U.S. patent application number 11/511046 was filed with the patent office on 2007-03-01 for fluid transportation system.
Invention is credited to Kusunoki Higashino, Yasuhiro Sando.
Application Number | 20070048155 11/511046 |
Document ID | / |
Family ID | 37804372 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070048155 |
Kind Code |
A1 |
Higashino; Kusunoki ; et
al. |
March 1, 2007 |
Fluid transportation system
Abstract
A fluid transportation system includes: a micropump provided
with a chamber and a diaphragm driven by an actuator; fluid
communication sections communicating with both ends of the chamber
of the micropump; a pressure absorbing section that is provided at
least one of the fluid communication sections so as to absorb or
reduce a fluid vibration pressure; and a narrow section that is
provided at a position further than the pressure absorbing section
from the chamber so as to narrow a flow path cross-section,
wherein, when R represents a flow path resistance value of the
narrow section and C represents an acoustic capacitance value of
the pressure absorbing section, a value obtained by multiplication
between R and C is not smaller than a driving cycle period value of
the micropump.
Inventors: |
Higashino; Kusunoki;
(Osaka-shi, JP) ; Sando; Yasuhiro; (Amagasaki-shi,
JP) |
Correspondence
Address: |
SIDLEY AUSTIN LLP
717 NORTH HARWOOD
SUITE 3400
DALLAS
TX
75201
US
|
Family ID: |
37804372 |
Appl. No.: |
11/511046 |
Filed: |
August 28, 2006 |
Current U.S.
Class: |
417/413.3 |
Current CPC
Class: |
F04B 53/1077 20130101;
F04B 43/043 20130101 |
Class at
Publication: |
417/413.3 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2005 |
JP |
2005-253219 |
Jun 6, 2006 |
JP |
2006-157492 |
Claims
1. A fluid transportation system, comprising: a micropump provided
with a chamber and a diaphragm driven by an actuator; fluid
communication sections communicating with both ends of the chamber
of the micropump; a pressure absorbing section that is provided at
least one of the fluid communication sections so as to absorb or
reduce a fluid vibration pressure; and a narrow section that is
provided at a position further than the pressure absorbing section
from the chamber so as to narrow a flow path cross-section,
wherein, when R represents a flow path resistance value of the
narrow section and C represents an acoustic capacitance value of
the pressure absorbing section, a value obtained by multiplication
between R and C is not smaller than a driving cycle period value of
the micropump.
2. The fluid transportation system of claim 1, wherein the narrow
section is disposed on the downstream side, along a transportation
direction, of the chamber.
3. The fluid transportation system of claim 1, wherein the
micropump transports fluid by repeatedly deforming the diaphragm;
and an acoustic capacitance of the pressure absorbing section has a
larger value than an acoustic capacitance of the chamber.
4. The fluid transportation system of claim 1, wherein at least one
wall surface of the pressure absorbing section comprises a thin
plate deformable by a fluid pressure; and a width of the thin plate
is larger than a width of the chamber.
5. The fluid transportation system of claim 1, wherein a flow path
resistance value of the narrow section is smaller than an effective
inner flow path resistance value of the micropump.
6. The fluid transportation system of claim 1, comprising a first
throttle flow path and a second throttle flow path at the both ends
of the chamber, of which respective flow path resistances change
corresponding to a differential pressure, wherein, a changing rate
of the flow path resistance of the first throttle flow path is
larger than that of the second throttle flow path; the actuator
transports fluid from the first throttle flow path toward the
second throttle flow path, by repeatedly increasing and decreasing
a pressure of fluid in the chamber in a first pattern where a time
of increasing the pressure is shorter than a time of decreasing the
pressure; and the actuator transports fluid from the second
throttle flow path toward the first throttle flow path, by
repeatedly increasing and decreasing the pressure of fluid in the
chamber in a second pattern where the time of increasing the
pressure is longer than the time of decreasing the pressure.
7. A fluid transportation system, comprising: a micropump provided
with a chamber and a diaphragm driven by an actuator; fluid
communication sections communicating with both ends of the chamber
of the micropump; a pressure absorbing section that is provided at
least one of the fluid communication sections so as to absorb or
reduce a fluid vibration pressure; and a filtering section having a
plurality of micro flow paths, the filtering section being provided
at a position further than the pressure absorbing section from the
chamber, wherein, when R represents a flow path resistance value of
the filtering section and C represents an acoustic capacitance
value of the pressure absorbing section, a value obtained by
multiplication between R and C is not smaller than a driving cycle
period value of the micropump.
8. The fluid transportation system of claim 7, wherein the
filtering section is disposed on the upstream side, along a
transportation direction, of the chamber.
9. The fluid transportation system of claim 7, wherein the
micropump transports fluid by repeatedly deforming the diaphragm;
and an acoustic capacitance of the pressure absorbing section has a
larger value than an acoustic capacitance of the chamber.
10. The fluid transportation system of claim 7, wherein at least
one wall surface of the pressure absorbing section comprises a thin
plate deformable by a fluid pressure; and a width of the thin plate
is larger than a width of the chamber.
11. The fluid transportation system of claim 7, wherein a flow path
resistance value of the filtering section is smaller than an
effective inner flow path resistance value of the micropump.
12. The fluid transportation system of claim 7, comprising a first
throttle flow path and a second throttle flow path at the both ends
of the chamber, of which respective flow path resistances change
corresponding to a differential pressure, wherein, a changing rate
of the flow path resistance of the first throttle flow path is
larger than that of the second throttle flow path; the actuator
transports fluid from the first throttle flow path toward the
second throttle flow path, by repeatedly increasing and decreasing
a pressure of fluid in the chamber in a first pattern where a time
of increasing the pressure is shorter than a time of decreasing the
pressure; and the actuator transports fluid from the second
throttle flow path toward the first throttle flow path, by
repeatedly increasing and decreasing the pressure of fluid in the
chamber in a second pattern where the time of increasing the
pressure is longer than the time of decreasing the pressure.
