Piezoelectric blower

Abstract

A piezoelectric blower includes an outer casing and a blower main body. The outer casing houses the blower main body. The blower main body includes a top plate, side plate, first vibrating plate, piezoelectric element, intermediate plate, second vibrating plate, side plate, and bottom plate and has a structure in which they are laminated in sequence. The top plate, side plate, and first vibrating plate define a columnar first blower space. The second vibrating plate, side plate, bottom plate define a columnar second blower space. The distance from a neutral plane of the piezoelectric element in the thickness direction to a surface of the second vibrating plate, the surface being near the piezoelectric element, is longer than the distance from the neutral plane to a surface of the first vibrating plate, the surface being near the piezoelectric element.

Claims

1. A piezoelectric blower comprising: a piezoelectric element having a first principal surface and a second principal surface opposed to the first principal surface and including an electrode disposed on each of the first and second principal surfaces; a first vibrating plate bonded to the first principal surface of the piezoelectric element, the first vibrating plate being configured to be bent and vibrated by the piezoelectric element; a first casing bonded to a surface of the first vibrating plate opposite to the piezoelectric element, the first casing and the first vibrating plate defining a first blower space, the first casing having a first cavity communicating between the inside and outside of the first blower space; a second vibrating portion including an intermediate plate bonded to the second principal surface of the piezoelectric element and in contact with the electrode on the second principal surface and a flat plate portion connected to the intermediate plate, the second vibrating portion being configured to be bent and vibrated by the piezoelectric element; and a second casing bonded to a surface of the flat plate portion opposite to the piezoelectric element, the second casing and the second vibrating portion defining a second blower space, the second casing having a second cavity communicating between the inside and outside of the second blower space, the second casing and the flat plate portion of the second vibrating portion being distanced apart from the piezoelectric element, wherein both the first vibrating plate and the intermediate plate include a first principal surface and a second principal surface and each is conductive from the first principal surface to the second principal surface, and wherein an outer diameter of the piezoelectric element and an outer diameter of the intermediate plate are smaller than an outer diameter of the first vibrating plate and an outer diameter of the flat plate portion of the second vibrating portion such that the piezoelectric element bends and vibrates a central portion of the first vibrating plate and a central portion of the flat plate.

2. The piezoelectric blower according to claim 1, wherein the intermediate plate projects from the flat plate portion toward the piezoelectric element.

3. The piezoelectric blower according to claim 1, wherein the intermediate plate has a diameter smaller than a diameter of the second blower space.

4. The piezoelectric blower according to claim 1, wherein the intermediate plate and the flat plate portion in the second vibrating portion are integral with each other.

5. The piezoelectric blower according to claim 2, wherein the intermediate plate has a diameter smaller than a diameter of the second blower space.

6. The piezoelectric blower according to claim 2, wherein the intermediate plate and the flat plate portion in the second vibrating portion are integral with each other.

7. The piezoelectric blower according to claim 3, wherein the intermediate plate and the flat plate portion in the second vibrating portion are integral with each other.

8. The piezoelectric blower according to claim 1, further comprising an outer casing having an inner surface connected to peripheral edges of the first vibrating plate and the second vibrating portion.

9. The piezoelectric blower according to claim 8, further comprising key-shaped portions disposed between the inner surface of the outer casing and the peripheral edges of the first vibrating plate and the second vibrating portion, the key-shaped portions defining openings for allowing air to flow pass the first vibrating plate and the second vibrating portion.

10. The piezoelectric blower according to claim 9, wherein the key-shaped portions extend from the peripheral edges of the first vibrating plate and the second vibrating portion.

11. The piezoelectric blower according to claim 8, wherein the outer casing includes an opening for allowing fluid communication between a surrounding environment and an inner cavity of the outer casing.

12. The piezoelectric blower according to claim 11, wherein the opening is formed in a side wall of the outer casing.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 is an external perspective view of a piezoelectric blower 100 according to an embodiment of the present disclosure.

(2) FIG. 2 is a cross-sectional view of the piezoelectric blower 100 illustrated in FIG. 1 taken along line S-S.

(3) FIG. 3 is an exploded perspective view of a blower main body 101 included in the piezoelectric blower 100 illustrated in FIG. 1.

(4) FIGS. 4A and 4B are cross-sectional views of the piezoelectric blower 100 illustrated in FIG. 1 taken along the line S-S when it is driven so as to resonate at a frequency in first-order vibration mode (fundamental wave).

