U.S. patent application number 10/566580 was filed with the patent office on 2007-03-22 for diaphragm pump and cooling system with the diaphragm pump.
Invention is credited to Sakae Kitajo, Atsushi Ochi, Yasuhiro Sasaki, Mitsuru Yamamoto.
Application Number | 20070065308 10/566580 |
Document ID | / |
Family ID | 34113910 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070065308 |
Kind Code |
A1 |
Yamamoto; Mitsuru ; et
al. |
March 22, 2007 |
Diaphragm pump and cooling system with the diaphragm pump
Abstract
A diaphragm pump enabling an increase in pump efficiency by
reducing the pressure loss of liquid and reduction in thickness.
The flow passage in piezoelectric pump (1) includes a pressure
chamber (50) formed into a flat shape in cross section and a
suction side flow passage (70a) and discharge side flow passage
(70b). The suction side flow passage (70a) and the discharge side
flow passage (70b) are disposed at both ends of the pressure
chamber (50) so that the axes thereof are aligned with each other.
The check valves (20a, 20b) are respectively disposed on the
suction side flow passage (70a) and the discharge side flow passage
(70b), and are tilted relative to the flow direction of the
liquid.
Inventors: |
Yamamoto; Mitsuru;
(Minato-ku, JP) ; Sasaki; Yasuhiro; (Minato-ku,
JP) ; Ochi; Atsushi; (MInato-ku, JP) ; Kitajo;
Sakae; (Minato-ku, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
34113910 |
Appl. No.: |
10/566580 |
Filed: |
July 21, 2004 |
PCT Filed: |
July 21, 2004 |
PCT NO: |
PCT/JP04/10339 |
371 Date: |
January 31, 2006 |
Current U.S.
Class: |
417/413.1 |
Current CPC
Class: |
F04B 43/046
20130101 |
Class at
Publication: |
417/413.1 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 2003 |
JP |
2003-285915 |
Claims
1. A diaphragm pump comprising: a pressure chamber formed into a
flat shape and is filled up with liquid; a suction side flow
passage and a discharge side flow passage disposed at both ends of
the pressure chamber so that axes thereof are aligned with each
other and are connected with the pressure chamber; at least one
groove formed in a peripheral wall of the pressure chamber and for
accelerating a flow of the liquid downstream in a flow direction;
and at least one diaphragm disposed on at least one of an upper
surface and a lower surface of the pressure chamber and for
oscillation to make a volume of the pressure chamber variable.
2. The diaphragm pump according to claim 1, wherein the groove has
a part with an opening in the upper surface facing the pressure
chamber, into which the liquid flows, and a side part with an
opening opened to a peripheral wall surface of the pressure
chamber, from which the liquid is discharged downstream in the flow
direction.
3. The diaphragm pump according to claim 1 or 2, wherein the groove
is extended in a radial direction while a point in the vicinity of
an entrance of the discharge side flow passage is set as the
center.
4. The diaphragm pump according to any one of claims 1 or 2,
wherein the axes are positioned at the center of a cross-sectional
shape of the pressure chamber in a surface orthogonal to the
axes.
5. The diaphragm pump according to any one of claims 1 or 2,
wherein each cross-sectional shape of the pressure chamber, the
suction side flow passage, and the discharge side flow passage in a
surface orthogonal to the axes are formed in an approximate
rectangle.
6. The diaphragm pump according to claim 5, wherein a lower surface
of the pressure chamber and the lower surfaces of the suction side
flow passage and the discharge side flow passage are formed on the
same surface.
7. The diaphragm pump according to any one of claims 1, 2 or 6,
wherein a length of the pressure chamber viewed from an upper
surface in a direction orthogonal to the axes is continuously
shortened toward the suction side flow passage or the discharge
side flow passage.
8. The diaphragm pump according to any one of claims 1, 2 or 6,
wherein a height of the pressure chamber is continuously lowered
toward the suction side flow passage or the discharge side flow
passage.
9. The diaphragm pump according to any one of claims 1, 2 or 6,
further comprising: check valves, respectively disposed on the
suction side flow passage and the discharge side flow passage, at
least one of the check valves being tilted relative to a direction
of the axes.
10. The diaphragm pump according to any one of through 9 claims 1,
2 or 6, further comprising: at least one intake opened to an upper
surface of the suction side flow passage and to introduce bubbles
mixed in the liquid; and a sealed space connected with the intake
and to collect the introduced bubbles.
11. The diaphragm pump according to claim 10, wherein the intake is
positioned in the suction side flow passage upstream relative to
the check valve.
12. The diaphragm pump according to any one of claims 1, 2, 6 or
11, wherein the diaphragm is a piezoelectric oscillator driven by a
piezoelectric element.
13. A cooling system comprising: the diaphragm pump according to
any one of claims 1, 2, 6 or 11; and a closed-structure flow
passage for circulating liquid discharged from the discharge side
flow passage in the diaphragm pump and for returning the liquid to
the suction side flow passage.