13. A fluid transportation system, comprising: a micropump provided
with a chamber and a diaphragm driven by an actuator; fluid
communication sections communicating with both ends of the chamber
of the micropump; a first pressure absorbing section that is
provided at one of the fluid communication sections so as to absorb
or reduce a fluid vibration pressure; a narrow section that is
provided at a position further than the first pressure absorbing
section from the chamber so as to narrow a flow path cross-section,
a second pressure absorbing section that is provided at another one
of the fluid communication sections so as to absorb or reduce a
fluid vibration pressure; a filtering section having a plurality of
micro flow paths, the filtering section being provided at a
position further than the second pressure absorbing section from
the chamber, wherein, when R represents a flow path resistance
value of the narrow section and C represents an acoustic
capacitance value of the first pressure absorbing section, a value
obtained by multiplication between R and C is not smaller than a
driving cycle period value of the micropump; and when R' represents
a flow path resistance value of the filtering section and C'
represents an acoustic capacitance value of the second pressure
absorbing section, a value obtained by multiplication between R'
and C' is not smaller than the driving cycle period value of the
micropump.
14. The fluid transportation system of claim 13, wherein the narrow
section is disposed on the downstream side, along a transportation
direction, of the chamber; and the filtering section is disposed on
the upstream side, along the transportation direction, of the
chamber.
15. The fluid transportation system of claim 13, wherein the
micropump transports fluid by repeatedly deforming the diaphragm;
and acoustic capacitances of the first and second pressure
absorbing sections have larger values than an acoustic capacitance
of the chamber.
16. The fluid transportation system of claim 13, wherein at least
one wall surface of each of the first and second pressure absorbing
sections comprises a thin plate deformable by a fluid pressure; and
a width of each thin plate is larger than a width of the
chamber.
17. The fluid transportation system of claim 13, wherein flow path
resistance values of the narrow section and the filtering section
are smaller than an effective inner flow path resistance value of
the micropump.
18. The fluid transportation system of claim 13, comprising a first
throttle flow path and a second throttle flow path at the both ends
of the chamber, of which respective flow path resistances change
corresponding to a differential pressure, wherein, a changing rate
of the flow path resistance of the first throttle flow path is
larger than that of the second throttle flow path; the actuator
transports fluid from the first throttle flow path toward the
second throttle flow path, by repeatedly increasing and decreasing
a pressure of fluid in the chamber in a first pattern where a time
of increasing the pressure is shorter than a time of the pressure;
and the actuator transports fluid from the second throttle flow
path toward the first throttle flow path, by repeatedly increasing
and decreasing the pressure of fluid in the chamber in a second
pattern where the time of increasing the pressure is longer than
the time of decreasing the pressure.
Description
[0001] This application is based on Japanese Patent Applications
No. 2005-253219 filed on Sep. 1, 2005 and No. 2006-157492 filed on
Jun. 6, 2006 in Japan Patent Office, the entire content of which is
hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a fluid transportation
system, and particularly relates to a fluid transportation system
that transports a tiny amount of fluid, using a micropump.
BACKGROUND OF THE INVENTION
[0003] In recent years, there have been developed and offered
various micropumps that are incorporated in a fluid transportation
system for biological tests, chemical analysis, drug discovery,
etc. and transport a tiny amount of liquid in high accuracy. Such a
micropump is structured such that a flow path and fluid reservoir
that communicate with a respective one of the both ends of a
chamber provided with a diaphragm driven by a piezoelectric
element, through a narrow flow path portion or open-and-close
valve.
[0004] Japanese Patent No. 3629405 discloses this type of a
micropump in which a diaphragm is driven by a piezoelectric element
and thus regularly deformed so as to transport fluid in one
direction through a chamber. However, this type of micropump has a
problem that a pressure vibration wave, which is generated in the
chamber due to driving of a piezoelectric element, is transferred
to the upstream side and downstream side through the inlet and
outlet.
[0005] In this situation, Japanese Patent No. 3569267 and Japanese
Non-examined Patent Publication No. 2000-265963 disclose providing
a pressure-absorbing section at the inlet and outlet so as to
absorb or reduce a vibration pressure. However, such a
pressure-absorbing section is not always complete, leaving a
problem that vibration that leaks from the pressure-absorbing
section affects sections where the vibration is applied in a case
where an active component such as a pump or movable valve is not
provided at the upstream side or downstream side of the
pressure-absorbing section.
[0006] With this background, an object of the present invention is
to provide a fluid transportation system capable of inhibiting a
vibration pressure generated in a chamber from leaking out from a
pressure absorbing section further to the upstream side and/or
downstream side.
SUMMARY OF THE INVENTION
[0007] In a first aspect of the invention, there is provided a
fluid transportation system, including:
[0008] a micropump provided with a chamber and a diaphragm driven
by an actuator;
[0009] fluid communication sections communicating with both ends of
the chamber of the micropump;
[0010] a pressure absorbing section that is provided at least one
of the fluid communication sections so as to absorb or reduce a
fluid vibration pressure; and
[0011] a narrow section that is provided at a position further than
the pressure absorbing section from the chamber so as to narrow a
flow path cross-section,
[0012] wherein,
[0013] when R represents a flow path resistance value of the narrow
section and C represents an acoustic capacitance value of the
pressure absorbing section, a value obtained by multiplication
between R and C is not smaller than a driving cycle period value of
the micropump.