(5) FIG. 5 is a cross-sectional view of a piezoelectric blower 500 according to a first comparative example to the embodiment of the present disclosure.

(6) FIG. 6 is a cross-sectional view of a piezoelectric blower 600 according to a second comparative example to the embodiment of the present disclosure.

(7) FIG. 7 is a cross-sectional view of a piezoelectric blower 200 according to a first variation of the embodiment of the present disclosure.

(8) FIG. 8 is a cross-sectional view of a piezoelectric blower 300 according to a second variation of the embodiment of the present disclosure.

(9) FIG. 9 is a cross-sectional view of a piezoelectric blower 900 according to Patent Document 1.

DETAILED DESCRIPTION OF THE DISCLOSURE

Embodiments of Present Disclosure

(10) A piezoelectric blower 100 according to an embodiment of the present disclosure is described below.

(11) FIG. 1 is an external perspective view of the piezoelectric blower 100 according to the embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the piezoelectric blower 100 illustrated in FIG. 1 taken along line S-S. FIG. 3 is an exploded perspective view of a blower main body 101 included in the piezoelectric blower 100 illustrated in FIG. 1.

(12) The piezoelectric blower 100 includes an outer casing 17 and the blower main body 101.

(13) The outer casing 17 is cylindrical. The outer casing 17 has a plurality of intakes 53 in its side surface. The intakes 53 allow the air outside the outer casing 17 to be sucked into the outer casing 17 therethrough. The outer casing 17 has an exit 24 in its upper surface. The exit 24 allows the air inside the outer casing 17 to be ejected therethrough. The outer casing 17 has an exit 25 in its bottom surface. The exit 25 allows the air inside the outer casing 17 to be ejected therethrough. The outer casing 17 may be made of resin. The outer casing 17 houses the blower main body 101.

(14) The outer casing 17 used in the present embodiment is cylindrical. Other forms may also be used. The outer casing 17 may have a rectangular parallelepiped shape. The piezoelectric blower 100 may also be used in a state where the outer casing 17 is removed and only the blower main body 101 is disposed.

(15) The blower main body 101 includes a top plate 80, a side plate 70, a first vibrating plate 60, a piezoelectric element 40, an intermediate plate 190, a second vibrating plate 160, a side plate 170, and a bottom plate 180 disposed in this order from above and has a structure in which they are laminated in sequence. The top plate 80 and the side plate 70 form a first casing 110. The side plate 170 and the bottom plate 180 form a second casing 120. The top plate 80, the side plate 70, and the first vibrating plate 60 define a columnar first blower space 36. The second vibrating plate 160, the side plate 170, and the bottom plate 180 define a columnar second blower space 136.

(16) The first vibrating plate 60 corresponds to first vibrating portion in the present disclosure. The intermediate plate 190 and the second vibrating plate 160 form second vibrating portion in the present disclosure. The intermediate plate 190 corresponds to intermediate portion in the present disclosure. The second vibrating plate 160 corresponds to flat plate portion in the present disclosure.

(17) The top plate 80 has a disc shape. The top plate 80 has a first cavity 81 communicating between the inside and outside of the first blower space 36. The first cavity 81 is disposed in a location opposed to the exit 24 in the outer casing 17. The top plate 80 is bonded to an upper surface of the side plate 70.

(18) The side plate 70 has an annular shape. The side plate 70 is bonded to an upper surface of the first vibrating plate 60. Thus, the thickness of the side plate 70 is the height of the first blower space 36.

(19) The first vibrating plate 60 has a disc shape. The first vibrating plate 60 includes a disc portion 61, key-shaped supporting portions 62 horizontally projecting from the peripheral edge of the outer region of the disc portion 61 in a radial direction, and an outer terminal 63 for connecting to an external circuit.

(20) The piezoelectric element 40 has a disc shape and may be made of a PZT-based ceramic material. The piezoelectric element 40 has first and second principal surfaces 40A and 40B, each of which an electrode for driving the piezoelectric element 40 is disposed. The first principal surface 40A of the piezoelectric element 40 is bonded to the first vibrating plate 60. The second principal surface 40B of the piezoelectric element 40 is bonded to the intermediate plate 190.