Description
TECHNICAL FIELD
[0001] The present invention relates to a diaphragm pump used for a
cooling system or the like, and in particular, relates to a slim
diaphragm pump capable of discharging liquid efficiently. Further,
the present invention relates to a cooling system with the
diaphragm pump used for cooling electronic equipment or the
like.
BACKGROUND ART
[0002] As the performance of electronic equipment becomes higher
and processing speed is enhanced, power consumption for electronic
parts such as CPU increases. As a result, the heating value in the
electronic parts becomes high, and it is absolutely necessary to
have a technology that can efficiently dissipate heat generated
from the electronic parts and that remains inside the electronic
equipment in terms of ensuring reliable operation of the electronic
equipment.
[0003] As a cooling technique for a portable personal computer such
as a notebook personal computer, instead of an air-cooled cooing
system, there is proposed a water-cooled cooling system that can
provide cooling by circulating liquid by a pump (for example, refer
to Japanese Patent Laid-Open No. 2002-232174). The water-cooled
cooling system is provided with a closed-structure flow passage to
be in thermally contact with heating parts, such as electronic
parts, and a pump to circulate the liquid inside the flow passage.
The cooling system dissipates heat by circulating the liquid that
is heated by the heated parts with the pump, so as to provide
cooling for the heated parts.
[0004] As the pump for the cooling system, a piezoelectric pump, a
kind of diaphragm pump, which is compact and capable of generating
a high discharge pressure, is often used. The piezoelectric pump is
usually provided with a pressure chamber with a suction port and a
discharge port, a piezoelectric oscillator disposed on a wall of
the pressure chamber, and a flow passage that is connected with the
suction port and the discharge port. In the piezoelectric pump, the
piezoelectric oscillator functions as a diaphragm in the diaphragm
pump. The piezoelectric oscillator is provided with an elastic
plate made of metal and the like and a piezoelectric element bonded
to the elastic plate. When a voltage is applied to the
piezoelectric element, the elastic plate (piezoelectric oscillator
itself) is bent and displaced. In the piezoelectric pump, by
oscillating the piezoelectric oscillator, pressure operating on the
liquid is generated in the pressure chamber. Further, the suction
port and the discharge port are provided with check valves to
prevent backflow of the liquid so as to restrict the flow direction
of the liquid from the suction port to the discharge port.
[0005] FIG. 10 shows an example of a conventional piezoelectric
pump. The piezoelectric pump shown in FIG. 10 is provided with
piezoelectric oscillator 130 arranged to form an upper surface of
pressure chamber 150. On the lower surface of pressure chamber 150,
suction port 121a is provided for ingesting the liquid and
discharge port 121 b is provided for discharging the liquid.
Suction side flow passage 170a for supplying the liquid to suction
port 121a is formed under pressure chamber 150, and is connected
with suction port 121a. Discharge side flow passage 170b, a flow
passage for the liquid discharged from discharge port 121b, is
formed under the pressure chamber 150, and is connected with
discharge port 121b. With this arrangement, the flow passage of the
liquid in piezoelectric pump 100 is formed from suction side flow
passage 170a to discharge side flow passage 170b through suction
port 121a, pressure chamber 150, and discharge port 121b in
order.
[0006] Suction port 121a and discharge port 121b are respectively
provided with suction valve 120a and discharge valve 120b. Suction
valve 120a and discharge valve 120b are made from elastic members,
such as silicon rubber, and respectively control the opening and
closing of suction port 121 a and discharge port 121b.
[0007] Piezoelectric pump 100, arranged as described above,
operates as follows. When piezoelectric oscillator 130 is displaced
upward and the volume in pressure chamber 150 is increased, there
is a negative pressure in pressure chamber 150. With this
operation, suction valve 120a is opened and the liquid is supplied
from suction side flow passage 170a into pressure chamber 150. At
this time, by the action of discharge valve 120b, there is no
backflow of the liquid from discharge side flow passage 170b to
pressure chamber 150. Then, piezoelectric oscillator 130 is
displaced in the opposite direction, and the volume of pressure
chamber 150 is reduced. Then, since the pressure in pressure
chamber 150 is raised, discharge valve 120b is opened and the
liquid is discharged toward discharge side flow passage 170b. At
this time, since suction valve 120a operates, there is no backflow
of the liquid from pressure chamber 150 to suction side flow
passage 170a. Piezoelectric pump 100 functions as a pump by
repeating the above-mentioned operations, and the liquid can flow
in one direction.
[0008] However, in conventional pumps, the flow passage from the
suction side flow passage to the discharge side flow passage via
the pressure chamber is formed in being bent. For example, in
piezoelectric pump 100 shown in FIG. 10, suction side flow passage
170a and discharge side flow passage 170b are formed under pressure
chamber 150, and are each connected with suction port 121 a and
discharge part 120b arranged on the lower surface of pressure
chamber 150. Accordingly, when piezoelectric pump 100 operates and
the liquid flows along the flow passage, the flow direction of the
liquid is bent at a point where the liquid flows from suction side
flow passage 170a into pressure chamber 150. The flow direction of
the liquid which has passed through pressure chamber 150 is bent
once again where the liquid flows from pressure chamber 150 to
discharge side flow passage 170b. In this way, when the flow of the
liquid is changed rapidly, the pressure of the liquid is largely
lost. As a result, the amount of flow of the liquid passing through
the flow passage is reduced, and therefore the pump efficiency is
decreased. The decrease in pump efficiency indicates a decrease in
the cooling efficiency of the cooling system.
