U.S. patent application number 12/109584 was filed with the patent office on 2008-12-11 for diaphragm air pump.
Invention is credited to Hitoshi Onishi, Satoshi Yamada.
Application Number | 20080304983 12/109584 |
Document ID | / |
Family ID | 40096051 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080304983 |
Kind Code |
A1 |
Yamada; Satoshi ; et
al. |
December 11, 2008 |
DIAPHRAGM AIR PUMP
Abstract
A diaphragm air pump includes a diaphragm; and upper and lower
housings that interpose the diaphragm such that a variable volume
chamber is formed over and under the diaphragm. The diaphragm air
pump vibrates the diaphragm to obtain a pump operation, a circular
concave portion into which the diaphragm that is circular in plan
view is fitted is formed in any one of the upper and lower
housings, a ring-shaped groove for housing a seal member is formed
in the other, the ring-shaped groove having inner and outer
diameters which are set across the circular concave portion, and a
ring-shaped elastic seal member which is compressively deformed
across the periphery of the diaphragm by the upper and lower
housings is housed in the ring-shaped groove.
Inventors: |
Yamada; Satoshi;
(Niigata-ken, JP) ; Onishi; Hitoshi; (Niigata-ken,
JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
40096051 |
Appl. No.: |
12/109584 |
Filed: |
April 25, 2008 |
Current U.S.
Class: |
417/413.2 |
Current CPC
Class: |
F04B 43/04 20130101 |
Class at
Publication: |
417/413.2 |
International
Class: |
F04B 43/04 20060101
F04B043/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 8, 2007 |
JP |
2007-152411 |
Claims
1. A diaphragm air pump comprising: a diaphragm; and upper and
lower housings that interpose the diaphragm such that a variable
volume chamber is formed over and under the diaphragm, wherein the
diaphragm air pump vibrates the diaphragm to obtain a pump
operation, a circular concave portion into which the diaphragm that
is circular in plan view is fitted is formed in any one of the
upper and lower housings, a ring-shaped groove for housing a seal
member is formed in the other, the ring-shaped groove having inner
and outer diameters which are set across the circular concave
portion, and a ring-shaped elastic seal member which is
compressively deformed across the periphery of the diaphragm by the
upper and lower housings is housed in the ring-shaped groove.
2. The diaphragm air pump according to claim 1, wherein the
diaphragm comprises a piezoelectric vibrator.
3. The diaphragm air pump according to claim 2, wherein the
piezoelectric vibrator comprises a unimorph-type piezoelectric
vibrator in which a piezoelectric body is stacked on a shim formed
of a conductive metal thin plate.
4. The diaphragm air pump according to claim 3, wherein the shim of
the piezoelectric vibrator has a larger diameter than the
piezoelectric body, and the circular concave portion of the lower
housing is composed of a large-diameter stepped portion into which
the shim is fitted and a small-diameter stepped portion in which
the piezoelectric body is housed in a non-contact manner.
5. The diaphragm air pump according to claim 1, wherein the
cross-sectional shape of the ring-shaped elastic seal member in a
free state is rectangular.
6. The diaphragm air pump according to claim 1, wherein the
cross-sectional shape of the ring-shaped elastic seal member in a
free state is circular.
7. The diaphragm air pump according to claim 1, wherein the
cross-sectional shape of the ring-shaped elastic seal member in a
free state is elliptical oval.
8. The diaphragm air pump according to claim 1, wherein the
cross-sectional shape of the ring-shaped elastic seal member in a
free state is oval.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to Japanese Patent
Application JP2007-152411 filed in the Japanese Patent Office on
Jun. 8, 2007, the entire contents of which being incorporated
herein by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a diaphragm air pump which
vibrates a diaphragm in a reciprocating manner to obtain a pump
action.
[0004] 2. Description of the Related Art
[0005] The disclosure examines a method in which a piezoelectric
air pump using a piezoelectric vibrator is used for cooling a heat
generating source (for example, CPU) of a notebook PC, for
example.