(21) The intermediate plate 190 has a disc shape. The intermediate plate 190 is bonded to an upper surface 160A of the second vibrating plate 160. The diameter L1 of the intermediate plate 190 is smaller than the diameter L2 of the second blower space 136.

(22) The second vibrating plate 160 has a disc shape. The second vibrating plate 160 includes a disc portion 161, key-shaped supporting portions 162 horizontally projecting from the peripheral edge of the outer region of the disc portion 161 in a radial direction, and an outer terminal 163 for connecting to an external circuit. The second vibrating plate 160 is bonded to an upper surface of the side plate 170.

(23) The side plate 170 has an annular shape. The side plate 170 is bonded to an upper surface of the bottom plate 180. Thus, the thickness of the side plate 170 is the height of the second blower space 136.

(24) The bottom plate 180 has a disc shape. The bottom plate 180 has a second cavity 181 communicating between the inside and outside of the second blower space 136. The second cavity 181 is disposed in a location opposed to the exit 25 in the outer casing 17.

(25) Example materials and dimensions of the components included in the blower main body 101 in the present embodiment are described below. A metal material may be one example of the material of each of the top plate 80, side plate 70, first vibrating plate 60, intermediate plate 190, second vibrating plate 160, side plate 170, and bottom plate 180. In the present embodiment, SUS430 is used as the material of each of the top plate 80, side plate 70, first vibrating plate 60, second vibrating plate 160, side plate 170, and bottom plate 180, and 42Ni is used as the material of the intermediate plate 190.

(26) The dimensions of the top plate 80 are 17 mm in outside diameter, 1 mm in inside diameter, and 0.5 mm in thickness. The dimensions of the side plate 70 are 17 mm in outside diameter, 14 mm in inside diameter, and 0.3 mm in thickness. The dimensions of the first vibrating plate 60 are 17 mm in diameter and 0.4 mm in thickness. The dimensions of the piezoelectric element 40 are 11 mm in diameter and 0.1 mm in thickness. The dimensions of the intermediate plate 190 are 4 mm in diameter and 0.2 mm in thickness. The dimensions of the second vibrating plate 160 are 17 mm in diameter and 0.4 mm in thickness. The dimensions of the side plate 170 are 17 mm in outside diameter, 14 mm in inside diameter, and 0.3 mm in thickness. The dimensions of the bottom plate 180 are 17 mm in outside diameter, 1 mm in inside diameter, and 0.5 mm in thickness.

(27) In the above-described configuration, the blower main body 101 is elastically supported on the outer casing 17 by the four supporting portions 62 in the first vibrating plate 60 and the four supporting portions 162 in the second vibrating plate 160. As illustrated in FIG. 2, an airway 31 is disposed between the first casing, which is the bonded structure of the top plate 80 and the side plate 70, and the outer casing 17. An airway 131 is disposed between the second casing, which is the bonded structure of the bottom plate 180 and the side plate 170, and the outer casing 17.

(28) As illustrated in FIG. 2, the distance K2 from a neutral plane C in the piezoelectric element 40 in the thickness direction to the upper surface 160A, which is near the piezoelectric element 40, of the second vibrating plate 160 is longer than the distance K1 from the neutral plane C in the piezoelectric element 40 in the thickness direction to a surface 60B of the first vibrating plate 60, the surface 60B facing the piezoelectric element 40, by the thickness of the intermediate plate 190. The neutral plane C in the piezoelectric element 40 in the thickness direction is a plane that is perpendicular to the thickness direction of the piezoelectric element 40 and that extends along the center of the piezoelectric element 40 in the thickness direction.

(29) The piezoelectric element 40 is disposed between the first vibrating plate 60 and the intermediate plate 190, both of which have conductivity. The electrode on the first principal surface 40A of the piezoelectric element 40 is bonded to the lower surface 60B, which is opposite to the first blower space 36, of the first vibrating plate 60. The electrode on the second principal surface 40B of the piezoelectric element 40 is bonded to an upper surface 190A of the intermediate plate 190, the upper surface 190A facing the first blower space 36. Thus, the piezoelectric element 40 expands and contracts in accordance with an alternating drive voltage applied across both the electrodes from the outer terminals 63 and 163.

(30) The piezoelectric blower 100 is arranged such that the exit 24 faces a first cooling target (heat source), such as a central processing unit (CPU), and the exit 25 faces a second cooling target. The piezoelectric blower 100 cools both of the first and second cooling targets at the same time by air flowing out through the exits 24 and 25.