[0009] Further, in piezoelectric pump 100, suction port 121a,
discharge port 121 b, and respective flow passages 170a, 170b are
positioned on/under the lower surface of pressure chamber 150.
Accordingly, the thickness obtained by adding the thickness of
pressure chamber 150 and the thickness of flow passages 170a, 170b
means that the pump has a substantial thickness. The pump is
incorporated in electronic equipment such as portable personal
computers, and therefore it is desirable to make the pump thinner
in order to reduce the thickness of electronic equipment.
DISCLOSURE OF INVENTION
[0010] The present invention has its object to provide a diaphragm
pump that enables an increase in pump efficiency by reducing the
pressure loss of liquid and that enables reduction in thickness.
Also, the present invention has its object to provide a cooling
system that enables an increase in cooling efficiency by being
provided with the diaphragm pump.
[0011] To achieve the above-mentioned object, a diaphragm pump
according to the present invention includes: [0012] a pressure
chamber formed into a flat shape and is filled up with liquid;
[0013] a suction side flow passage and a discharge side flow
passage disposed at both ends of the pressure chamber so that axes
thereof are aligned with each other and are connected with the
pressure chamber; [0014] check valves, respectively disposed on the
suction side flow passage and the discharge side flow passage, at
least one of the check valves being tilted relative to the
direction of the axes; and
[0015] at least one diaphragm disposed on at least one of an upper
surface and a lower surface of the pressure chamber and for
oscillation to make a volume of the pressure chamber variable.
[0016] According to the present invention, the suction side flow
passage and the discharge side flow passage are disposed at both
ends of the pressure chamber so that the pressure chamber is
sandwiched between the flow passages and the flow passages are
connected with the pressure chamber. The suction side flow passage
and the discharge side flow passage are extended in the same
direction so that axes thereof are aligned with each other.
Therefore, the flow passage for the pump, including the respective
flow passages and the pressure chamber, is formed in a straight
line without being bent, and thus the pressure loss of the liquid
is reduced and the liquid flows efficiently. Also, check valves
respectively disposed in the flow passages are tilted relative to
the axial direction of these flow passages, namely, the flow
direction of the liquid, and thus the pressure loss of the liquid
is further reduced. Additionally, since the pressure chamber is
formed into a flat shape and, since the suction side flow passage
and the discharge side flow passage are disposed at both ends of
the pressure chamber, the whole of the pump is reduced in
thickness. The diaphragm is arranged on at least one upper surface
and one the down surface of the pressure chamber so as to operate
on a surface having a large area in the flat-shaped pressure
chamber, and thus oscillation by the diaphragm is transmitted to
the pressure chamber efficiently. Therefore, the driving source is
reduced in size, work is saved, and the size of the pump is also
reduced.
[0017] Each of the flow passages may be formed so that the axes
thereof are positioned at the center of a cross-sectional shape of
the pressure chamber on a surface orthogonal to the axes.
Accordingly, the flow of the liquid in the pressure chamber is even
around the axes. With this arrangement, since the axes of the
respective flow passages approximately pass through the center of
the pressure chamber, the space in the pressure chamber is
approximately symmetric relative to the axes. Accordingly, the flow
passage of the liquid is approximately symmetric relative to the
axes, and thus the pressure loss of the liquid in the pressure
chamber is reduced.
[0018] Each cross-sectional shape of flow passages and the pressure
chamber is formed in an approximate rectangle in cross section. In
this case, these can be formed by a cutting process or the like,
and thus manufacturing is easy. In particular, when the lower
surfaces of the flow passages and the pressure chamber are formed
on the same surface, manufacturing is easy. Further, since the flow
passage is made flatly, the liquid is circulated efficiently. In
order to further reduce the pressure loss of the liquid, the length
of the pressure chamber, viewed from an upper surface in a
direction orthogonal to the axes, may be continuously shortened
toward the suction side flow passage or toward the discharge side
flow passage. Also, a height of the pressure chamber may be
continuously lowered toward the suction side flow passage or the
discharge side flow passage. In both cases, the section of the
pressure chamber is made smaller continuously toward the respective
flow passages, and thus the pressure loss of the liquid in the
pressure chamber is reduced.
[0019] In the diaphragm pump according to the present invention, at
least one groove may be formed in a peripheral wall of the pressure
chamber and can accelerate the flow of the liquid downstream in a
flow direction. The groove may have a part with an opening opened
to the pressure chamber, into which the liquid flows, and a side
part with an opening opened to a peripheral wall surface of the
pressure chamber, from which the liquid is discharged downstream in
the flow direction. The groove may be extended in a radial
direction while a point in the vicinity of the entrance of the
discharge side flow passage is set as a center. By arranging the
groove, when pressure is applied to the pressure chamber by the
diaphragm, the liquid is discharged from the side part with an
opening downstream and the flow of liquid is accelerated.