[0006] The piezoelectric vibrator has an amplitude of several tens
to several hundreds .mu.m order. As a piezoelectric vibrator
vibrates in a variable volume chamber, the volume of the chamber is
sufficiently reduced such that jet gas (air) can be transferred,
and the heated air around the heat generating source is moved by
the gas flow such that the heat generating source is cooled.
[0007] The piezoelectric vibrator is constructed by stacking a
piezoelectric body on at least one of the top and bottom surfaces
of a shim (conductive thin metal plate). The thickness of the
piezoelectric vibrator can be reduced into less than 1 mm as a
whole. Further, the variable volume chamber formed over and under
the piezoelectric vibrator has such a small volume as to supply and
discharge compressive air through the vibration of the
piezoelectric vibrator. Therefore, the thickness of a piezoelectric
gas jetting device can be significantly reduced in such a manner
that the device is used for cooling such an apparatus as a notebook
PC having a small space. Such a gas jetting device is disclosed in
Japanese Patent Unexamined Publication No. 2005-256834 and U.S.
Pat. Nos. 6,801,430 and 6,123,145.
[0008] In the piezoelectric air pump, a ring-shaped seal member
formed of an elastic material is provided on the top and bottom
surfaces of the piezoelectric vibrator, in order to secure an
air-tight structure of the piezoelectric vibrator (diaphragm). That
is, the ring-shaped seal member is interposed between the top
periphery of the diaphragm and an upper housing and between the
bottom periphery of the diaphragm and a lower housing,
respectively. It has been considered to be essential that the
ring-shaped seal member is provided on both the top and bottom
surfaces of the diaphragm. However, according to the analysis of
the present inventors, a diaphragm air pump in which liquid leak
does not need to be considered may not have a ring-shaped seal
member provided on both the top and bottom surfaces. By improving a
seal structure, air seal can be realized by a single ring-shaped
seal member.
SUMMARY
[0009] A diaphragm air pump includes a diaphragm and upper and
lower housings that interpose the diaphragm such that a variable
volume chamber is formed over and under the diaphragm. The
diaphragm air pump vibrates the diaphragm to obtain a pump
operation, and the variable volume chambers provided on the top and
bottom of the diaphragm, respectively, can be air-sealed by one
ring-shaped elastic seal member.
[0010] In the diaphragm air pump, a circular concave portion into
which the diaphragm that is circular in plan view is fitted is
formed in any one of the upper and lower housings, a ring-shaped
groove for housing a seal member is formed in the other, the
ring-shaped groove having inner and outer diameters which are set
across the circular concave portion, and a ring-shaped elastic seal
member which is compressively deformed across the periphery of the
diaphragm by the upper and lower housings is housed in the
ring-shaped groove.
[0011] The diaphragm may be a piezoelectric vibrator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of an embodiment in which a
diaphragm according to the present invention is applied to a
piezoelectric gas jet generating device;
[0013] FIG. 2 is an exploded perspective view of the embodiment;
and
[0014] FIG. 3 is a partially expanded cross-sectional view of the
embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0015] FIGS. 1 to 3 are diagrams showing an embodiment of the
invention which is applied to a piezoelectric air pump (gas jet
generating device) 100. The piezoelectric air pump 100 includes a
piezoelectric vibrator 10, an upper housing 20, a lower housing 30,
and a ring-shaped elastic seal member 40. The upper and lower
housings 20 and 30 are formed of a rigid resin material (for
example, PBT or PPS), and the ring-shaped elastic seal member 40 is
formed of a rubber material (for example, EPDM).
[0016] The piezoelectric vibrator 10 is a unimorph-type
piezoelectric vibrator which includes a shim 11 and a piezoelectric
body 12 stacked on one surface of the shim 11 (FIG. 3). The shim 11
is formed of a conductive metal thin plate, for example, a thin
plate such as stainless steel with a thickness of 50 to 200 .mu.m,
42 alloy or the like. The piezoelectric body 12 is formed of a
piezoelectric ceramic material such as PZT (Pb(Zr, Ti)O.sub.3) with
a thickness of 50 to 300 .mu.m. The piezoelectric body 12 is
subjected to polarization processing in the top and bottom
direction thereof. When an alternating electric field is applied to
the shim 11 and the exposed surfaces of the piezoelectric body 12
(the bottom and top surfaces of the piezoelectric body 12) through
a feed line 13, a cycle is repeated where one of the bottom and top
surfaces of the piezoelectric body 12 extends and the other
contracts. Accordingly, the shim 11 (piezoelectric vibrator 10)
vibrates.
