emitted into liquid as a gas bubble, from the opening
at the other end of the first electrode 103b. The insulator 128 may
be configured to be slidable with respect to the first electrode
103b.
[0123] With the aforementioned configuration, when gas is
continuously supplied to the opening at one end of the first
electrode 103b, a gas bubble is formed in the liquid, from the
opening at the other end of the first electrode 103b. The gas
bubble is a columnar gas bubble having dimensions such that the gas
therein covers the opening at the other end of the first electrode
103b, or in other words, the opening at the other end of the first
electrode 103b is positioned inside the gas bubble. The end surface
of the first electrode 103b, which is located in the vicinity of
the opening at the other end thereof, is not covered by the
insulator 128, and thus a conductor of the end surface is exposed.
Therefore, by using the gas supply device to appropriately set the
gas supply quantity, a state is maintained in which the vicinity of
the opening at the other end of the first electrode 103b is covered
by gas inside a gas bubble. In other words, the gas supply device
can supply the gas 129 to the first electrode 103b so that at least
the exposed conductor surface of the first electrode 103b is
positioned inside the gas bubble in the treatment tank 101. The
insulator 128 formed from alumina ceramic is arranged at the outer
peripheral surface of the first electrode 103b. Therefore, the
surface of the first electrode 103b is configured in such a way
that, due to the insulator 128 and the gas bubble, it is possible
to achieve a state where direct contact is not made with the
liquid.
[0124] The power source 105 applies a voltage between the first
electrode 103b and a second electrode 104 after a state is reached
where the exposed portion of the conductor of the first electrode
103b is positioned inside the gas bubble. The operation thereafter
is the same as in embodiment 1.
Embodiment 3
[0125] In contrast with the liquid treatment unit according to
embodiment 1, the liquid treatment unit according to embodiment 3
is different with respect to the first electrode and the
configuration peripheral thereto in the plasma generator. The
liquid treatment unit according to embodiment 3 does not have a gas
supply device.
[0126] FIG. 10 is a cross sectional view depicting an example of a
first electrode 103c and the configuration peripheral thereto that
form part of a plasma generator in the liquid treatment unit
according to embodiment 3. As depicted in FIG. 10, an insulator 128
surrounds the outer periphery of the first electrode 103c with a
space 124 therebetween. The insulator 128 has at least one opening
125 through which the space 124 communicates the inside of the
treatment tank 101. This configuration allows liquid inside the
treatment tank 101 to enter into the space 124 through the opening
125, and thus the space 124 is filled with the liquid. One end of
the first electrode 103c and one end of the insulator 128 are fixed
to a holding block 120. The method for fixing the first electrode
103c and the insulator 128 is not limited to this. A second
electrode 104 may be arranged in any position in the treatment tank
101, and there are no restrictions regarding the arrangement
position.
[0127] The operation of a plasma generator including the first
electrode 103c is as follows.
[0128] Prior to starting the liquid treatment, the space 124
between the first electrode 103c and the insulator 128 is filled
with liquid. In this state, a power source 105 applies a
high-frequency AC voltage or a pulse voltage between the first
electrode 103c and the second electrode 104, thereby heating the
liquid inside the space 124.
[0129] The temperature of the liquid inside the space 124 rises due
to the electrical power provided from the first electrode 103c.
This rise in temperature causes the liquid inside the space 124 to
vaporize, and thus gas is generated. The gas forms a mass while
gathering inside the space 124. Plasma is then generated due to
electrical discharge occurring inside the mass of gas, or in other
words, inside a gas bubble. Active species such as radicals are
produced by the plasma. This enables the liquid to be sterilized
and/or enables chemical substances in the liquid to be decomposed
by such gas bubbles.
[0130] In the liquid treatment units 100 and 100a according to
embodiments 1 to 3, radicals having a long residence time can be
produced in liquid inside the treatment tank 101 by the plasma
generator 102, and then the liquid including the radicals can be
retained inside the treatment tank 101. Thus, the radicals can be
brought into contact with bacteria in the liquid for a long period
of time, and thereby the liquid can be treated. Since a portion of
the treated liquid is retained in the treatment tank 101 while the
liquid is ejected, newly supplied liquid can be effectively treated
with the residual radicals included in the liquid retained in the
treatment tank 101.