[0014] In a second aspect of the invention, there is provided a
fluid transportation system, including:
[0015] a micropump provided with a chamber and a diaphragm driven
by an actuator;
[0016] fluid communication sections communicating with both ends of
the chamber of the micropump;
[0017] a pressure absorbing section that is provided at least one
of the fluid communication sections so as to absorb or reduce a
fluid vibration pressure; and
[0018] a filtering section having a plurality of micro flow paths,
the filtering section being provided at a position further than the
pressure absorbing section from the chamber,
[0019] wherein,
[0020] when R represents a flow path resistance value of the
filtering section and C represents an acoustic capacitance value of
the pressure absorbing section, a value obtained by multiplication
between R and C is not smaller than a driving cycle period value of
the micropump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIGS. 1A and 1B show a schematic structure of a fluid
transportation system in a first embodiment in accordance with the
invention, wherein (A) is a plan view of a thin etched plate and
(B) is a cross-sectional view;
[0022] FIGS. 2A to 2C are diagrams showing the operation (forward
liquid feeding) of a micropump of a fluid transportation system;
and
[0023] FIGS. 3A to 3C are diagrams showing (backward liquid
feeding) of the micropump;
[0024] FIG. 4 is a plan view showing a schematic structure of a
fluid transportation system in a second embodiment in accordance
with the invention;
[0025] FIG. 5 is a plan view showing a schematic structure of a
fluid transportation system in a third embodiment in accordance
with the invention;
[0026] FIG. 6 is a plan view showing a schematic structure of a
fluid transportation system in a fourth embodiment in accordance
with the invention;
[0027] FIG. 7 is a plan view showing a schematic structure of a
fluid transportation system in a fifth embodiment in accordance
with the invention;
[0028] FIG. 8 is a plan view showing a schematic structure of a
fluid transportation system in a sixth embodiment in accordance
with the invention;
[0029] FIG. 9 is a plan view showing a schematic structure of a
fluid transportation system in a seventh embodiment in accordance
with the invention;
[0030] FIG. 10 is a plan view showing a schematic structure of a
fluid transportation system in an eighth embodiment in accordance
with the invention;
[0031] FIG. 11 is a plan view showing a schematic structure of a
fluid transportation system in a ninth embodiment in accordance
with the invention.
PREFERRED EMBODIMENTS OF THE INVENTION
[0032] The invention includes the following structures.
(Item 1)
[0033] A fluid transportation system including:
[0034] a micropump provided with a chamber and a diaphragm driven
by an actuator;
[0035] fluid communication sections communicating with both ends of
the chamber of the micropump;
[0036] a pressure-absorbing section that is provided at least one
of the fluid communication sections so as to absorb or reduce a
fluid vibration pressure; and
[0037] a narrow section that is provided at a position further than
the pressure absorbing section from the chamber so as to narrow a
flow path cross-section,
[0038] wherein,
[0039] when R represents a flow path resistance value of the narrow
section and C represents an acoustic capacitance value of the
pressure absorbing section, a value obtained by multiplication
between R and C is not smaller than a driving cycle period value of
the micropump.
(Item 2)
[0040] A fluid transportation system including:
[0041] a micropump provided with a chamber and a diaphragm driven
by an actuator;
[0042] fluid communication sections communicating with both ends of
the chamber of the micropump;
[0043] a pressure-absorbing section that is provided at least one
of the fluid communication sections so as to absorb or reduce a
fluid vibration pressure; and
[0044] a filtering section having a plurality of micro flow paths,
the filtering section being provided at a position further than the
pressure absorbing section from the chamber,
[0045] wherein,
[0046] when R represents a flow path resistance value of the
filtering section and C represents an acoustic capacitance value of
the pressure absorbing section, a value obtained by multiplication
between R and C is not smaller than a driving cycle period value of
the micropump.
[0047] In the fluid transportation systems according to the above
Items 1 and 2, since a narrow section or a filtering section having
a plurality of micro flow paths that is provided at a position
further than the pressure absorbing section from the chamber, a
vibration pressure generated in the chamber by driving the actuator
is absorbed in two steps at the pressure absorbing section, and the
narrow section or filtering section. Thus, it is possible to
inhibit the vibration pressure generated in the chamber from
leaking out from the pressure absorbing section further to the
upstream side and downstream side.
[0048] Further, when R represents the flow path resistance value of
the narrow section or the filtering section, and C represents the
acoustic capacitance value of the pressure absorbing section, the
value obtained by multiplication between R and C is preferably
larger than or equal to a driving cycle period value of the
micropump. Thus, after a vibration of the pressure absorbing
section ceases, a subsequent vibration is started by the actuator,
and thereby fluid is smoothly transported. Herein, in order that
the value obtained by multiplication between R and C does not
become too large, the flow path resistance value of the narrow
section or the filtering section is smaller than the effective
inner flow path resistance value of the micropump.
[0049] Particularly, in the fluid transportation system of Item 2,
the filtering section eliminates foreign matters having been mixed
in the fluid. Accordingly, the filtering section is preferably
disposed on upstream side, in the transportation direction, of the
chamber.
[0050] In the fluid transportation system of Items 1 and 2, since
the vibration pressure is effectively absorbed, the value of the
acoustic capacitance of the pressure absorbing section is
preferably larger than that of the acoustic capacitance of the
chamber. In order to obtain the same effect, preferably, at least
one wall surface of the pressure absorbing section is a thin plate
deformable by a fluid pressure and the width of the thin plate is
larger than the width of the chamber.
