US20150023819A1

US20150023819A1 - Piezoelectric fan

Info

Publication number: US20150023819A1
Application number: US14/506,721
Authority: US
Inventors: Nobuhira TANAKA
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2012-04-17
Filing date: 2014-10-06
Publication date: 2015-01-22
Also published as: WO2013157346A1; JP5892240B2; JPWO2013157346A1

Abstract

A piezoelectric fan in which vibration of blades is unaffected by external noise includes a vibrating plate including blades and a base. First piezoelectric elements are attached to a side of a first blade adjacent to the base. Second piezoelectric elements are attached to a side of a second blade adjacent to the base. Third piezoelectric elements are attached to a side of a third blade adjacent to the base. A holder includes a supporting body and a holding member that sandwich the base therebetween. The holding member has a supporting portion and main-body fixing portions including respective main-body fixing holes. The main-body fixing portions extend from the supporting portion.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a piezoelectric fan that blows air by using a piezoelectric element as a drive source to a vibrate blade.
2. Description of the Related Art
Conventional piezoelectric fans that use a piezoelectric element as a drive source are described, for example, in Japanese Unexamined Patent Application Publication No. 2-33500 and International Publication No. 2009/119431.
The piezoelectric fan described in Japanese Unexamined Patent Application Publication No. 2-33500 includes a vibrating plate and piezoelectric elements. One end of the vibrating plate is divided into three blades, whereas the other end of the vibrating plate is provided with main-body fixing holes. The piezoelectric elements are attached to the respective blades. The piezoelectric element on the central blade and the piezoelectric elements on the right and left blades are polarized in opposite directions. When an alternating voltage of the same phase is applied to each of the piezoelectric elements, the central blade and the right and left blades vibrate in opposite phases. Vibration is suppressed at the fixed end of the vibrating plate, because vibration of the central blade and vibration of the right and left blades cancel each other out. The piezoelectric fan blows air by performing this operation.
The piezoelectric fan described in International Publication No. 2009/119431 includes a vibrating plate, piezoelectric elements, and a supporting body. The vibrating plate is composed of two separate blades. The piezoelectric elements are attached to the two blades in the same manner. The two blades are supported and coupled to each other in parallel by the supporting body. When alternating voltages of opposite phases are applied to the two piezoelectric elements, the piezoelectric fan operates in the same manner as that described above.
A piezoelectric fan illustrated in FIG. 6 was devised by the inventor of the present application using the prior art disclosed in Japanese Unexamined Patent Application Publication No. 2-33500 and International Publication No. 2009/119431. FIG. 6A is an external perspective view of a piezoelectric fan 10P, FIG. 6B is a plan view of the piezoelectric fan 10P, and FIG. 6C is a lateral view of the piezoelectric fan 10P.
The piezoelectric fan 10P includes a vibrating plate 11, piezoelectric elements 121, 122, 123, 131, 132, and 133 and supporting bodies 141P and 142P. Main- body fixing holes 151 and 152 are provided to secure the main body of the piezoelectric fan 10P, for example, to a destination housing to which air is supplied. Note that the piezoelectric elements 131 and 132 are not shown in FIGS. 6A-6C.
The vibrating plate 11 is integrally formed by three blades 111, 112, and 113 and a base 110P. The blades 111, 112, and 113 are arranged in the longitudinal direction of the base 110P in the following order: the blade 112, the blade 111, and the blade 113.
The piezoelectric element 121 is attached to one flat surface of the blade 111, the piezoelectric element 131 is attached to the other flat surface of the blade 111, the piezoelectric element 122 is attached to one flat surface of the blade 112, and the piezoelectric element 132 is attached to the other flat surface of the blade 112. The piezoelectric element 123 is attached to one flat surface of the blade 113, and the piezoelectric element 133 is attached to the other flat surface of the blade 113. The polarization direction of each piezoelectric element and the direction of voltage applied to the piezoelectric element are set such that the central blade 111 and the left and right blades 112 and 113 vibrate in opposite phases. When an alternating voltage is applied to each piezoelectric element, the piezoelectric fan 10P operates in the manner described above.