[0017] The lower housing 30 has a stepped circular concave portion
31 formed therein. The stepped circular concave portion 31 is
composed of a small-diameter circular concave portion 32, in which
the piezoelectric body 12 is positioned in a non-contact manner,
and a large-diameter circular concave portion 33 into which the
shim 11 is fitted. The large-diameter circular concave portion 33
is formed on the small-diameter circular concave portion 32 such
that the concave portions are concentric with each other. The depth
and thickness of the large-diameter circular concave portion 33
correspond to the diameter and thickness of the shim 11. When the
shim 11 is fitted into the large-circular concave portion 33, the
surface of the shim 11 becomes flush with a peripheral abutting
surface 34 of the lower housing 30. The depth of the small-diameter
circular concave portion 32 is set in such a manner that when the
piezoelectric vibrator 10 (shim 11) is fitted into the stepped
circular concave portion 31 (large-diameter circular concave
portion 33), a lower variable volume chamber 35 with a minute space
is formed between the piezoelectric body 12 and the bottom of the
small-diameter circular concave portion 32. As such, only the shim
11 of the piezoelectric vibrator 10 is interposed between the upper
and lower housings, and the piezoelectric body 12 is positioned so
as not to come in contact with the housing. Therefore, the
deformation (vibration) of the piezoelectric vibrator 10 is easily
performed, which makes it possible to increase the amplitude of
vibration.
[0018] Meanwhile, the upper housing 20 has a circular concave
portion 21 and a ring-shaped groove 22 concentric with the circular
concave portion 21. The outer diameter D of the ring-shaped groove
22 is set to be larger than the outer diameter of the
large-diameter circular concave portion 33, and the inner diameter
d of the ring-shaped groove 22 is set to be smaller than the outer
diameter of the large-diameter circular concave portion 33. That
is, the inner and outer diameters of the ring-shaped groove 22 are
set across the largest-diameter portion (edge) of the
large-diameter circular concave portion 33. The depth of the
circular concave portion 21 is set in such a manner that when the
peripheral abutting surface 23 of the upper housing 20 is abutted
on the peripheral abutting surface 34 of the lower housing 30, an
upper variable volume chamber 24 with a minute space is formed
between the shim 11 of the piezoelectric vibrator 10 fitted into
the stepped circular concave portion 31 and the bottom of the
circular concave portion 21.
[0019] The ring-shaped elastic seal member 40 is inserted into the
ring-shaped groove 22 of the upper housing 20. The inner and outer
diameters of the ring-shaped elastic seal member 40 correspond to
those of the ring-shaped groove 22 and are set across the
outer-diameter edge of the shim 11 of the piezoelectric vibrator
10. Further, the depth of the ring-shaped groove 22 and the
thickness of the ring-shaped elastic seal member 40 are set in such
a manner that when the peripheral abutting surface 23 of the upper
housing 20 and the peripheral abutting surface 34 of the lower
housing 30 are abutted so as to be fastened through a fastening
screw 27, the ring-shaped elastic seal member 40 is compressed
20-30%. The ring-shaped elastic seal member 40 has a rectangular
cross-section in a free state. However, the ring-shaped elastic
seal member 40 may have a circular cross-section, an oval
cross-section, or an elliptical cross-section.