[0051] Further, it is possible to achieve fluid transportation in
high accuracy by the use of a micropump that includes a first
throttle flow path and a second throttle flow path at the both ends
of the chamber of which respective flow path resistances change
corresponding to a differential pressure, wherein the changing rate
of the flow path resistance of the first throttle flow path is
larger than that of the second throttle flow path; the actuator
transport fluid from the first throttle flow path toward the second
flow path, by repeatedly increasing and decreasing the pressure of
fluid in the chamber in a first pattern where the time of
increasing the pressure is shorter than the time of decreasing the
pressure; and the actuator transports fluid from the second
throttle flow path toward the first flow path, by repeatedly
increasing and decreasing the pressure of fluid in the chamber in a
second pattern where the time of increasing the pressure is longer
than the time of decreasing the pressure.
[0052] Now, an embodiment of a fluid transportation system in
accordance with the invention will be described, referring to the
attached drawings. Herein, common symbols are given to the same
members and components common in the figures showing the respective
embodiments, and overlapping descriptions are omitted.
(Schematic structure in a first embodiment, referring to FIGS. 1A
and 1B)
[0053] A fluid transportation system 10A in accordance with a first
embodiment includes, as shown in FIG. 1B, a joint of a glass
substrate 11 and thin plate 20. The glass substrate 11 is formed
with an inlet 12 and outlet 13. Further, the thin plate 20 is made
of a SI-based substrate that is formed by etching with a chamber
21, throttle flow paths 22 and 23, fluid reservoir 24, filtering
section 25, flow path 26, pressure absorbing section 27, and narrow
section 28, these communicating with each other. Further, a
piezoelectric element 30 as an actuator is stuck on the outer
surface of the chamber 21, and the membrane portion of the chamber
21 functions as a diaphragm.
[0054] Taking an example of concrete dimensions, the thin plate 20
is 200 .mu.m thick; the membrane diaphragm or the like of the
chamber 21 is 30 .mu.m thick; and the throttle flow paths 22 and 23
are 25 .mu.m deep.
[0055] The fluid reservoir 24 is formed with a larger width and
capacity than the chamber 21 and functions as the pressure
absorbing section on the inlet side. The filtering section 25
includes a coarser first filtering section 25a and a finer second
filter 25b, and is located at a position further than the chamber
21 from the fluid reservoir 24. Further, one end of the fluid
reservoir 24 communicates with the inlet 12 of the glass substrate
11 through the filtering section 25.
[0056] One end of the narrow section 28 communicates with the
pressure absorbing section 27 and is located at a position further
from the chamber 21, narrowing the flow path cross-section, while
the other end communicates with the outlet 13 of the glass
substrate 11. The absorbing section 27 is formed with a larger
width and capacity than the chamber 21.
(Operation of micropump, referring to FIGS. 2A to 2C and 3A to
3C)
[0057] In the fluid transportation system 10A, the micropump 31
includes the chamber 21, throttle flow paths 22 and 23, and
piezoelectric element 30. Now, the operation of the micropump 31
will be described.
[0058] Conceptually, the micropump 31 includes throttle flow paths
22 and 33 at the both ends of the chamber 21 of which respective
flow path resistances change corresponding to a differential
pressure, wherein, the changing rate of the flow path resistance of
the throttle flow path 22 is larger than that of the throttle flow
path 23; fluid is transported from the throttle flow path 22 toward
the throttle flow path 23, by repeatedly increasing and decreasing
a pressure of fluid in the chamber by the piezoelectric element 30
in a first pattern where the time of increasing the pressure is
shorter than the time of decreasing the pressure (refer to FIGS. 2A
to 2C); and fluid is transported from the throttle flow path 23
toward the throttle flow path 22, by repeatedly increasing and
decreasing the pressure of fluid in the chamber by the
piezoelectric element 30 in a second pattern where the time of
increasing the pressure is longer than the time of decreasing the
pressure (backward liquid feeding, refer to FIGS. 3A to 3C).
[0059] Concretely, FIGS. 2A to 2C show the liquid feeding state in
the forward direction (the first pattern), wherein when a voltage
in the wave form shown in FIG. 2A is applied to the piezoelectric
element 30 to quickly increase the pressure of fluid in the chamber
21, a turbulent flow occurs and the flow path resistance becomes
larger in the throttle flow path 22, and thus the fluid is
exhausted from the chamber 21 through the throttle flow path 23.
When the pressure of fluid in the chamber 21 is slowly decreased,
fluid is introduced into the chamber 21 through the throttle flow
path 22 with a small flow path resistance. In the present first
embodiment and also in other embodiments, description will be given
with an assumption that fluid is transported in the first
pattern.
[0060] FIGS. 3A to 3C show the liquid feeding state in the backward
direction (the second pattern), wherein when a voltage in the wave
form shown in FIG. 3A is applied to the piezoelectric element 30 to
slowly increase the pressure of fluid in the chamber 21, fluid is
exhausted from the chamber 21 through the throttle flow path 22
with a small flow path resistance. When the pressure of fluid in
the chamber 21 is quickly decreased, a turbulent flow occurs in the
throttle flow path 22 to increase the flow path resistance, and
thus fluid is introduced into the chamber 21 through the throttle
flow path 23.
(Function of Filtering Section and Narrow Section)
[0061] When the micropump 31 is driven in the first pattern, fluid
is transported with high accuracy to the outlet 13 through the
inlet 12, filtering section 25, fluid reservoir 24, throttle flow
path 22, chamber 21, throttle flow path 23, flow path 26, pressure
absorbing section 27, and narrow section 28.
[0062] In the transportation process described above, by driving
the piezoelectric element 30, a pressure vibration wave generated
in the chamber 21 is transmitted to the inlet and outlet sides
through fluid. The fluid reservoir 24 and pressure absorbing
section 27 absorb or reduce the vibration pressure, by the
elasticity of the membrane portion thereof, and prevents the
vibration pressure from being transmitted to the inlet and outlet
sides. However, it is impossible to completely absorb transmission
of the vibration pressure.