[0131] In the liquid treatment units 100 and 100a according to
embodiments 1 to 3, the plasma generator 102 is arranged inside the
treatment tank 101. The plasma generator 102 has a configuration
with which a voltage is applied between the first electrode 103 and
the second electrode 104. With this configuration, the power source
105 applies a voltage between the first electrode 103 and the
second electrode 104, thereby generating plasma in the liquid
inside the treatment tank 101 to produce radicals having a long
residence time. Thus, bacteria present in the liquid retained
inside the treatment tank 101 can be treated.
[0132] In embodiments 1 to 3, descriptions have been given with
regard to examples in which bacteria present in the liquid inside
the treatment tank 101 are killed and/or organic matters present in
the liquid inside the treatment tank 101 is decomposed, and is not
limited to this. In the liquid treatment unit of the present
disclosure, the liquid inside the treatment tank 101 may not
include bacteria and/or organic matters. In other words, it is
sufficient as long as the liquid treatment unit of the present
disclosure has a configuration with which it is possible to produce
products such as radicals that are able to kill bacteria in liquid
and/or are able to decompose organic matters, and, in practice,
bacteria do not have to be eliminated in the liquid treatment unit
and organic matter does not have to be decomposed. Therefore,
"treat liquid" in the present disclosure may refer only to radicals
being produced in liquid, and whether bacteria in liquid are killed
and/or organic matters in liquid are decomposed may be
inconsequential. For example, the liquid treatment unit of the
present disclosure includes a mode in which liquid not including
bacteria or organic matters are supplied into a treatment tank, and
liquid including radicals is ejected from the treatment tank. The
"treatment efficiency of liquid" in the present disclosure may be
the efficiency at which liquid that includes radicals is
obtained.
[0133] With the liquid treatment unit of the present disclosure, by
combining with another device, it is possible to perform
sterilization in the other device using treated liquid ejected from
the treatment tank.
[0134] In the liquid treatment unit of the present disclosure, a
portion of liquid is ejected from the liquid inside the treatment
tank, and the remaining liquid is retained inside the treatment
tank. Thus, in the liquid treatment unit of the present disclosure,
radicals having a long life span can be continuously maintained in
the liquid retained inside the treatment tank and in the liquid
ejected from the treatment tank, even when liquid is newly
supplied. This is clear also from the experiment results depicted
in FIG. 6 to FIG. 8.
[0135] In embodiments 1 to 3, the first electrode 103 and the
configuration peripheral thereto are exemplified. Therefore, the
liquid treatment unit of the present disclosure is not limited to
the first electrode and the configuration peripheral thereto
indicated in embodiments 1 to 3, and various configurations can be
used. It is sufficient as long as the plasma generator 102 has a
configuration to produce products such as radicals that can
decompose bacteria in the liquid retained in the treatment tank
101.
Other Application Examples
[0136] The liquid treatment unit of the present disclosure may be
incorporated into a toilet seat with a washer. The toilet seat with
a washer includes a washing nozzle. Liquid ejected from the
treatment tank of the liquid treatment unit is supplied to the
washing nozzle. The toilet seat with a washer may include an input
part to receive input that instructs washing from a user. In this
case, the controller may execute the second step prior to the input
from the input part, and execute the third step and ejection the
liquid inside the treatment tank to the washing nozzle on the basis
of the input from the input part. The toilet seat with a washer may
include a sensor that detects the approach of a user. In this case,
the controller may execute the second step on the basis of the
sensor detection, and then execute the third step and eject the
liquid inside the treatment tank to the washing nozzle on the basis
of the input from the input part.
[0137] The liquid treatment unit of the present disclosure may be
incorporated into a washing machine. The washing machine includes a
washing tub. Liquid ejected from the treatment tank of the liquid
treatment unit is supplied to the washing tub. For example, the
washing machine may include an input part to receive input that
instructs the start of washing from a user. In this case, the
controller may, based on the input from the input part, execute the
first step, the second step and the third step, and thereby
ejecting the liquid inside the treatment tank to the washing tub.
For example, the controller may, based on the input from the input
part, execute the second step and, at the timing at which detergent
adhered to the clothing in the washing tub is rinsed out, execute
the third step and eject the liquid inside the treatment tank to
the washing tub.