[0020] The upper and lower housings 20 and 30 have upper and lower
supply/discharge holes 26 and 36, respectively, through which the
upper and lower variable volume chambers 24 and 35 communicate with
the outside. The upper and lower supply/discharge holes 26 and 36
extend between the bottom surface of the upper and lower variable
volume chambers 24 and 35 and the side surface of the upper and
lower housings 20 and 30. The volume (cross-sectional area) of the
upper and lower variable volume chamber 24 and 35 is determined in
such a manner that the suction and discharge of air accompanied by
the vibration of the piezoelectric vibrator 10 is performed as
impulsively as possible and a compression ratio increases. Further,
the opening ends of the upper and lower supply/discharge holes 26
and 36 on the side surface of the piezoelectric air pump 100 are
disposed in a zigzag shape such that the positions thereof do not
coincide with each other in the vertical direction. The upper and
lower supply/discharge holes 26 and 36 can be connected to suitable
pipes so as to be opened in arbitrary positions.
[0021] As an index indicating what size the present piezoelectric
air pump 100 has, a specific dimensional example is described as
follows.
[0022] Upper housing 20 (Lower housing 30)=Square Of 35 mm in
length of about one
[0023] Total thickness of upper and lower housings 20 and 30=3
mm
[0024] Thickness of shim 11=0.2 mm
[0025] Thickness of piezoelectric body 12=0.2 mm
[0026] Gap between circular concave portion 21 and shim 11 in free
state (Depth of upper variable volume chamber 24)=0.15 mm
[0027] Gap between small-diameter concave portion 32 and
piezoelectric body 12 in free state (Depth of lower variable
chamber 35)=0.15 mm
[0028] Amplitude of piezoelectric vibrator 10=0.15 to 0.2 mm
[0029] In the above-described piezoelectric air pump 100, as an
alternating electric field is applied to the top and bottom
surfaces of the piezoelectric body 12 through the feed line 13, the
piezoelectric vibrator 10 vibrates in such a manner that the
amplitude of the central portion thereof that is circular in plan
view becomes the greatest. Then, in a stroke where the volume of
the upper variable volume chamber 24 (lower variable volume chamber
35) expands, the air is sucked into the upper variable volume
chamber 24 (lower variable volume chamber 35) from the upper
supply/discharge hole 26 (lower supply/discharge hole 36). In a
stroke where the volume of the upper variable volume chamber 24
(lower variable volume chamber 35) contracts, the air is discharged
into the upper supply/discharge hole 26 (lower supply/discharge
hole 36) from the upper variable volume chamber 24 (lower variable
volume chamber 35). The volumes (cross-sectional areas) of the
upper variable volume chamber 24 (lower variable volume chamber 35)
and the upper supply/discharge hole 26 (lower supply/discharge hole
36) are determined in such a manner that the suction and discharge
of air is performed as impulsively as possible. Therefore, the
movement of the air occurs in the vicinities of the opening end of
the upper supply/discharge hole 26 (lower supply/discharge hole
36), which makes it possible to obtain a cooling operation.
[0030] In the above-described embodiment, the terms of `upper` and
`lower` have been used for convenience of description. However, the
terms do not indicate the upper and lower relationship when the
piezoelectric air pump 100 is used.
[0031] In the above-described embodiment, a unimorph-type
piezoelectric vibrator is used as the piezoelectric vibrator 10.
However, a bimorph-type piezoelectric vibrator may be used, in
which a piezoelectric body is provided on the top and bottom
surfaces of a shim and of which the amplitude is large. Further,
the present invention can be applied to an air pump using a
diaphragm, in addition to a piezoelectric vibrator.
[0032] In the diaphragm pump according to the embodiment of the
invention, a circular concave portion to which a diaphragm that is
circular in plan view is fitted is formed in any one of upper and
lower housings, and a ring-shaped groove for housing a seal member
is formed in the other one, the ring-shaped groove having inner and
outer diameters which are set across the circular concave portion.
Further, a ring-shaped elastic seal member, which is compressively
deformed across the periphery of the diaphragm by the upper and
lower housings, is housed in the ring-shaped groove for housing the
seal member. Therefore, variable volume chambers provided on the
top and bottom of the diaphragm, respectively, can be air-sealed by
one ring-shaped elastic seal member.
[0033] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alternations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
of the equivalents thereof.
* * * * *