[0063] With regard to the fluid reservoir, region Y (refer to FIG.
1A) excluding the region formed with the filtering section 25
functions as a pressure absorbing section.
[0064] Since the filtering section 25 and narrow section 28 have a
large flow path resistance, a remaining vibration pressure having
not been absorbed by the fluid reservoir 24 nor the pressure
absorbing section 27 can be absorbed substantially completely,
which prevents the vibration pressure from leaking from the inlet
12 and outlet 13 to the upstream and downstream sides.
Particularly, the filtering section 25 can eliminate foreign
matters mixed in the fluid.
(Schematic Structure in a Second Embodiment, Refer to FIG. 4)
[0065] A fluid transportation system 10B in a second embodiment is
constructed basically, as show in FIG. 4, by connecting, in
parallel, two fluid transportation systems each including a
micropump 31, described in the first embodiment, and merges
transported fluids at a merging section 29a which joints flow paths
29, 29 provided on the downstream side of narrow sections 28,
28.
[0066] When plural micropumps fluid-communicate with each other
through a flow path, a vibration generated by one micropump affects
the operation of another micropump and tends to cause
characteristic variation. However, as in the present second
embodiment, when micropumps 31, 31 are connected in parallel,
micropumps 31, 31 do not affect each other.
(Schematic Structure in a Third Embodiment, Refer to FIG. 5)
[0067] A fluid transportation system 10C in a third embodiment is
constructed, as shown in FIG. 5, basically by connecting, in
parallel, two fluid transportation systems each including a
micropump 31, similarly to the second embodiment, and merges
transported fluids at a merging section 29a which joints flow paths
29, 29 communicating with the downstream side of pressure absorbing
sections 27. In the present third embodiment, instead of the narrow
section 28 described in the first and second embodiment, filtering
sections 25 (each including a first filtering section 25a and
second filtering section 25b) are provided. Herein, the downstream
side of the fluid reservoirs 24 and the upstream side of the
pressure absorbing sections 27 have a circular shape in a top
view.
[0068] The effects of the present third embodiment are the same as
those in the first embodiment, and the effects by the parallel
connection of the two micropumps 31 are the same as in the second
embodiment.
(Schematic Structure of a Fourth Embodiment, Refer to FIG. 6)
[0069] A fluid transportation system 10D in a fourth embodiment
has, as shown in FIG. 6, the same basic structure as in the first
embodiment, and further includes a flow path 41 on the upstream
side of the filtering section 25 and a flow path 42 on the
downstream side of the narrow section 28.
(Schematic Structure of a Fifth Embodiment, Refer to FIG. 7)
[0070] A fluid transportation system 10E in a fifth embodiment has,
as shown in FIG. 7, is provided with a filtering section 25
(including a first filtering section 25a and second filtering
section 25b) in the pressure absorbing section 27 instead of a
narrow flow path 28, other structures being the same as in the
first embodiment).
[0071] The effects of the present fifth embodiment are the same as
in the first embodiment, and further it is possible to prevent
foreign matters from mixing into the chamber 21 by the filtering
section 25. Particularly, it is effective when an actuator capable
of transporting fluid in both directions, with an example of a
micropump 31.
(Schematic Structure of a Sixth Embodiment, Refer to FIG. 8)
[0072] A fluid transportation system 10F in a sixth embodiment is,
as shown in FIG. 8, the structure on the upstream side is the same
as in the first embodiment, while a throttle flow path 23, flow
path 26, and outlet 13 are provided on the downstream side of the
micropump 31, wherein the pressure absorbing section 27, shown in
the first embodiment, is omitted.
[0073] In the sixth embodiment, the flow path 26 on the downstream
side is sufficiently long, and reaches the outlet 13 (atmospheric
air opening) without communicating with another micropump. Such a
structure is used for a purpose, for example, of exhausting waste
liquid remaining on the upstream side than the inlet 12 to a
separated place. With regard to the downstream side, since the
system is affected little by a pressure vibration, it is necessary
to provide a pressure absorbing section (fluid reservoir 24) and
filtering section 25 only on the upstream side. Thus, a small sized
fluid transportation system 10F can be achieved with a simple
structure.
(Schematic Structure of a Seventh Embodiment, Refer to FIG. 9)
[0074] A fluid transportation system 10G in a seventh embodiment
has, as shown in FIG. 9, the same structure on the upstream side of
a micropump 31 as in the first embodiment, and is provided with a
throttle flow path 23, flow path 26, pressure absorbing section 27,
and outlet 13 on the downstream side of the micropump 31, wherein
the narrow section 28, described in the first embodiment, is
omitted.
[0075] In the present seventh embodiment, a filtering section 25 is
provided only on the upstream side which is affected much by a
pressure vibration, and the narrow section 28 on the downstream
side is omitted for a smaller size.
(Schematic Structure of an Eighth Embodiment, Refer to FIG. 10)
[0076] In a fluid transportation system 10H in an eight embodiment,
as shown in FIG. 10, the flow path described in the first
embodiment is omitted, and a narrow section 28 communicates with an
outlet 13. Other structures are the same as in the first
embodiment. It is also possible to achieve a small size by omitting
a flow path 26.
(Schematic Structure of a Ninth Embodiment, Refer to FIG. 11)
[0077] In a fluid transportation system 10I in a ninth embodiment
is structured, as shown in FIG. 11, the upstream side of a
micropump 31 is constructed, same as the downstream side, with a
pressure absorbing section 27 and a narrow section 28, wherein an
inlet 12 is provided on the upstream side of the narrow section 28.