(31) Air streams occurring when the piezoelectric blower 100 is operating are described below.

(32) FIGS. 4A and 4B are cross-sectional views of the piezoelectric blower 100 illustrated in FIG. 1 taken along the line S-S when the piezoelectric blower 100 is driven so as to resonate at a frequency in first-order vibration mode (fundamental wave) of the blower main body. The arrows in the drawings denote the streams of air.

(33) In the state illustrated in FIG. 3, when an alternating drive voltage corresponding to a frequency in first-order vibration mode (fundamental wave) of the blower main body is applied to the piezoelectric element 40 from the outer terminals 63 and 163, each of the first and second vibrating plates 60 and 160 bends and vibrates concentrically.

(34) At the same time, due to the pressure changes in the first blower space 36 resulting from the bending vibration of the first vibrating plate 60, the top plate 80 bends and vibrates concentrically together with the bending vibration of the first vibrating plate 60 (in the present embodiment, such that its vibration phase lags by 180 degrees). Thus, as illustrated in FIGS. 4A and 4B, the first vibrating plate 60 and the top plate 80 bend and deform, and the volume of the first blower space 36 changes periodically.

(35) At the same time, due to the pressure changes in the second blower space 136 resulting from the bending vibration of the second vibrating plate 160, the bottom plate 180 bends and vibrates concentrically together with the bending vibration of the second vibrating plate 160 (in the present embodiment, such that its vibration phase lags by 180 degrees). Thus, as illustrated in FIGS. 4A and 4B, the second vibrating plate 160 and the bottom plate 180 bend and deform, and the volume of the second blower space 136 changes periodically.

(36) First, the air streams in the first blower space 36 are described.

(37) As illustrated in FIG. 4A, when an alternating drive voltage is applied to the piezoelectric element 40 and the first vibrating plate 60 bends toward the piezoelectric element 40, the volume of the first blower space 36 increases. With this, air outside the piezoelectric blower 100 is sucked into the first blower space 36 through the intakes 53, airway 31, and first cavity 81. At this time, although no air flows out of the first blower space 36, there is inertial force of air streams from the exit 24 to the outside of the piezoelectric blower 100.

(38) As illustrated in FIG. 4B, when an alternating drive voltage is applied to the piezoelectric element 40 and the first vibrating plate 60 bends toward the first blower space 36, the volume of the first blower space 36 decreases. With this, the air inside the first blower space 36 is discharged through the first cavity 81, passes through the airway 31, and is ejected through the exit 24.

(39) At this time, due to the air discharged from the first blower space 36, the air outside the piezoelectric blower 100 is drawn through the intakes 53 and the airway 31 and then ejected through the exit 24. Thus the quantity of flow of air ejected through the exit 24 increases by the quantity of flow of air drawn from the outside.

(40) Next, the air streams in the second blower space 136 are described.

(41) As illustrated in FIG. 4B, when an alternating drive voltage is applied to the piezoelectric element 40 and the intermediate plate 190 and the second vibrating plate 160 bend toward the piezoelectric element 40, the volume of the second blower space 136 increases. With this, air outside the piezoelectric blower 100 is sucked into the second blower space 136 through the intakes 53, airway 131, and second cavity 181. At this time, although no air flows out of the second blower space 136, there is inertial force of air streams from the exit 25 to the outside of the piezoelectric blower 100.

(42) As illustrated in FIG. 4A, when an alternating drive voltage is applied to the piezoelectric element 40 and the intermediate plate 190 and the second vibrating plate 160 bend toward the second blower space 136, the volume of the second blower space 136 decreases. With this, the air inside the second blower space 136 is discharged through the second cavity 181, passes through the airway 131, and is ejected through the exit 25.

(43) At this time, due to the air discharged from the second blower space 136, the air outside the piezoelectric blower 100 is drawn through the intakes 53 and the airway 131 and then ejected through the exit 25. Thus the quantity of flow of air ejected through the exit 25 increases by the quantity of flow of air drawn from the outside.