[0020] The diaphragm pump may include: at least one intake opened
to an upper surface of the suction side flow passage and is used to
introduce bubbles mixed in the liquid; and a sealed space connected
with the intake and is used to collect the introduced bubbles. The
intake may be positioned in the suction side flow passage upstream
relative to the check valve. Bubble collection means like this are
arranged in this way, and thus the bubbles mixed in the liquid are
collected and are prevented from entering the pressure chamber. In
this way, by removing bubbles from the flow passages and the
pressure chamber, the pressure loss of the liquid is further
reduced. The intake is positioned in the suction side flow passage
upstream relative to the check valve, and thus the bubbles are
efficiently prevented from entering the pressure chamber.
[0021] The diaphragm pump is a so-called piezoelectric pump in
which the driving source is a piezoelectric element. The
piezoelectric element enables a reduction in the size and thickness
of the pump.
[0022] Further, the above-mentioned diaphragm pump is available for
a cooling system that has a closed-structure flow passage for
circulating liquid discharged from the discharge side flow passage
in the diaphragm pump and for returning the liquid to the suction
side flow passage. The cooling system cools electric equipment
efficiently. In particular, the cooling system having a pump with
the bubble collection means circulates the liquid efficiently for a
long period because the bubbles in the flow passage are
collected.
[0023] Additionally, in this description, a "flat" pressure chamber
is a pressure chamber in which a length of the pressure chamber in
the height direction is shorter than one-half of the maximum length
of the pressure chamber viewed from the upper surface in the axial
direction, and than one-half of the maximum length in the direction
orthogonal to the axis.
[0024] According to the present invention, by adding ideas to the
structure of the diaphragm pump, the pressure loss of the liquid is
reduced and the pump is improved in pump efficiency and is reduced
in thickness. Also, the cooling system is provided with the
diaphragm pump, and thus the cooling system is improved in cooling
efficiency and is reduced in thickness.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 shows schematic views of a cooling system provided
with a piezoelectric pump of a first embodiment according to the
present invention,
[0026] FIG. 1(a) is a plan view showing a liquid passage in the
cooling system, and
[0027] FIG. 1(b) is a sectional view along line X-X in FIG.
1(a).
[0028] FIG. 2 shows the piezoelectric pump of the first embodiment,
FIG. 2(a) is a lateral section view, and FIG. 2(b) is a
longitudinal section view viewed from an upper surface side.
[0029] FIG. 3 shows the piezoelectric pump of a second embodiment,
FIG. 3(a) is a lateral section view, and FIG. 3(b) is a
longitudinal section view viewed from an upper surface side.
[0030] FIG. 4 is a perspective enlarged view showing one returning
groove and a flow direction of liquid.
[0031] FIG. 5 is a partial enlarged view showing a modification of
the shapes of returning grooves.
[0032] FIG. 6 is a section view showing a modification of the shape
of a pressure chamber.
[0033] FIG. 7 shows one example of a piezoelectric pump according
to a third embodiment.
[0034] FIG. 8 shows another example of a piezoelectric pump
according to the third embodiment.
[0035] FIG. 9 shows further another example of a piezoelectric pump
according to the third embodiment.
[0036] FIG. 10 is a section view showing a conventional
piezoelectric pump.
BEST MODE FOR CARRYING OUT THE INVENTION
[0037] Hereinafter, explanations are given of embodiments according
to the present invention with reference to drawings.
First Embodiment
[0038] FIG. 1 shows schematic views of a cooling system provided
with a piezoelectric pump of a first embodiment according to the
present invention, FIG. 1(a) is a plan view showing a liquid
passage in the cooling system, and FIG. 1(b) is a sectional view
along line X-X in FIG. 1(a).
[0039] Cooling system 10 shown in FIG. 1 is a water-cooled cooling
apparatus preferably used for providing cooling for electronic
equipment, such as a portable personal computer. Cooling system 10
is roughly provided with flow passage unit 60 in which circulation
flow passage 60a is formed and piezoelectric pump 1 connected to
flow passage unit 60 and is used to circulate liquid in the flow
passage. Flow passage unit 60 and piezoelectric pump 1 provide a
closed-structure flow passage. Inside the flow passage, liquid to
be circulated is filled up.
[0040] In flow passage unit 60, circulation flow passage 60a is
formed in a predetermined pattern. There are no particular
limitations to the sectional shape of circulation flow passage 60a,
and may be rectangular or circular. In the case of flow passage
unit 60 having a flat shape as in the first embodiment, circulation
flow passage 60a is preferably formed in a rectangle in the cross
section. Since a sectional shape of flat-shaped flow passage unit
60 is a shape in which plate members are overlaid, circulation flow
passage 60a is formed in a rectangle in cross section, for example,
a groove is formed in one plate member and is joined with another
plate member, thereby forming circulation flow passage 60a easily.