In the case of a transportation system into which foreign matters
hardly be mixed, for example, in the case of a transportation
system in a sealed state isolated from outside, since trapping of
foreign matters by a filtering section 25 is unnecessary, it is not
necessary to provide a filtering section 25 on the upstream side of
the micropump 31. As a filtering section 25 is omitted, the
manufacturing process of a fluid transportation system 10I is
simplified.
(Absorption Vibration Pressure)
[0078] Now, absorption of the vibration pressure due to pulsation
of the micropump 31 will be described in detail. In order to absorb
the vibration pressure, it is necessary to take the acoustic
capacitance into account. The acoustic capacitance corresponds to
the compression (or deformation) volume for a unit pressure. With
regard to the acoustic capacitances of the chamber 21, fluid
reservoir 24, and pressure absorbing section 27, deformation of the
glass substrate 11 can be neglected, and the acoustic capacitances
can be calculated by just obtaining the deformed volumes of the
membrane portions at the time of applying a unit pressure to inside
the chamber 21, fluid reservoir 24, and pressure absorbing section
27 respectively.
[0079] With regard to the acoustic capacitances of fluid in the
chamber 21, fluid reservoir 24, and pressure absorbing section 27,
the acoustic capacitances can be calculated from the decrease in
volume at the time of applying a unit pressure to the entire inside
fluid. Alternatively, the acoustic capacitances can also be
obtained from the density of fluid, the acoustic velocity in the
fluid, and the inner volumes of the chamber 21, fluid reservoir 24,
and pressure absorbing section 27.
[0080] An acoustic capacitance has two components. They are a
component of deformation, caused by a pressure, of a part of a
housing which stores fluid inside, and a component of compression,
caused by a pressure, of the fluid itself inside the housing. The
value of an acoustic capacitance in a practical fluid
transportation system is to be determined with the sum of these two
components. However, as in the case of the first embodiment, if the
former component is larger than the latter component by several
orders, sometimes, only the former component is practically taken
into account.
[0081] In the fluid transportation system, the acoustic
capacitances of the fluid reservoir 24 (concretely, region Y) and
the pressure absorbing section 27 are preferably larger than that
of the chamber 21. It is possible to effectively absorb the
vibration pressure in the chamber caused by driving the micropump
31 (piezoelectric element 30).
[0082] In order to make the acoustic capacitances of the fluid
reservoir 24 and pressure absorbing section 27, the reservoir 24
and pressure absorbing section 27 are preferably formed of a
membrane section. Concretely, in the first embodiment, the
reservoir 24 and pressure absorbing section 27 are formed of a
membrane section which is obtained by etching a thin plate (for
example, a membrane with a thickness of approximately 30 .mu.m
obtained by etching a thin plate with a thickness of 200 .mu.m by
about 170 .mu.m) to have a width larger than that of the chamber
21.
[0083] Taking an example of dimensions, region Y in the fluid
reservoir 24 and the pressure absorbing section 27 have
approximately the same dimension, that is, a width of 1.5 mm and a
length of 3.0 mm. The both acoustic capacitances of these are
approximately 90.times.10.sup.-18 (m.sup.3/Pa).
[0084] Taking an example of the dimensions of the filtering section
25, the first filtering section 25a is constructed with 10 micro
grooves with an opening width of 40 .mu.m, length of 200 .mu.m, and
depth of 25 .mu.m. The second filtering section 25b is constructed
with 17 micro grooves with an opening width of 20 .mu.m, length of
60 .mu.m, and depth of 25 .mu.m.
[0085] The filtering section 25 has a role to prevent entrance of
foreign matters into the chamber 21, and has a function to damp a
pressure vibration because of a high flow path resistance value R
as well as the narrow section 28. A liquid with a viscosity of 1 cp
(corresponding to water at 20.degree. C.) has a resistance value R
of approximately 2.0.times.10.sup.12 (Ns/m.sup.5).
[0086] If the filtering section 25 is arranged to have these
functions, just in case that a part of the filtering section 25 is
clogged with foreign matters, fluid can flow to the rest of the
filtering section, which gives an advantage of a structure with a
higher security compared to the case where only a single narrow
section 28 is disposed.
[0087] Taking an example of the dimensions of the narrow section
28, the opening width is 40 .mu.m, length is 0.50 mm, and depth is
170 .mu.m. A liquid with a viscosity of 1 cp has a resistance value
R of approximately 1.2.times.10.sup.12 (Ns/m.sup.5).
[0088] In such a manner, by making the opening cross-sectional area
of the narrow section 28 sufficiently smaller (not greater than a
half, and preferably not greater than 1/10) than the
cross-sectional area of the flow path before and after the narrow
section 28, a required flow path resistance value R can be secured
even if the flow path is comparatively short.
[0089] Further, by making the narrow section 28 sufficiently
narrow, substantially no pressure distribution and no velocity
distribution of the fluid inside the narrow section 28 are
generated. Therefore, stable pressure damping characteristics can
always be obtained, independently from the driving voltage wave
form, frequency, or disturbance conditions.
[0090] Herein, the filtering section 25 or narrow section 28 is
preferably disposed adjacent to the pressure absorbing section
(including the fluid reservoir 24 and pressure absorbing section
27). Thus, it can be avoided that the characteristics become
unstable in such a way that a vibration wave having not been
absorbed by the pressure absorbing section interferes between the
pressure absorbing section and the filtering section 25 or between
the pressure absorbing section and the narrow section 28.
[0091] On the other hand, on the upstream side of the chamber 21,
it is preferable to provide a filtering section 25. Thus, when a
foreign matter comes flowing from the upstream side, it is
prevented that the foreign matter is mixed into the chamber 21.