(44) As illustrated in FIG. 2, the distance K2 from the neutral plane C in the piezoelectric element 40 in the thickness direction to the upper surface 160A, which is near the piezoelectric element 40, of the second vibrating plate 160, is longer than the distance K1 from the neutral plane C in the piezoelectric element 40 in the thickness direction to the surface 60B, which is near the piezoelectric element 40, of the first vibrating plate 60, by the thickness of the intermediate plate 190. The neutral plane C in the piezoelectric element 40 in the thickness direction is a plane that is perpendicular to the thickness direction of the piezoelectric element 40 and that extends along the center of the piezoelectric element 40 in the thickness direction. Thus the blower main body 101 is asymmetric with respect to the neutral plane C.

(45) Here, a force caused by the expansion and contraction of the piezoelectric element 40 is expressed as F. The flexibility of the first vibrating plate 60 is expressed as moment M1. The flexibility of the second vibrating plate 160 is expressed as moment M2.

(46) When the piezoelectric element 40 contracts, the moment M1=F K1 in the direction in which the first vibrating plate 60 flexes toward the first blower space 36 occurs in the first vibrating plate 60, and the moment M2=F K2 in the direction in which the second vibrating plate 160 flexes toward the second blower space 136 occurs in the second vibrating plate 160. The moments M1 and M2 are in the opposite directions. The first vibrating plate 60 and the second vibrating plate 160 are bonded to the piezoelectric element 40 and the intermediate plate 190, respectively. Thus, when the piezoelectric element 40 contracts, the moment M2M1 in the direction in which both the vibrating plates 60 and 160 flex toward the second blower space 136 occurs in both the vibrating plates 60 and 160.

(47) Here, when M1 and M2 are near values, the moments M1 and M2 are cancelled out, and the moment M2M1 occurring in both the vibrating plates 60 and 160 is small. Thus, large flexural deformation does not occur in both the vibrating plates 60 and 160.

(48) As illustrated in FIG. 2, however, when K2 is larger than K1, the moment M2M1 in the direction in which both the vibrating plates 60 and 160 flex toward the second blower space 136 is large. Thus, large flexural deformation toward the second blower space 136 occurs in both the vibrating plates 60 and 160.

(49) In contrast, when the piezoelectric element 40 expands, the direction of the moments M1 and M2 is opposite to the direction described above. That is, when the piezoelectric element 40 expands, the moment M2M1 in the direction in which both the vibrating plates 60 and 160 flex toward the first blower space 36 occurs in both the vibrating plates 60 and 160.

(50) When M1 and M2 are near values, the moments M1 and M2 are cancelled out, and the moment M2M1 occurring in both the vibrating plates 60 and 160 is small. Thus, large flexural deformation does not occur in both the vibrating plates 60 and 160.

(51) As illustrated in FIG. 2, however, when K2 is larger than K1, the moment M2M1 in the direction in which both the vibrating plates 60 and 160 flex toward the first blower space 36 is large. Thus, large flexural deformation toward the first blower space 36 occurs in both the vibrating plates 60 and 160.

(52) In this manner, the expansion and contraction of the piezoelectric element 40 causes both the first and second vibrating plates 60 and 160 to flexurally vibrate without cancelling out their vibrations produced by the piezoelectric element 40. That is, the expansion and contraction of the piezoelectric element 40 changes the volume of each of the first and second blower spaces 36 and 136. Thus, the sum of the volume change amount of the first blower space 36 and that of the second blower space 136 is larger than the volume change amount of only one blower space in the related art. Accordingly, the discharge flow quantity in the blower main body 101 is larger than that in the related art.

(53) In the blower main body 101, the first principal surface 40A of the piezoelectric element 40 is in contact with the conductive first vibrating plate 60, and the second principal surface 40B is in contact with the conductive intermediate plate 190. That is, the contact between the electrode on each of both the principal surfaces 40A and 40B of the piezoelectric element 40 and the wire connected to the electrode is surface contact. Thus, in the blower main body 101, the connection between the electrode on each of both the principal surfaces 40A and 40B of the piezoelectric element 40 and the wire connected to the electrode is stronger than that in the related art.

(54) Accordingly, the piezoelectric blower 100 in the present embodiment can have a discharge flow quantity larger than that in the related art and can have connection with the electrode on each of both the principal surfaces 40A and 40B of the piezoelectric element 40 stronger than that in the related art.

(55) The comparison between the discharge flow quantity in the blower main body 101 illustrated in FIGS. 2 and 3 and the discharge flow quantity in a blower main body 501 in a piezoelectric blower 500 according to a first comparative example to the embodiment in the present disclosure is described below.