The supporting bodies 141P and 142P support the vibrating plate 11 by sandwiching the vibrating plate 11 from both flat sides of the base 110P.
The main- body fixing holes 151 and 152 pass through the base 110P and the supporting bodies 141P and 142P. For example, with screws inserted in the main- body fixing holes 151 and 152, the piezoelectric fan 10P is attached to a destination housing to which air is supplied.
In the piezoelectric fan 10P, the base 110P and the supporting bodies 141P and 142P are often bonded together by an adhesive.
The conventional piezoelectric fan illustrated in FIGS. 6A-6C is secured to an external housing (i.e., a housing to which the piezoelectric fan is to be attached) by inserting screws into the main- body fixing holes 151 and 152 as described above. This causes electrical conduction between the vibrating plate 11 and the external housing. As a result, noise may propagate through the external housing to the vibrating plate 11. If noise propagates to the vibrating plate 11, drive signals for driving the piezoelectric elements are disturbed by the noise and desired vibration cannot be obtained.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide a piezoelectric fan that prevents electrical conduction between a vibrating plate and an external housing, and reliably obtains desired vibration.
A piezoelectric fan according to a preferred embodiment of the present invention includes a vibrating plate including a base and a blade; a piezoelectric element attached to the blade; and a holding member including a supporting portion and a main-body fixing portion, the supporting portion being configured to support the base. The main-body fixing portion of the holding member extends from the supporting portion.
In this configuration, a main-body fixing hole of the main-body fixing portion is located in an area where the vibrating plate is not in contact with a supporting body. Therefore, even when the piezoelectric fan is secured to an external housing with conductive screws, the vibrating plate and the external housing are not electrically conducted to each other. It is thus possible to prevent external noise from propagating to the vibrating plate.
In a piezoelectric fan according to a preferred embodiment of the present invention, it is preferable that the blade be provided in a plurality, and that the main-body fixing portion be positioned between the plurality of blades.
In a piezoelectric fan according to a preferred embodiment of the present invention, the main-body fixing portion is preferably positioned to a blade side compared with the base in a plan view of the vibrating plate.
With this configuration, it is possible to provide a compact piezoelectric fan while providing the operation and effect described above. In particular, when the main-body fixing portion is positioned to the blade side compared with the supporting portion, it is possible to further reduce the size of the piezoelectric fan.
A piezoelectric fan according to a preferred embodiment of the present invention preferably has the following configuration. That is, the number of the plurality of blades is preferably three, for example, and the blades are arranged in a longitudinal direction of the supporting portion; and the blades at both ends in the direction of arrangement and the blade at the center in the direction of arrangement are driven to vibrate in opposite phases.
This shows a more concrete configuration of the piezoelectric fan. With this configuration, vibrations of the blades cancel each other out at the base and do not propagate to the outside. In the piezoelectric fan with this configuration, where a desired drive signal is reliably applied to each blade, the vibrations reliably cancel each other out.
In a piezoelectric fan according to a preferred embodiment of the present invention, the holding member is preferably made of an insulating material.
With this configuration, where the holding member is electrically insulated from the outside, it is possible to prevent noise from being superimposed on drive signals through the holding member.
Various preferred embodiments of the present invention ensure insulation between the vibrating plate and the external housing, and to stably obtain desired vibration.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D provide an external perspective view, a plan view, a lateral view, and a cross-sectional view of a piezoelectric fan 10 according to a first preferred embodiment of the present invention.

