US3836794A - Piezoelectric transformers - Google Patents

Abstract

In a piezoelectric transformer comprising an elongated ceramic body with one-half polarized in the direction of the thickness and the remaining half polarized in the longitudinal direction, a pair of input electrodes applied to the first half and an output electrode applied to the outer end of the second half, the input electrodes are comprised by electroconductive rubber covering substantially the entire surface of the first half and the output electrode is comprised by electroconductive rubber fitted over the outer end of the second half.

Description

United States Patent 91 Shimizu et a1.

[451 Sept. 17, 1974 1 PIEZOELECTRIC TRANSFORMERS [75] Inventors: MasaoShimizu, Tokyo; Yasunoeu Sakurai, Kawasaki; Hideo Sato, Tokyo; Keiji lnoue, Yokohama, all of Japan [73] Assignee: Denki Onkyo Company Limited, Tokyo, Japan [22] Filed: July 23, 1970 [21] Appl. No.: 57,462

[30] Foreign Application Priority Data Sept. 9, 1969 Japan 44-253mm Sept. 9, 1969 Japan 44-8S305[U] Sept. 9, 1969 Japan 44-85306[U] Sept. 9, 1969 Japan 44-85308[U] Aug. 1, 1969 Japan 44-72864[U] [52] US. Cl 3l0/9.7, 310/82, 310/91,

[51] Int. Cl .L H041 17/00 [58] Field of Search 310/82, 8.5, 8.9, 9.1-9.4

[56] References Cited UNITED STATES PATENTS 2,955,216 10/1960 Dieter et a1 310/94 2,975,354 3/1961 Rosen 333/72 3,179,826 4/1965 Trott et a1 310/82 3,313,891 4/1967 Wood 310/9.1 X 3,453,458 7/1969 Curran et a1 310/91 3,475,565 10/1969 Collins et a1 310/8.5 X 3,495,103 2/1970 Nakajima 310/9.1

3,518,470 6/1970 Lungo 310/89 X 3,560,772 2/1971 Lungo et a1 310/9.8 X

3,562,792 2/1971 Berlincourt 310/8.1

' 3,564,764 2/1971 Fujishima 310/94 3,586,889 Kolter 310/8.4

Primary Examiner-Mark O. Budd Attorney, Agent, or Firm-Dike, Bronstein, Roberts, Cushman & Pfund [5 7 ABSTRACT In a piezoelectric transformer comprising an elongated ceramic body with one-half polarized in the direction of the thickness and the remaining half polarized in the longitudinal direction, a pair of input electrodes applied to the first half and an output electrode applied to the outer end of the second half, the input electrodes are comprised by electroconductive rubber covering substantially the entire surface of the first half and the output electrode is comprised by electroconductive rubber fitted over the outer end of the second half.

6 Claims, 8 Drawing Figures PATENTEDSEPI 11am 3.886.794 sum 1 or 2 160 High l gG Current A V 53 0 mooso :Q

INVENTOR E MASAO SHIMIZU YASUNOBU SAKURAI HIDEO SATO KEIJI INOUE 4 ATToRA/EY m mmszmlan 3.836.794 I sum 2 0F 2 INVENTOR. 5

MASAO SHIMIZU YASUNOBU SAKURAI HIDEO SATO KEIJI INOUE M, M$ l ATToRNEY I b i dl 9 r. ber vin a r si tivi .Qf the a si 9 .2+ 9 1mm an on inin rspne wi whe n t ed. i h

1 PIEzonL cr c" TRA sro Ens BACKGROUND QF-THEI INVENTION Thisinvention relateslto. a piezoelectric.transducer, 5

area of the driving portion of the ceramic body. Each electrode plate is provided with a stern extending in the i longitudinal direction of the electrodeplate, said stem more particularly to a piezoelectric transformer having novel, electrode construction.

As is well known in the art thepiezoelectric transformer generally comprises an elongated rectangular ceramic bodylof .bariurntitanate (BaTiO or l ead zirconate titanate or I like. One-half the length, of the ceramic body, that is the driving portion is polarized in the direction of thickness. while theremaining half;

i.el, the generating portion is polarized in the direction of length. Apair ofinputlelectrodes of silverfor example is'applied by [f ring f on the opposite surfaces of. the

d n p n gn and an 'u m l c rod isisecn ed by firin rt -6n v S rf th ssberat n nirfin- L ad wires are soldered .to the fpaii ofinput electrodes and tn b ith {a gimme" that s s l ic int ar d st oy d .tqdamas he e sc ds urfaces and tha t h ljadwi s ar -broken A houg the leadiwires maybe bonded tothe electrodes-by lizing asuitable such bondings-areoften loos,- ened or'disenga edduringslight elongation and com traction of the ramic bodyldiie tot h he du n he seme 9f th -i i zqeld i a s .For this reason, use of the binder is not advantageous.