Piezoelectric pump 1 is connected to both ends of circulation flow
passage 60a, and thus is formed in one closed-structure flow
passage in association with circulation flow passage 60a. Cooling
system 10 effects the operation of piezoelectric pump 1 such that
the liquid is circulated in circulation flow passage 60a to
dissipate the heat of the liquid that is heated by the parts that
have been heated.
[0041] Hereinafter, piezoelectric pump 1 is explained in detail
with reference to FIG. 2. FIG. 2 shows the piezoelectric pump of
the first embodiment, FIG. 2(a) is a lateral section view, and FIG.
2(b) is a longitudinal section view viewed from an upper surface
side.
[0042] Piezoelectric pump 1 is provided with pressure chamber 50 in
which a part is formed by piezoelectric oscillator 30, and suction
port 21 a and discharge port 21 b are each connected to pressure
chamber 50. Suction valve 20a and discharge valve 20b are
respectively arranged in the vicinity of suction port 21a and
discharge port 21b. When piezoelectric oscillator 30 oscillates,
the pressure in pressure chamber 50 is changed, and the liquid
flows from suction port 21 a to discharge port 21 b in the
direction indicated by the arrows in FIG. 2.
[0043] Pressure chamber 50 is arranged between lower plate 11 and
upper plate 12 which provide a cabinet for piezoelectric pump 1.
Pressure chamber 50 is formed in a flat shape with a rectangular
lower surface. At one end of pressure chamber 50, suction port 21a
into which the liquid flows, is formed, and at the other end,
discharge port 21b from which the liquid flows, is formed. Both
suction port 21a and discharge port 21b are positioned on the
center line in the longitudinal direction of pressure chamber 50
formed in the rectangle viewed from the upper surface.
[0044] Suction side flow passage 70a connected with circulation
flow passage 60a shown in FIG. 1 is formed so that it is connected
with suction port 21a, and discharge side flow passage 70b
similarly connected with circulation flow passage 60a is formed so
that it is connected with discharge port 21b. Suction side flow
passage 70a and discharge side flow passage 70b are arranged in a
line on the center line and are extended in the same direction
while pressure chamber 50 is positioned between these flow
passages. Suction side flow passage 70a and discharge side flow
passage 70b are formed having similar shapes, and sections thereof
are rectangles. Flow passage 70a and flow passage 70b are formed in
rectangles in the cross section, and thus they can be formed easily
by the cutting process or the extruding process.
[0045] A height of pressure chamber 50 is approximately similar to
that of suction side flow passage 70a. Also, the flow passage in
piezoelectric pump 1 is formed into a flat shape by positioning the
lower surface of pressure chamber 50 and the lower surfaces of
suction side flow passage 70a and discharge side flow passage 70b
on the same plan.
[0046] Piezoelectric oscillator 30 is prepared as a diaphragm in
which an oscillating plate (not shown) is put between two
piezoelectric elements (not shown) which are bonded together, and
is arranged so as to operate on the upper surface of flat-shaped
pressure chamber 50. Also, an electrode (not shown) for applying a
voltage to the piezoelectric elements is formed. By applying an
alternating voltage to piezoelectric oscillator 30 structured in
this way, piezoelectric oscillator 30 bends and oscillate in the
thickness direction of the plate.
[0047] Lead zirconate titanate ceramic materials may be used, for
example, as piezoelectric elements. The oscillating plate and the
piezoelectric elements are bonded together by various techniques in
accordance with the materials of the oscillating plate. For
example, when ceramic or silicon is used as the oscillating plate,
the piezoelectric elements can be integrated with the oscillating
plate by a print firing method, a sputtering method, a sol-gel
method, or a chemical vapor method. Incidentally, in the first
embodiment, the piezoelectric elements are used as a driving source
to oscillate the diaphragm, however, the driving source is not
limited to piezoelectric elements and may be anything capable of
oscillating the diaphragm.
[0048] In suction side flow passage 70a and discharge side flow
passage 70b, suction valve 20a and discharge valve 20b made of thin
metal plates, such as aluminum, are respectively provided. Valves
20a, 20b are arranged so as to diagonally intersect the flow
direction of liquid. As to both valves 20a, 20b, upstream ends in
the flow direction are supported by cantilevers and downstream ends
are free ends abutting on side walls of flow passages 70a, 70b
without water load. Accordingly, suction valve 20a opens suction
side flow passage 70a when negative pressure is generated in
pressure chamber 50, and closes flow passage 70a when positive
pressure is generated in pressure chamber 50. On the other hand,
discharge valve 20b closes flow passage 70b when negative pressure
is generated in pressure chamber 50, and closes flow passage 70b
when positive pressure is generated.
[0049] Additionally, sectional shapes of suction side flow passage
70a and discharge side flow passage 70b may be circles or so-called
D-shapes in which a part of a circle is cut by a straight line.
However, flow passages 70a, 70b are formed in a rectangle in the
cross section as in the first embodiment, thereby forming valves
20a, 20b in simple shapes. Further, valves 20a, 20b can be attached
by a relatively easy method, for example, by bonding one end of a
valve member to one wall face in a flow passage.