FIG. 2 illustrates a driving concept of the piezoelectric fan 10 according to the first preferred embodiment of the present invention.

FIG. 3 is a plan view of a holding member 142 according to the first preferred embodiment of the present invention.

FIGS. 4A-4C provide an external perspective view, a plan view, and a lateral view of a piezoelectric fan 10A according to a second preferred embodiment of the present invention.

FIGS. 5A-5C provide an external perspective view, a plan view, and a lateral view of a piezoelectric fan 10B according to a third preferred embodiment of the present invention.

FIGS. 6A-6C provide an external perspective view, a plan view, and a lateral view of a piezoelectric fan 10P according to a comparative example of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A piezoelectric fan according to a first preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1A is an external perspective view of a piezoelectric fan 10 according to the first preferred embodiment of the present invention. FIG. 1B is a plan view of the piezoelectric fan 10 according to the first preferred embodiment of the present invention. FIG. 1C is a lateral view of the piezoelectric fan 10 according to the first preferred embodiment of the present invention. FIG. 1D is a cross-sectional view taken along line A-A′ of the piezoelectric fan 10 according to the first preferred embodiment of the present invention. FIG. 2 illustrates a driving concept of the piezoelectric fan 10 according to the first preferred embodiment of the present invention. FIG. 3 is a plan view of a holding member 142 according to the first preferred embodiment of the present invention.
The piezoelectric fan 10 includes a vibrating plate 11, piezoelectric elements 121, 122, 123, 131, 132, and 133, and a holder 14.
The vibrating plate 11 is a flat plate including a first flat surface and a second flat surface opposite each other, and having a predetermined degree of stiffness. The vibrating plate 11 preferably is, for example, a 0.1-mm-thick stainless steel (SUS) plate, for example.
The vibrating plate 11 is integrally configured and defined by three blades 111, 112, and 113 and a base 110 that are preferably defined by a single unitary member, for example. The blades 111, 112, and 113 and the base 110 are long flat plates. The blades 111, 112, and 113 are arranged along the base 110 at predetermined intervals in the longitudinal direction of the base 110. The blades 111, 112, and 113 are arranged and connected in the longitudinal direction of the base 110 in the following order: the blade 112, the blade 111, and the blade 113. The longitudinal direction of the blades 111, 112, and 113 is perpendicular or substantially perpendicular to the longitudinal direction of the base 110, that is, perpendicular or substantially perpendicular to the direction of arrangement of the blades 111, 112, and 113.
End portions of the blades 111, 112, and 113, the end portions being connected to the base 110, are fixed ends of the blades 111, 112, and 113. The other end portions of the blades 111, 112, and 113, the other end portions being opposite the fixed ends, are free ends.
Widths (i.e., lengths in the short side direction) of the blades 111, 112, and 113 vary along their longitudinal direction. Specifically, the widths of the blades 111, 112, and 113 are shorter at the fixed ends than at the free ends. Thus, in plan view of the vibrating plate 11 (i.e., as viewed in the direction perpendicular or substantially perpendicular to the first flat surface and the second flat surface), a gap having a predetermined length is provided between the blade 111 and the blade 112, and a gap having a predetermined length is provided between the blade 111 and the blade 113.
The blades 112 and 113 at both ends are identical in shape. The width of the blade 111 at the center in the direction of arrangement preferably is about twice the width of the blades 112 and 113 at both ends in the direction of arrangement, for example.
The piezoelectric element 121 is attached to the first flat surface of the blade 111. The piezoelectric element 131 is attached to the second flat surface (i.e., a surface on the opposite side of the first flat surface) of the blade 111. The piezoelectric element 122 is attached to the first flat surface of the blade 112. The piezoelectric element 132 is attached to the second flat surface of the blade 112. The piezoelectric element 123 is attached to the first flat surface of the blade 113. The piezoelectric element 133 is attached to the second flat surface of the blade 113.
The piezoelectric elements 121, 122, 123, 131, 132, and 133 are long flat plates. Each piezoelectric element is polarized in the direction perpendicular or substantially perpendicular to its flat surfaces. The flat surfaces of each piezoelectric element are provided with electrodes configured to apply drive signals (not shown).
Each piezoelectric element is preferably defined by, for example, by a piezoelectric body made of PZT ceramics and electrodes on both principal surfaces of the piezoelectric body. When the vibrating plate 11 is an electrical conductor, the electrode on the side of the vibrating plate 11 can be omitted.
As illustrated in FIG. 2, the polarization direction of the piezoelectric element 121 is opposite that of the piezoelectric elements 122 and 123. Also, the polarization direction of the piezoelectric element 131 is opposite that of the piezoelectric elements 132 and 133. The polarization direction of the piezoelectric element 121 is the same as that of the piezoelectric element 131.
When an alternating voltage of the same phase is applied to the piezoelectric elements 121, 122, 123, 131, 132, and 133 polarized as described above, the blade 111 and the blades 112 and 113 vibrate in opposite phases. Vibration is suppressed or prevented at the fixed end of the vibrating plate, because vibrations of the blade 111 and the blades 112 and 113 cancel each other out.
The holder 14 includes a supporting body 141 and a holding member 142.
The supporting body 141 is preferably defined by a long flat plate substantially identical to the base 110. The supporting body 141 is preferably made of, for example, an insulating material such as glass epoxy resin. The supporting body 141 is attached to the first flat surface of the base 110 such that the longitudinal direction thereof coincides with that of the base 110.