(56) FIG. 5 is a cross-sectional view of the piezoelectric blower 500 according to the first comparative example to the embodiment in the present disclosure. The piezoelectric blower 500 differs from the piezoelectric blower 100 in that the intermediate plate 190, second vibrating plate 160, side plate 170, bottom plate 180, and outer casing 17 are not included. Specifically, the blower main body 501 in the piezoelectric blower 500 includes the top plate 80, side plate 70, first vibrating plate 60, and piezoelectric element 40 in this order from above and has a structure in which they are laminated in sequence. The other configuration of the blower main body 501 is the same as that of the blower main body 101 and is not described here.

(57) The following illustrates the results obtained from the simulated calculation of the displacement amount of the center of each of the blower main bodies 101 and 501 and the volume change amount of the blower space when a sinusoidal alternating drive voltage of 15 Vpp corresponding to the frequency in first-order vibration mode (fundamental wave) of the blower main bodies 101 and 501 is applied to the blower main bodies 101 and 501.

(58) The discharge flow quantity in the blower main body 101 is the sum of the quantity of flow of air discharged through the first cavity 81 and that through the second cavity 181. The discharge flow quantity in the blower main body 501 is the quantity of flow of air discharged through the first cavity 81. In the experiment, for the blower main body 101 with the outer casing 17 being detached, the displacement of the center of the first vibrating plate 60 and the sum of the volume change amount of the first blower space 36 and that of the second blower space 136 were calculated.

(59) The experiment reveals that the displacement of the center of the first vibrating plate 60 in the blower main body 501 is 5.8 m and that in the blower main body 101 is 3.3 m. The experiment reveals that the volume change amount of the first blower space 36 in the blower main body 501 is 1.19 L/min and the sum of the volume change amount of the first blower space 36 and that of the second blower space 136 in the blower main body 101 is 1.61 L/min.

(60) It is expected from the above results that, because the discharge flow quantity in the blower main body is proportional to the volume change amount of the blower space, the discharge flow quantity in the blower main body 101 is significantly larger than the discharge flow quantity in the blower main body 501. The reasons for the above results may be that the blower main body 101 includes the two blower spaces 36 and 136, the flexibility of the first vibrating plate 60 and that of the second vibrating plate 160 are different because the distances K1 and K2 are different as described above, and both the first and second vibrating plates 60 and 160 flexurally vibrate without cancelling out their vibrations produced by the piezoelectric element 40.

(61) Accordingly, the blower main body 101 in the present embodiment can have a discharge flow quantity larger than that in a blower main body in the related art.

(62) Next, the comparison between the discharge flow quantity in the blower main body 101 illustrated in FIGS. 2 and 3 and the discharge flow quantity in a blower main body 601 in a piezoelectric blower 600 according to a second comparative example to the embodiment in the present disclosure is described below.

(63) FIG. 6 is a cross-sectional view of the piezoelectric blower 600 according to the second comparative example to the embodiment in the present disclosure. The piezoelectric blower 600 differs from the piezoelectric blower 100 in that the intermediate plate 190 and outer casing 17 are not included and a first vibrating plate 660 is included.

(64) Specifically, the blower main body 601 in the piezoelectric blower 600 includes the top plate 80, side plate 70, first vibrating plate 660, piezoelectric element 40, second vibrating plate 160, side plate 170, and bottom plate 180 in this order from above and has a structure in which they are laminated in sequence. The first vibrating plate 660 includes an intermediate portion 690. The diameter L1 of the intermediate portion 690 is larger than the diameter L2 of the first blower space 36. The first vibrating plate 660 is thicker than the second vibrating plate 160 by the thickness of the intermediate portion 690. Thus, the distance K1 from the neutral plane C in the piezoelectric element 40 in the thickness direction to a surface 660B of the first vibrating plate 660, the surface 660B facing the piezoelectric element 40, is equal to the distance K2 from the neutral plane C in the piezoelectric element 40 in the thickness direction to the surface 160A, which is near the piezoelectric element 40, of the second vibrating plate 160. The other configuration of the blower main body 601 is the same as that of the blower main body 101 and is not described here.

(65) In the second variation, the dimensions of the first vibrating plate 660 are 17 mm in diameter and 0.4 mm in thickness. The dimensions of the second vibrating plate 160 are 17 mm in diameter and 0.2 mm in thickness. The materials and dimensions of the other components are the same as those in the blower main body 101.