[0092] On the downstream side of the chamber 21, it is preferable
to provide not a filtering section 25 but a narrow section 28.
Thus, just in the case that a foreign matter is mixed into the
chamber 21, the foreign matter is expected to flow out to the
downstream side. In this case, the cross-sectional area of the
narrow section 28 is preferably larger than the cross-sectional
area of a stitch of the filtering section 25.
[0093] Further, in the fluid transportation system, when R
represents the flow path resistance value of the narrow section 28
or the filtering section 25, and C represents the acoustic
capacitance value of the fluid reservoir 24 or the pressure
absorbing section 27, the value obtained by multiplication between
R and C is preferably not smaller than a driving cycle period value
of the micropump 31 (piezoelectric element 30). Thus, after the
vibration of the fluid reservoir 24 or the pressure absorbing
section 27 ceases, a subsequent vibration is started by the
piezoelectric element, and thereby fluid is smoothly transported.
Herein, if the value obtained by multiplication between R and C is
too large, the response after a start of driving the micropump 31
becomes low, and it is too long before a desired flow velocity is
attained, which is not preferable. Accordingly, the value of
obtained by multiplication between R and C is preferably set to be
not longer than a preferable response time in a practical
embodiment.
[0094] In a case of a structure, for example, as in the second
embodiment shown in FIG. 4, that has two micropumps 31, 31 in the
same shape and disposed in parallel and merges liquids having been
respectively transported at the merging section 29a, if the timing
when the liquids fed out from the respective micropumps 31, 31
reach the merging section 29a deviates, problems occurs, for
example, gas bubbles collect in the merging section 29a.
[0095] Accordingly, deviation of the reach timing of the liquids
transported from the micro pumps 31, 31 is permitted only for a
time not longer than the time for transportation of liquid from one
micropump 31 for the amount to fill the inner volume of the merging
section 29a (the region shown by dashed lines). In the case of the
second embodiment, since the merging section 29a is 200 .mu.m wide
and the flow rate by the micropumps 31, 31 is approximately 400
nL/sec, deviation of the reach timing is permitted only for about
20 milli sec. Therefore, the upper limit value obtained by
multiplication between R and C in the second embodiment is needed
to be set to about 20 milli sec. Further, taking into account that
it is after a time which is about three times the time constant
when the transportation speed becomes stable, the upper limit value
obtained by multiplication between R and C is preferably about 6
milli sec which is approximately 1/3 of the above described
value.
[0096] Herein, the flow path resistance value R corresponds to the
coefficient of pressure loss at the time when fluid flows in the
flow path, and can be obtained by R=.DELTA.P/Q, Q representing the
flow rate per unit time and .DELTA.P representing the pressure
loss.
[0097] Setting the resistance value R too large is not preferable
because the flow of liquid transported by the micropump 31 is
inhibited and the flow velocity is lowered. Accordingly, the
resistance value R of the filtering section 25 or the narrow
section 28 is preferably smaller than the effective inner flow path
resistance value of the micropump 31.
[0098] The micropump 31 in the first embodiment achieves preferable
pump characteristics (The flow rate and generation pressure are
high.) with the driving cycle period in the vicinity of 90 .mu.sec.
On the other hand, the value obtained by multiplication between R
and C at the portion of the fluid reservoir 24 and the adjacent
filtering section 25 is 180 .mu.sec, and the value obtained by
multiplication between R and C at the portion of the pressure
absorbing section 27 and the adjacent narrow section 28 is 108
.mu.sec. Since these values obtained by multiplication between R
and C are greater than the driving cycle period (90 .mu.sec) of the
micropump 31, transportation of liquid becomes smooth by the above
described effect, and characteristics variation becomes
smaller.
[0099] As an example, as the second embodiment shown in FIG. 4,
with a structure in which a pair of transportation systems, in the
same shape, including the respective micropumps 31, 31 were
disposed in parallel and liquids having been respectively
transported were merged in a merging section 29a, the respective
liquid feeding amounts were measured. The two liquids were colored
with respective dyes; the flow rate ratio between the two liquids
was determined by the ratio between the widths of the laminar flows
of the two liquids on the downstream side of the merging section
29a; and the total flow rate of the two liquids at a velocity at
which the meniscus on the downstream side of the merging section
29a moves was measured. In the case where no narrow section 28 was
provided, the variation in the liquid feeding amounts of the two
liquids was approximately .+-.20%, wherein the liquid feeding ratio
varied each time of liquid feeding. However, by providing narrow
sections 28, the variation in the liquid feeding amounts of the two
liquids was lowered approximately to +5% or lower, and the results
stopped varying each time of liquid feeding.
[0100] On the other hand, when the length of the narrow sections 28
were changed from 0.50 mm to 0.35 mm, the variation in the liquid
feeding amounts of the two liquids increased approximately to
.+-.10%. Herein, the resistance value R of the narrow sections 28
was approximately 0.8.times.10.sup.12 (Ns/m.sup.5) and the value
obtained by multiplication between R and C was 72 .mu.sec, which is
a smaller value than the driving cycle period (90 .mu.sec) of the
micropumps 31. From this point, it is understood that the effect of
the narrow sections 28 is little, and the effect becomes
significant when the value obtained by multiplication between R and
C becomes the driving cycle period or larger.
[0101] As another example, as the third embodiment shown in FIG. 5,
with a structure in which a pair of transportation systems, in the
same shape, including the respective micropumps 31, 31 were
disposed in parallel, liquids having been respectively transported
were merged in a merging section 29a, and filtering sections 25
were provided at the pressure absorbing sections 27, the respective
liquid feeding amounts were measured in the same manner as
described above.