SUMMARY OF THE INVENTIQN these m ria j t l i kampi ng:plates'a s p b ided wit i longitudinal grooves or openings toaccommodateend portions of the lead wires.

Further, according to this invention the driving electrodes may comprise a pair of electrode plates of conductive rubber covering substantially the entiresurface serving toreoeive alead wire forexternal connection.

Further, the stem may take the form of a projection on the upper surface of the electrodeplate. According to ,anotherjfeature of i this invention, the electrode, plates areurged against the surfaceof the ceramiobodyby meansofa pair ofv opposing stays on both sides of the ceramic body and a pair of supporting rods of.elastic v electroconductive rubber. Theerids of. these supporting ,rods are, firmly clamped. by, the. stays; s o.thatthe rods-are urged against the electrode plates.

BRlEF DESCRIPTION OF THE DRAWINGS Theinvention canvbemore fully understood-from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a-p'erspective view of one (embodiment of the novelpiezoelectric transformer;

I FIG. 2 is a sectional view of a portion of the piezoefl eetric transformer, takenalonga-lirie 2 2;

amodified piezoelectric transformer;

F1 G. 4 shows characteristic curves showing the relatiens pb twc igh o tag iir lent n h g o ta outputlof a conventional piezoelectric transformer and =FIG 3-is a sectional view c'orr'espondingto FIG; 2 of ,o th w p e oe ect i ra o mer;

5 shows another modified piezoelectric transforr ner,

l6, 6 shows still another modifieation of this invention; 7 is a perspective viewof modified electrode plates utilized in the piezoelectric transformer shown in G" an F IG 8 is a perspective view of yetan'other embodiment of this invention.

DESCRIPTIQN or THE PREFERRED EMBQDIMENTS R fin ng now to he comp ny na wi g t e piezoel ct i t n me hown in FIGS- 1 n 2 comp ises a tan u ar Pl t p d ce am ody 16 ing one-half, that is driving portion 12, polarized in the dir ction of thickness and the Oil- .1 half; that is the generating portion 14, polarized in the axial direction. Q s te ace-89f the drivins or o' 2 ar o e ed by' silver electrode layers 18 and 20 shown exagger V a one @331 22a and 2 4 IG- of e ch f i s} 1 M62 n 2 d p e t ns er y of t e cierami'c bo 'y- These d p n P t s a emade'qf a e as tio'insulating material such as natural or synthetic rubher and their inner surfaces are provided with grooves 3 an 1 9 acs mmod t t e ends. 22a an of input" leadwi es 221111 124, pposit endthe clamp.- in'g plates 2 and 2 a e firml W teri to the cerami body by means; of apair of U-shaped olamps' fland- 36'.

Advantageously, clamps 34 and 36 are molded from elastic insulative synthetic resinous material or made of spring metal strips covered by insulating coatings. In the case of a piezoelectric transformer operating at a A mode, it is preferable to locate the clamps 26 and 28 1/4 spaced apart from the left hand end of the ceramic body, where 1 represents the total length of the ceramic body. These positions, that is the intermediate points along the length of the driving portion, correspond to the nodes of the mechanical oscillation of the ceramic body and do not vibrate substantially so that application of additional weight on the ceramic body does not affect in any way the natural frequency of the ceramic body as well as its oscillation characteristics.

On the outer end of the right hand half or the generating portion of the ceramic body 16 is provided a cap shaped output electrode 40 of electroconductive rubber having a rectangular recess 38 corresponding to the cross-sectional configuration of the generating portion. The output electrode 40 can also be formed in the form of a conductive band and is formed with a laterally extending thin stem 42. The outer end of this stem 42 is connected toone end of a selenium rectifier 46 supported by a stationary arm 44, as shown in FIG. 1. Alternatively, as shown in FIG. 5, one end of an output lead wire 48 may be firmly wound about the outer end of the stem 42.

FIG. 3 shows a modified configuration of the clamping plates, wherein clamping plates 49 and 50 are molded from conductive rubber and are provided with longitudinal narrow openings 52 and 54 near the center threof to snugly receive end portions 22a and 24a of input lead wires 22 and 24.