The holding member 142 is preferably integrally defined by a supporting portion 160 and main- body fixing portions 161 and 162. The holding member 142 preferably is made of, for example, an insulating material such as glass epoxy resin. When the supporting body 141 and the holding member 142 are each made of an insulating material, noise from the outside is prevented from being superimposed on drive signals through the holding member 142. This significantly reduces or prevents negative effects of noise on vibration. The operation and effects described above are achieved as long as at least the main- body fixing portions 161 and 162 of the holding member 142 are made of an insulating material.
The supporting portion 160 is preferably defined by a long flat plate substantially identical to the base 110. The main- body fixing portions 161 and 162 protrude from an end surface of the supporting portion 160, the end surface being parallel or substantially parallel to the longitudinal direction in the flat surface of the supporting portion 160. The main- body fixing portions 161 and 162 are spaced apart by substantially the width of the blade 111. The main- body fixing portions 161 and 162 are provided with main-body fixing holes 151 and 152, respectively. For example, with metal screws inserted in the main-body fixing holes 151 and 152, the piezoelectric fan 10 is attached to an external housing, such as a destination housing to which air is supplied.
The holding member 142 is attached to the second flat surface of the base 110 such that the longitudinal direction of the supporting portion 160 coincides with that of the base 110. The main-body fixing portion 161 is positioned in the gap between the blade 111 and the blade 112, and the main-body fixing portion 162 is positioned in the gap between the blade 111 and the blade 113.
With this configuration, even when the piezoelectric fan 10 is attached to an external housing by inserting conductive fixing members, such as screws, into the main-body fixing holes 151 and 152, the vibrating plate 11 and the external housing are not electrically conducted (short-circuit) through the screws. Therefore, noise generated in another circuit board included in the external housing, or noise propagating from outside the housing, is prevented from propagating to the vibrating plate 11. It is thus possible to prevent noise from being superimposed on drive signals to drive the piezoelectric elements 121, 122, 123, 131, 132, and 133, and to stably vibrate the blades 111, 112, and 113 as desired.
The holding member 142 is attached to the vibrating plate 11 by bonding the supporting portion 160 and the base 110 together with an adhesive. Since the main-body fixing holes 151 and 152 are not provided in the supporting portion 160, there is no possibility that the main-body fixing holes 151 and 152 will be blocked by the adhesive. It is thus possible to improve the adhesion between the supporting portion and the vibrating plate without affecting the main-body fixing holes.
In the present preferred embodiment, the main- body fixing portions 161 and 162 are each positioned in the gap between adjacent blades. This configuration is preferable because the outer shape of the piezoelectric fan 10 is kept compact.
The main- body fixing portions 161 and 162 are preferably made of, for example, an insulating material such as glass epoxy resin. Thus, even when the piezoelectric fan 10 is secured with electrical conductors, such as metal screws, the electrical conductors and the vibrating plate 11 are electrically insulated by the main- body fixing portions 161 and 162. This makes it possible to easily realize a structure in which a desired voltage is externally applied to the vibrating plate.
A piezoelectric fan according to a second preferred embodiment of the present invention will be described with reference to FIGS. 4A-4C. FIG. 4A is an external perspective view of a piezoelectric fan 10A according to the second preferred embodiment of the present invention. FIG. 4B is a plan view of the piezoelectric fan 10A according to the second preferred embodiment of the present invention. FIG. 4C is a lateral view of the piezoelectric fan 10A according to the second preferred embodiment of the present invention.
The piezoelectric fan 10A of the second preferred embodiment preferably has the same configuration as that of the piezoelectric fan 10 of the first preferred embodiment, except that the piezoelectric fan 10A does not have the supporting body 141. The same effects as those in the first preferred embodiment are achieved in the second preferred embodiment.
A piezoelectric fan according to a third preferred embodiment of the present invention will be described with reference to FIGS. 5A-5C. FIG. 5A is an external perspective view of a piezoelectric fan 10B according to the third preferred embodiment of the present invention. FIG. 5B is a plan view of the piezoelectric fan 10B according to the third preferred embodiment of the present invention. FIG. 5C is a lateral view of the piezoelectric fan 10B according to the third preferred embodiment of the present invention.
The piezoelectric fan 10B of the third preferred embodiment includes a holder 14B, instead of the holder 14 of the first preferred embodiment. The other configuration is preferably the same as that of the first preferred embodiment. The following describes differences from the first preferred embodiment. The holder 14B includes a holding member 142B including main-body fixing portions 161B and 162B. The main-body fixing portions 161B and 162B are positioned on the side where the blades 111, 112, and 113 do not protrude from the base 110.
The shape and the arrangement of the main-body fixing portions are not limited to those in the preferred embodiments described above.
The number of blades included in the vibrating plate is not limited to that in the preferred embodiments described above.
Although the piezoelectric elements are preferably made of PZT ceramics in the preferred embodiments described above, the material of the piezoelectric elements is not limited to this. For example, the piezoelectric elements may be made of a piezoelectric material of lead-free piezoelectric ceramics, such as potassium-sodium niobate ceramics or alkali niobate ceramics.
Although the piezoelectric elements are preferably attached to both flat surfaces of the vibrating plate (bimorph type) in the preferred embodiments described above, the piezoelectric elements may be attached to one flat surface of the vibrating plate (unimorph type).
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Claims