(66) Below are results obtained from calculation of simulation of the amount of displacement of the center of each of the blower main bodies 101 and 601 and the volume change amount of the blower space when a sinusoidal alternating drive voltage of 15 Vpp corresponding to the frequency in first-order vibration mode (fundamental wave) of the blower main bodies 101 and 601 is applied to the blower main bodies 101 and 601.

(67) The discharge flow quantity in the blower main body 101 is the sum of the quantity of flow of air discharged through the first cavity 81 and that through the second cavity 181. The discharge flow quantity in the blower main body 601 is the sum of the quantity of flow of air discharged through the first cavity 81 and that through the second cavity 181. In the experiment, for the blower main body 101 with the outer casing 17 being detached, the displacement of the center of the first vibrating plate 60 and the sum of the volume change amount of the first blower space 36 and that of the second blower space 136 were calculated.

(68) The experiment reveals that the displacement of the center of the first vibrating plate 660 in the blower main body 601 is 0.7 m and that of the first vibrating plate 60 in the blower main body 101 is 3.3 m. The experiment reveals that the sum of the volume change amount of the first blower space 36 and that of the second blower space 136 in the blower main body 601 is 0.52 L/min and that in the blower main body 101 is 1.61 L/min.

(69) It is expected from the above results that, because the discharge flow quantity in the blower main body is proportional to the volume change amount of the blower space, the discharge flow quantity in the blower main body 101 is significantly larger than the discharge flow quantity in the blower main body 601.

(70) The reasons for the above results for the blower main body 601 may be that, as illustrated in FIG. 6, the diameter L1 of the intermediate portion 690 is larger than the diameter L2 of the second blower space 136, the distance K1 and the distance K2 are the same, thus the flexibility of the first vibrating plate 660 and that of the second vibrating plate 160 are substantially the same, and the vibration of the first vibrating plate 660 and the vibration of the second vibrating plate 160 are cancelled out.

(71) The reasons for the above results for the blower main body 101 may be that, as illustrated in FIG. 2, the diameter L1 of the intermediate plate 190 is smaller than the diameter L2 of the second blower space 136, the distance K2 is longer than the distance K1, thus the flexibility of the first vibrating plate 60 and that of the second vibrating plate 160 are different, and large flexural deformation caused by the expansion and contraction of the piezoelectric element 40 occurs in both vibrating plates 60 and 160.

(72) Accordingly, the blower main body 101 according to the present embodiment can have a discharge flow quantity larger than that in a blower main body in the related art.

Other Embodiments

(73) In the above embodiment, as illustrated in FIG. 2, the intermediate plate 190 and the second vibrating plate 160 are disposed as separated components. Other forms may also be used. For example, as illustrated in FIG. 7, an intermediate portion 290 and the second vibrating plate 160 may be integrally formed of the same material. In this case, the intermediate portion 290 and the second vibrating plate 160 form second vibrating portion in the present disclosure.

(74) In a piezoelectric blower 200 illustrated in FIG. 7, as similar to the above, the distance K2 from the neutral plane C in the piezoelectric element 40 in the thickness direction to a surface 260A of the second vibrating plate 160, the surface 260A facing the piezoelectric element 40, is longer than the distance K1 from the neutral plane C to the surface 60B, which is near the piezoelectric element 40, of the first vibrating plate 60 by the thickness of the intermediate portion 290. Accordingly, the piezoelectric blower 200 can achieve substantially the same advantages as in the piezoelectric blower 100.

(75) Additionally, because the intermediate portion 290 and the second vibrating plate 160 in the piezoelectric blower 200 are integrally formed of the same material, the strength of bonding between the intermediate portion 290 and the second vibrating plate 160 is large. Thus, this configuration can prevent a decrease in characteristics of the piezoelectric blower 200 caused by misalignment between the intermediate portion 290 and the second vibrating plate 160, for example. Accordingly, this configuration can achieve improved reliability of the piezoelectric blower 200.

(76) In the above embodiment, as illustrated in FIG. 2, the piezoelectric element 40 is directly bonded to the first vibrating plate 60. Other forms may also be used. For example, as illustrated in FIG. 8, an intermediate plate 395 may be disposed between the piezoelectric element 40 and the first vibrating plate 60. In this case, the bonded structure of the first vibrating plate 60 and the intermediate plate 395 corresponds to first vibrating portion in the present disclosure. In this case, the distance K1 is determined with reference to a surface 395B of the intermediate plate 395, the surface 395B being near the piezoelectric element 40.