[0050] Next, explanations are given of the operation of
piezoelectric pump 1 structured as described above.
[0051] First, a voltage of a predetermined polarity is applied to
piezoelectric oscillator 30, and piezoelectric oscillator 30 is
displaced so as to have an upward convex orientation in FIG. 2.
Then, the volume of pressure chamber 50 is increased, and the
pressure in pressure chamber 50 becomes negative pressure. With
this operation, suction valve 20a is displaced and suction port 21a
is opened, and the liquid flows into pressure chamber 50 via
suction side flow passage 70a and suction port 21a. At this time,
discharge valve 20b blocks discharge port 20b, and no liquid flows
from discharge port 21b.
[0052] Successively, a voltage of an inverse polarity to the above
polarity is applied to piezoelectric oscillator 30, and
piezoelectric oscillator 30 is displaced so as to have a downward
convex orientation in FIG. 2. With this operation, the volume in
pressure chamber 50 is reduced. Then, discharge valve 20b is
displaced and discharge port 21 b is opened, and the liquid is
discharged from pressure chamber 50 via discharge side flow passage
70b. At this time, suction valve 20a blocks suction side flow
passage 70a, and no liquid flows and is discharged into/from
suction port 21a.
[0053] By repeating the above-mentioned operations, suction of
liquid from suction port 21 a and discharge of the liquid from
discharge port 21 b are alternately repeated, and the liquid
pulsates. Accordingly, the liquid circulates through circulation
flow passage 60a in the direction indicated by arrows shown in FIG.
1(a) by the operation of piezoelectric pump 1.
[0054] In the first embodiment, the flow passage in piezoelectric
pump 1 is formed into a flat shape without being bent in the
thickness direction of the piezoelectric pump. Specifically, all of
suction side flow passage 70a, pressure chamber 50, and discharge
side flow passage 70b are formed on lower plate 11. Suction side
flow passage 70a and discharge side flow passage 70b are positioned
on a straight line and are extended in the same direction so that
presser chamber 50 is positioned between the passages. As a result,
the flow passage of piezoelectric pump 1 is formed in a flat shape
and in a straight line. Therefore, compared with the conventional
piezoelectric pump in which the flow passage is bent, piezoelectric
pump 1 can reduce the pressure loss caused by a change of the flow
direction of the liquid and can circulate the liquid efficiently.
Further, in piezoelectric pump 1, suction valve 20a and discharge
valve 20b are installed to tilt relative to the flow direction of
the liquid. Accordingly, compared with a valve arranged
orthogonally to the flow direction, suction valve 20a and discharge
valve 20b are displaced with a small force, and the pressure loss
of the liquid can be further reduced. As described above,
piezoelectric pump 1 is improved in pump efficiency compared with
the conventional one, and cooling system 10 (refer to FIG. 1) is
also improved in cooling efficiency with the improvement in pump
efficiency. Incidentally, in the first embodiment, both suction
valve 20a and discharge valve 20b are tilted relative to the flow
direction, however, it is possible to tilt only one discharge
valve.
[0055] Also, in the first embodiment, since flow passages 70a, 70b
are positioned at both ends of pressure chamber 50, the flow
passage is formed into a flat shape and the whole of piezoelectric
pump 1 is reduced in thickness. Further, since piezoelectric
oscillator 30 is arranged so as to operate on one surface that has
the large area of pressure chamber 50 formed in a flat rectangular
parallelepiped shape, the bending displacement of piezoelectric
oscillator 30 can be transmitted to pressure chamber 50
efficiently. Accordingly, relatively small piezoelectric oscillator
30 can obtain a sufficient amount of flow, and piezoelectric pump 1
can be reduced in size as a result. Additionally, in the first
embodiment, one piezoelectric oscillator is arranged on the upper
surface of pressure chamber 50, however, the number of
piezoelectric oscillators and their shape thereof are not limited.
For example, two piezoelectric oscillators are arranged for upper
and lower surfaces of pressure chamber 50.
[0056] As described above, cooling system 1 using piezoelectric
pump 1 that enables a reduction in thickness and an increase in
pump efficiency can circulate the liquid efficiently. Further, for
example, by arranging parts that have been heated directly to or in
the vicinity of flow passage unit 60, heat from the parts can be
dissipated efficiently.
Second Embodiment
[0057] In the first embodiment, the pressure chamber is formed in a
rectangular parallelepiped shape, however, the pressure chamber may
be formed so that the cross-sectional area of the pressure chamber
is gradually varied in order to reduce the resistance of the
liquid.
[0058] FIG. 3 shows the piezoelectric pump of the second embodiment
according to the present invention. Piezoelectric pump 2 shown in
FIG. 3 is formed so that pressure chamber 50' is formed in a
streamlined shape. On peripheral walls of pressure chamber 50',
structural parts (retuning grooves 11a) for accelerating the flow
of the liquid are arranged. The other structures are similar those
of piezoelectric pump 1 shown in FIG. 2, and the same numeral
references are applied to the structural parts having the same
functions and explanations thereof are omitted.