[0138] The liquid treatment unit of the present disclosure may be
incorporated into a liquid treatment apparatus. The liquid
treatment apparatus includes a water inlet that is connected to the
ejection portion of the liquid treatment unit. The liquid treatment
apparatus is, for example, a water purifying apparatus, an air
conditioner, a humidifier, an electric shaver washer, a dish
washer, a processing apparatus for hydroponic culture, an apparatus
for circulating nourishing solution, a toilet seat with a washer, a
water purifier, a washing machine, an electric kettle, or an air
cleaner or the like.
[0139] Modes in which various modifications conceived by those
skilled in the art have been implemented in the present embodiments
or modified examples thereof, and modes constructed by combining
constituent elements in different embodiments or modified examples
thereof are also included in the scope of the present disclosure
provided they do not depart from the purpose of the present
disclosure. These comprehensive or specific aspects may be realized
by a method.
[0140] For example, a liquid treatment method may include: a step
in which supply of liquid to a treatment tank and ejection of
liquid from the treatment tank are stopped for a predetermined time
in a state where liquid is present inside the treatment tank; a
step in which plasma is generated in the liquid in the treatment
tank; and a step in which, after the step in which stopping is
performed, liquid is ejected from the treatment tank while liquid
is supplied into the treatment tank. The step in which stopping is
performed and the step in which the plasma is generated may be
performed at the same time. Note that in the present disclosure, a
plurality of steps being "performed at the same time" only refers
to there being a period in which the plurality of steps are
executed at the same time, and whether the start times and the end
times of the plurality of steps coincide may be inconsequential. In
the present disclosure, "B is performed while A is performed" only
refers to there being a period in which A and B are executed at the
same time, and whether the start times and the end times of A and B
coincide may be inconsequential.
[0141] For example, the liquid treatment method may additionally
include a step in which liquid is supplied into the treatment tank,
prior to the step in which stopping is performed.
[0142] For example, the step in which ejection is performed while
supply is performed, and the step in which the plasma is generated
may be performed at the same time.
[0143] For example, in the step in which ejection is performed
while supply is performed, liquid having a volume that is equal to
or greater than that of the treatment tank may be ejected.
[0144] For example, the liquid treatment method may additionally
include a step in which a portion of the liquid in the treatment
tank is recirculated to the treatment tank, and the remaining
liquid is ejected from the treatment tank.
[0145] For example, the liquid treatment method may additionally
include a step in which gas included in circulated liquid is
separated.
[0146] For example, the step in which the plasma is generated may
additionally include a step in which a voltage is applied between a
first electrode and a second electrode at least portions of which
are arranged inside the treatment tank.
[0147] For example, the step in which the plasma is generated may
additionally include a step in which gas is supplied into a space
formed between the first electrode and an insulator arranged around
the periphery of the first electrode, and the step in which a
voltage is applied may be executed in a state where an exposed
portion of a conductor, which is positioned inside the treatment
tank, of the first electrode is covered by the gas supplied in the
step in which gas is supplied.
[0148] For example, the step in which the plasma is generated may
additionally include a step in which, by applying a voltage between
the first electrode and the second electrode, liquid inside the
space formed between the first electrode and the insulator arranged
around the periphery of the first electrode is vaporized and gas is
produced, and the step in which a voltage is applied may be
executed in a state where the exposed portion of the conductor,
which is positioned inside the treatment tank, of the first
electrode is covered by the gas produced in the step in which gas
is produced.
[0149] For example, the liquid treatment method may additionally
include a step in which an instruction from the user is received,
after the step in which stopping is performed, prior to the step in
which ejection is performed while supply is performed.
[0150] For example, the liquid treatment method may additionally
include a step in which an instruction from the user is received,
prior to the step in which stopping is performed.
[0151] The liquid treatment unit according to the present
disclosure is useful in applications for a water purifying
apparatus, an air conditioner, a humidifier, an electric shaver
washer, a dish washer, a processing apparatus for hydroponic
culture, an apparatus for circulating nourishing solution, a toilet
seat with a washer, a water purifier, a washing machine, an
electric kettle, or an air cleaner or the like.
[0152] While the present disclosure has been described with respect
to exemplary embodiments thereof, it will be apparent to those
skilled in the art that the disclosure may be modified in numerous
ways and may assume many embodiments other than those specifically
described above. Accordingly, it is intended by the appended claims
to cover all modifications of the disclosure that fall within the
true spirit and scope of the disclosure.
* * * * *