1. (canceled)

2. A piezoelectric fan comprising:

a vibrating plate including a base having a flat plate shape and a plurality of blades arranged along the base at predetermined intervals in the longitudinal direction of the base;

a piezoelectric element attached to the blade; and

a holding member having a flat plate shape and including a supporting portion and a main-body fixing portion, the supporting portion being configured to support the base; wherein

adjacent ones of the plurality of blades are driven to vibrate in opposite phases; and

the main-body fixing portion of the holding member extends from the supporting portion and is arranged in a region which is not overlapped with the base in a plan view.

3. The piezoelectric fan according to claim 2, wherein the main-body fixing portion is positioned to a blade side compared with the base in the plan view of the vibrating plate.

4. The piezoelectric fan according to claim 2, wherein the holding member is made of an insulating material.

5. The piezoelectric fan according to claim 2, wherein the supporting portion has a shape that is identical or substantially identical to the base; and

the main-body fixing portion is positioned between the plurality of blades.

6. The piezoelectric fan according to claim 2, wherein the base and the plurality of blades are integrally configured and defined by a single unitary member.

7. The piezoelectric fan according to claim 2, wherein a width of each of plurality of blades varies along a length thereof.

8. The piezoelectric fan according to claim 2, wherein at least two piezoelectric elements are attached to opposite sides of each of the plurality of blades.

9. The piezoelectric fan according to claim 2, wherein the base and the plurality of blades are integrally configured and defined by a single unitary member.

10. The piezoelectric fan according to claim 2, wherein at least one piezoelectric element is attached to one side of each of the plurality of blades.

11. A piezoelectric fan comprising:

a vibrating plate including a base having a flat plate shape and including a plurality of blades connected to the base at predetermined intervals in the longitudinal direction of the base;

a piezoelectric element attached to the blade; and

a holding member having a flat plate shape and including a supporting portion having a shape that is identical or substantially identical to the base and a main-body fixing portion, the supporting portion being configured to support the base; wherein

the main-body fixing portion of the holding member extends from an end surface positioned between the plurality of blades and in parallel or substantially in parallel to the longitudinal direction of the supporting portion.

12. The piezoelectric fan according to claim 11, wherein the main-body fixing portion is positioned to a blade side compared with the base in the plan view of the vibrating plate.

13. The piezoelectric fan according to claim 11, wherein the holding member is made of an insulating material.

14. The piezoelectric fan according to claim 11, wherein the supporting portion has a shape that is identical or substantially identical to the base; and

the main-body fixing portion is positioned between the plurality of blades.

15. The piezoelectric fan according to claim 11, wherein the base and the plurality of blades are integrally configured and defined by a single unitary member.

16. The piezoelectric fan according to claim 11, wherein a width of each of plurality of blades varies along a length thereof.

17. The piezoelectric fan according to claim 11, wherein at least two piezoelectric elements are attached to opposite sides of each of the plurality of blades.

18. The piezoelectric fan according to claim 11, wherein the base and the plurality of blades are integrally configured and defined by a single unitary member.

19. The piezoelectric fan according to claim 11, wherein at least one piezoelectric element is attached to one side of each of the plurality of blades.