[0059] Pressure chamber 50', as shown in FIG. 3(b), is provided
with peripheral wall surface 11e in an approximate streamlined
shape viewed from the upper surface. Peripheral wall surface 11e is
arranged vertically to bottom part 11b of pressure chamber 50'.
Also, peripheral wall surfaces 11e are respectively connected with
suction port 21 a and discharge port 21 b, and are bent in an arc
shape toward the outside. Incidentally, the arc shape is preferably
set, as appropriate, in accordance with the kind of liquid or
characteristics of piezoelectric oscillator 30 so that the
resistance of the liquid is reduced as far as possible.
[0060] A plurality of retuning grooves 11a is formed on the
peripheral wall of pressure chamber 50' so as to open peripheral
wall surface 11e. In the second embodiment, five retuning grooves
11 a are arranged at predetermined intervals to have the same
groove width. Also, respective retuning grooves 11a are extended
from a point (not shown) as the center in the vicinity of discharge
port 21 b in the radiation direction. In other words, opening parts
of returning grooves 11a are directed to the point in the vicinity
of discharge port 21b. Preferably, the point is positioned at the
center of discharge port 21b.
[0061] A detailed shape of returning groove 11a is explained with
reference to FIG. 4. FIG. 4 is a perspective enlarged view showing
one returning groove-11a and the flow direction of liquid around
groove 11a. As shown in FIG. 4, returning groove 11a is opened to
upper edge surface 11c, the upper surface of the peripheral wall,
and to peripheral wall surface 11e. Also, returning groove 11a
gradually becomes deeper toward one end (side of peripheral wall
surface 11e).
[0062] On the peripheral side of upper edge surface 11c, convex
part 11d having a predetermined height relative to upper edge
surface 11c is formed. In the second embodiment, piezoelectric
oscillator 30 (refer to FIG. 3(a)) is positioned on the upper
surface of convex part 11a. Accordingly, a predetermined space is
formed between upper edge surface 11 c and piezoelectric oscillator
30, and the space is a part of pressure chamber 50'. With this
arrangement, when piezoelectric oscillator 30 is displaced so as to
have a downward convex orientation, the liquid flows into the
opening part at the upper surface side of returning groove 11a,
passes through retuning groove 11a, and is discharged from the
opening part of peripheral wall surface 11e.
[0063] In piezoelectric pump 2 arranged as described above,
peripheral wall surface 11e in pressure chamber 50' is formed in a
streamlined shape, and the cross-sectional area thereof
continuously becomes smaller toward suction side flow passage 70a
and discharge side flow passage 70b. Accordingly, the resistance
between the liquid and peripheral wall surface 11e is reduced, and
the pressure loss in pressure chamber 50' is further reduced. Also,
when piezoelectric oscillator 30 is displaced and the liquid is
discharged from discharge side flow passage 70b (refer to FIG. 3),
the liquid in the retuning groove 11a is discharged toward
discharge port 21 b. Therefore, the flow of the liquid in pressure
chamber 50' is accelerated, and piezoelectric pump 2 is further
improved in pump efficiency. In particular, since each retuning
groove 11a is opened toward discharge port 21 b, the liquid
discharged from retuning groove 11a accelerates the flow of the
liquid more efficiently.
[0064] Incidentally, the number of retuning grooves 11a and the
shape thereof, and the height of convex part 11d are preferably
set, as appropriate, in accordance with the kind of liquid or the
shape of discharge port 20b. For example, in accordance with the
shape of the pressure chamber and the position of the discharge
port, only one retuning groove 11 a may be formed. However, like
the second embodiment, in the case of pressure chamber 50' formed
symmetrically with respect to the axial line of flow passages 70a,
70b, as shown in FIG. 3(b), retuning grooves 11 a are preferably
formed symmetrically with respect to the axial line. With this
arrangement, the liquid flows symmetrically with respect to the
axial line.
[0065] As to the shape of retuning groove 11a, as shown in FIG. 5,
the width of retuning groove 11a' may be tapered toward pressure
chamber 50', and the liquid in returning groove 11a' may be
discharged from the tip of returning groove 11a' at high speed.
With this arrangement, the flow of the liquid is further
accelerated, and pump efficiency is further improved.
[0066] Also, in piezoelectric pump 2 shown in FIG. 3, while the
height of pressure chamber 50' is constant, peripheral wall surface
11e is bent so that the length orthogonal to the axial line of flow
passages 70a, 70b continuously becomes shorter toward flow passages
70a, 70b, and the cross-sectional area of pressure chamber 50'
becomes smaller toward suction port 21 a and discharge port 21b.
However, the shape of the pressure chamber is not limited to this
description as long as the cross-sectional area becomes smaller
continuously.
[0067] For example, as shown in FIG. 6, taper 12a may be arranged
at the corner part of pressure chamber 50''. In other words, the
height of pressure chamber 50'' is continuously lowered toward
suction port 21a or discharge port 21b so that the cross-sectional
area thereof becomes smaller. With this arrangement, the resistance
of the liquid passing through pressure chamber 50'' is reduced, and
the pressure loss of the liquid is reduced.