(77) In a piezoelectric blower 300 illustrated in FIG. 8, as similar to the above, the distance K2 from the neutral plane C in the piezoelectric element 40 in the thickness direction to the surface 160A, which is near the piezoelectric element 40, of the second vibrating plate 160 is longer than the distance K1 from the neutral plane C to the surface 395B, which is near the piezoelectric element 40, of the intermediate plate 395 by the thickness of the intermediate plate 190. Accordingly, the piezoelectric blower 300 can achieve substantially the same advantages as in the piezoelectric blower 100.

(78) In the above embodiment, air is used as the gas. Other forms may also be used. Gases other than air may also be applicable.

(79) In the above embodiment, the piezoelectric element 40 is made of a PZT-based ceramic material. Other forms may also be used. For example, the piezoelectric element 40 may be made of lead-free piezoelectric ceramic materials, such as a potassium sodium niobate-based ceramic material and an alkali niobate-based ceramic material.

(80) In the above embodiment, the disc-shaped piezoelectric element 40 is used. Other forms may also be used. For example, the piezoelectric element 40 may have a rectangular plate shape, a polygonal plate shape, or an elliptic plate shape.

(81) In the above embodiment, the disc-shaped first and second vibrating plates 60 and 160, the disc-shaped intermediate plate 190, the disc-shaped bottom plate 180, and the disc-shaped top plate 80 are used. Other forms may also be used. For example, these components may have a rectangular plate shape, a polygonal plate shape, or an elliptic plate shape.

(82) In the above embodiment, each piezoelectric blower is driven so as to resonate at the frequency in first-order vibration mode (fundamental wave) of the blower main body. Other forms may also be used. In implementation, it may be driven so as to resonate at a frequency in odd-order vibration mode having a plurality of node at or above the third-order vibration mode.

(83) The above embodiment illustrates an example in which the top plate 80 bends and vibrates concentrically together with the bending vibration of the first vibrating plate 60. Other forms may also be used. In implementation, only the first vibrating plate 60 may bend and vibrate, and the top plate 80 may not bend or vibrate together with the bending vibration of the first vibrating plate 60.

(84) The above embodiment illustrates an example in which the bottom plate 180 bends and vibrates concentrically together with the bending vibration of the second vibrating plate 160. Other forms may also be used. In implementation, only the second vibrating plate 160 may bend and vibrate, and the bottom plate 180 may not bend or vibrate together with the bending vibration of the second vibrating plate 160.

(85) Lastly, the description of the above embodiments is to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is indicated by the appended claims rather than by the foregoing embodiments. All changes that come within the meaning and range of equivalency of the claims are to be embraced within the scope of the disclosure.

(86) C neutral plane

(87) 1 inner casing

(88) 3 blower space

(89) 4 supporting portion

(90) 5 outer casing

(91) 6 airway

(92) 8 second vent

(93) 10 plate portion

(94) 11 first vent

(95) 13 frame plate portion

(96) 17 outer casing

(97) 20 piezoelectric element

(98) 21 diaphragm

(99) 22 intermediate plate

(100) 24 exit

(101) 25 exit

(102) 31 airway

(103) 36 first blower space

(104) 40 piezoelectric element

(105) 53 intake

(106) 60 first vibrating plate

(107) 61 disc portion

(108) 62 supporting portion

(109) 63, 163 outer terminal

(110) 70 side plate

(111) 79 lead wire

(112) 80 top plate

(113) 81 first cavity

(114) 82, 83 electrode terminal

(115) 100 piezoelectric blower

(116) 101 blower main body

(117) 110 first casing

(118) 120 second casing

(119) 131 airway

(120) 136 second blower space

(121) 160 second vibrating plate

(122) 161 disc portion

(123) 162 supporting portion 170 side plate

(124) 180 bottom plate

(125) 181 second cavity

(126) 190 intermediate plate

(127) 200 piezoelectric blower

(128) 300 piezoelectric blower

(129) 395 intermediate plate

(130) 500 piezoelectric blower

(131) 501 blower main body

(132) 600 piezoelectric blower

(133) 601 blower main body

(134) 660 first vibrating plate

(135) 900 piezoelectric blower