[0102] The micropumps 31, 31 used here had a driving cycle period
of 250 .mu.sec. The two filtering sections 25 on the downstream
side have the same shape and dimensions. The first filtering
sections 25a have a structure having 9 micro grooves with an
opening width of 130 .mu.m, length of 450 .mu.m, and depth of 80
.mu.m. The second filtering sections 25b have a structure having 20
microgrooves with an opening width of 60 .mu.m, length of 180
.mu.m, and depth of 80 .mu.m. A liquid with a viscosity of 1.5 cp
has a resistance value R of approximately 0.18.times.10.sup.12
(Ns/m.sup.5). The two pressure absorbing sections 27 has the same
shape and dimensions, wherein the upstream side is in a
substantially circular shape with a diameter of 5.6 mm, and the
values of the acoustic capacitances C are both approximately
1700.times.10.sup.-18 (m.sup.3/Pa). A test of feeding liquid by
merging the two liquids in these conditions was performed,
resulting in the variation in the liquid feeding amounts of
approximately .+-.3% or lower.
[0103] On the other hand, as a result of comparison tests for a
case where the length of the respective filtering sections 25 was
shortened to be approximately 0.7 times the above described value,
and for a case where filtering sections 25 were not provided,
variation in the respective liquid feeding amounts was
approximately .+-.10% in the former case, and .+-.20% in the latter
case. With these tests also, it proved that the effects become
significant when the value obtained by multiplication between R and
C is larger or equal to the driving frequency of the micropumps
31.
[0104] Now, the cause of the significant effects obtained with the
value obtained by multiplication between R and C larger than the
value of the driving frequency of the micropumps 31 will be
described. If a driving voltage in a pulse form is applied to the
micropumps 31 by adding one pulse to generate a differential
pressure, the value of the generated differential pressure is
represented by P.sub.0, and the value of the differential pressure
after an elapsed time of t from the generation of the differential
pressure is represented by P(t), then the relation is
P(t)=P.sub.0exp(-t/RC). This drop in the differential pressure is
caused by a flow of liquid in a narrow section 28 or a filtering
section 25. When Q(t) represents the flow rate of a liquid flowing
in the narrow section 28 or filtering section 25 after the elapsed
time of t, Q(t) is expressed by Q(t)=P.sub.0exp(-t/RC)/R.
[0105] As understood from the above expression, even if a momentary
differential pressure is generated by a driving voltage in a pulse
form, a time delay is caused on the flow of the liquid in a narrow
section 28 or filtering section 25, and the liquid does not flow
until a certain time elapses. In other words, even if the
differential pressure P generated by driving the micropump 31
changes suddenly, in respect of the flow rate Q of the liquid
flowing in the narrow section 28 or filtering section 25, the
liquid tends to flow gradually, taking an elapse time t, at
shortest, exceeding the value obtained by multiplication between R
and C.
[0106] Accordingly, since the change in the flow rate Q cannot
sufficiently follow a phenomenon that sequentially changes in a
shorter time than the value obtained by multiplication between R
and C, as a result, a fluid vibration with a period shorter than
the value obtained by multiplication between R and C is damped
without a leakage to outside the narrow section 28 or filtering
section 25, which realizes stable liquid feeding with a steady flow
almost free from superimposed pulsating vibrations.
[0107] Further, the fluid reservoir 24 or the pressure absorbing
section 27 preferably not only have a function to absorb or reduce
vibration pressure, but also have a characteristic to reflect a
compressional pressure wave of a high frequency wave. By reflecting
the high frequency component to the side of chamber 21, the high
frequency component is inhibited from being transmitted to either
the inlet side or outlet side, which allows the flow of the fluid
to be smooth and free from pulsation.
(Other Embodiments)
[0108] A fluid transportation system in accordance with the
invention is not limited to the above described embodiment, and can
be variously changed without departing from the spirit of the
invention.
[0109] For example, a fluid transportation system may be
constructed with a glass substrate 11 formed with structures
including the chamber 21, throttle flow paths 22 and 23, fluid
reservoir 24, and pressure absorbing section 27. The flow path 26
may be a plurality of flow paths disposed in parallel between the
throttle flow path 23 and pressure absorbing section 27.
[0110] Still further, active valves may be provided facing the
throttle flow paths disposed at the both ends of the chamber 21.
For this kind of an active valve, a piezoelectric element is
provided at a membrane portion facing a throttle flow path and
driven so as to transport fluid in one direction by forcefully
opening and closing the throttle flow path. Even when active valves
are provided, a time lag with respect to increasing and decreasing
the pressure occurs between the active valves and the chamber 21,
which transmits the vibration pressure toward outside the chamber
21. Therefore, as in the present embodiment, it is advantageous to
provide a fluid reservoir 24 and pressure absorbing section 27, and
provide a filtering section 25 and narrow section 28 so as to
prevent the vibration pressure from leaking outside.
[0111] Either a filtering section 25 or narrow section 28 is
preferably disposed at both the upstream side and downstream side
of a micropump 31 so that vibration transmission is completely
isolated from outside. Herein, any one of a combination of
filtering sections 25, a combination of a filtering section 25 and
a narrow section 28, and a combination of narrow sections 28 can be
applied. In a case where either the upstream side or downstream
side is affected little by vibration, and particularly in such a
case where the flow path 26 communicates with an outlet 13
(atmospheric air opening) without fluid-communication with another
micropump, as in the sixth embodiment (refer to FIG. 8), the narrow
section 28 or filtering section 25 may be omitted on the downstream
side of the micropump 31. Likewise, the pressure absorbing section
27 or fluid reservoir 24 is not always needed to be disposed on
both the upstream side and downstream side of the micro pump 31,
and may be disposed on only one of the upstream side and downstream
side.
* * * * *