Third Embodiment
[0068] Generally, a closed-structure flow passage in cooling system
10 shown in FIG. 1 is filled up with the liquid so that no bubbles
remain. However, for example, there is a case in which dissolved
oxygen is changed into bubbles and the bubbles are mixed into the
liquid. In a piezoelectric pump, the existence of bubbles inside
the flow passage causes a reduction in pump efficiency. Further,
the existence of bubbles inside the closed-structure flow passage
causes a reduction in cooling efficiency of cooling system 10.
[0069] So, in order to further improve pump efficiency, in addition
to the two above-mentioned embodiments, a piezoelectric pump may be
provided with means for collecting bubbles mixed in the liquid.
[0070] Respective piezoelectric pumps 3, 3', 3'' shown in FIG. 7 to
FIG. 9 are provided with gaseous chambers 35, 35', 35''. FIGS.
7(a), 8(a) and 9(a) are lateral section views of piezoelectric
pumps 3, 3', 3'', and FIGS. 7(b), 8(b) and 9(b) are longitudinal
section views of gaseous chambers 35, 35', 35''.
[0071] Piezoelectric pump 3 shown in FIG. 7 has gaseous chamber 35
over piezoelectric oscillator 30. The other structures are similar
to those of piezoelectric pump 1 shown in FIG. 2, and the same
numeral references are applied to the structural parts having the
same functions as FIG. 2 and explanations thereof are omitted.
[0072] Gaseous chamber 35 is formed by piezoelectric oscillator 30
and by the cabinet of piezoelectric pump 3, and covers suction side
flow passage 70a and discharge side flow passage 70b.
[0073] At the somewhat upstream side to suction valve 20a, one
intake 35a for introducing bubbles into gaseous chamber 35 is
arranged. Intake 35 is a hole for connecting suction side flow
passage 70a and gaseous chamber 35 and is positioned on the upper
surface of suction side flow passage 70a.
[0074] When piezoelectric pump 3 is applied to cooling system shown
in FIG. 1, a closed-structure flow passage is formed by the flow
passage in cooling system 10 and gaseous chamber 35. Then, the flow
passage is completely filled up with the liquid to be circulated.
In other words, in the initial state of cooling system 10,
atmospheric pressure chamber 35 is also filled up with the
liquid.
[0075] In cooling system 10 structured like this, when bubbles are
generated in the liquid, the bubbles move through circulation flow
passage 60 (refer to FIG. 1) by the flow of the liquid. Then, the
bubbles which have moved along the upper wall of suction side flow
passage 70a are taken into intake 35a and float upward. At the same
time, the liquid in gaseous chamber 35 is pushed out from intake
35a by the bubbles, and the bubbles are collected in gaseous
chamber 35. With this operation, in piezoelectric pump 3, the
bubbles can be removed from the flow passage in cooling system 10,
and the liquid can be circulated without a reduction in pump
efficiency.
[0076] Incidentally, in the third embodiment, as shown in FIG.
7(b), the shape of the opening of intake 35a is formed in a circle.
There are no particular limitations to the shape of intake 35a, as
long as bubbles can be collected, for example, an oblong hole (not
shown) extending in the width direction of suction side flow
passage 70a may be formed. With this arrangement, bubbles moving
along the upper wall of flow passage 70a can be collected
efficiently. Further, when two intakes are provided, bubbles enter
gaseous chamber 35 through one of the intakes while liquid is
discharged from the other intake. In this way, the operation of
changing bubbles and liquid may be performed smoothly. Needless to
say, in order to collect bubbles efficiently, intake 35 may be
arranged so as to be higher relative to flow passage 70a, and
grooves and cut parts for guiding the bubbles to intake 35 may be
formed.
[0077] Additionally, piezoelectric pump according to the third
embodiment may be variously changed as shown FIGS. 8 and 9. In
piezoelectric pump 3' in FIG. 8, piezoelectric oscillator 30 is
arranged on the lower surface of pressure chamber 50. In
piezoelectric pump 3'' in FIG. 9, gaseous chamber 35'' is arranged
in a loop area. Both of piezoelectric pumps 3', 3'' are not
different from piezoelectric pumps 3 substantially, and gaseous
chambers 35, 35', 35'' function similarly.
[0078] As described above, according to the third embodiment,
piezoelectric pump 3 is provided with gaseous chamber 35, and
bubbles generated in liquid can be collected. Therefore,
piezoelectric pump 3 is improved in pump efficiency. Also, high
cooling efficiency in cooing system 10 is maintained for a long
period. Further, in the cooling system 10 having piezoelectric
pumps 3, 3', 3'' explained in the third embodiment, when liquid is
expanded by a change of environmental temperature or the like, the
volume change is absorbed by gaseous chambers 35, 35', 35''.
Therefore, piezoelectric pumps 3, 3', 3'' and the flow passage in
cooling system are prevented from being broken.
[0079] Representative embodiments have been explained, however,
elements explained in each embodiment may be combined freely as far
as possible.
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