As can be clearly noted from foregoing description according to the novel electrode constructions shown in FIGS. 1 to 3 the lead wires are more firmly secured to the electrode layers than the prior art electrode construction so that lead wires would never be loosened or disengaged by the vibration of the ceramic body 16. Further, since according to this invention lead wires are elastically clamped by clamping plates made of elastic material such as rubber, vibrations transmitted to lead wires are efficiently absorbed thus protecting them against breakage.

FIG. 4 shows comparison of high voltage current viz high output voltage characteristics of a prior art transformer (curve b) and of the novel piezoelectric transformer (curve a). Characteristic curve a shown in FIG. 4 was obtained from a piezoelectric transformer operating at the )t/Z mode and provided with the electrode construction shown in FIG. 1. As can be noted from this curve, although clamping plates 26 and 28 are not located at the nodal point of the vibration of the ceramic body 16, the high output values are not varied appreciably showing only 5 percent decrease when compared with the prior art piezoelectric transformer.

FIG. 5 illustrates a modified clamping device 56 different from that shown in FIGS. 1 and 2. Clamping device 56 comprises rigid insulator members 58 and 60 of I synthetic resin such as formaldehyde resin, epoxide to clamping plates 26 and '28 (in the case of FIG. 3, clamping plates 49 and 50) is mounted at a point l/4 separated from the left hand end of the ceramic body or at the nodal point of the vibration of the ceramic body operating at thek mode. Although not shown in the drawing the clamping device 56 urging clamping plates 26 and 28 or 49 and 50 against the ceramic body is suitably mounted on. the; stationary portion to support the ceramic body. v I

FIG. 6 shows a modified embodiment of this invention wherein above described clamping plates 26, 28 or 49, 50 are replaced by a pair of electrode plates and 72 of electroconductive rubber and covering substantially the entire surface of the driving portion 12 of the ceramic body 16. One side of each of electrode plates 70 and 72 is provided with narrow integral stems or extensions 74 and 76 extending in the longitudinal direction of the ceramic body. End portions 22a and 24a of input lead wires 22 and 24 are firmly wrapped about free ends of stems 74 and 76. Alternatively, the outer ends of the stems may be securely fixed to the stationary portion.

In a modified electrode plate 70 shown in FIG. 7 a projection 78 is formed on the upper surface thereof and the input lead wire is connected to the projection 78. The modifications shown in FIGS. 6 and 7 eliminate silver electrode layers 18 and 20, but if required such electrode layers may be used in conjunction with electrode plates 70 and 72. Driving arrangement of the ceramic body 16 through electrode plates 70 and 72 slightly increases the electrical resistance on the input side but use of electrode plates 70 and 72 not only increases the contact area for the ceramic body but also absorbs the vibration energy transmitted to the input lead wires 22 and 24 by the resiliency of the electrode plates thus preventing breakage fault of the lead wires.

FIG. 8 illustrates still another modification of this invention wherein electrode plates 70 and 72 applied on the opposite sides of the driving portion 12 of the ceramic body 16 are supported by a pair of stationary stays 80 and 82 through a pair of supporting rods 84 and 86 of resilient electroconductive rubber. Input lead wires 22 and 24 are electrically connected to electrode plates 70 and 72, respectively by wrapping one end of each of the lead wires around supporting rods 84 and 86 near stays 80 and 82. With this construction, vibrations due to the operation of the piezoelectric transformer are absorbed by the resiliency of the supporting rods 84 and 86 and thus preventing them from being transmitted to input lead wires connected to the outer ends of the supporting rods. In this manner input lead wires are well protected against breakage.

Although the invention has been shown and described in terms of some preferred embodiments thereof it should be understood that the invention is not limited to these embodiments and that many modifications may be made within the true spirit and scope of the invention as defined in the appended claims. As used in the claims the term rubber will be understood to include any elastomer having the electric and mechanical properties specified.

What is claimed is:

-1. A piezoelectric transformer comprising a rectangular plate-shaped ceramic body with one-half of its length polarized in the direction of thickness and the remaining half polarized in the axial direction, a pair of 4 input electrodes applied on the opposite surfaces of said one-half polarized in the direction of thickness, and an output electrode on the outer end of said remaining half polarized in the axial direction, the improvement which comprises an output electrode of conductive rubber, said output electrode being fitted over the outer end of said longitudinally polarized half of said ceramic body and having an integral stem extension adapted for connection to a lead wire remote from said output electrode.

2. A piezoelectric transformer comprising a rectangular plate shaped ceramic body with one half of its length polarized in the direction of thickness and the remaining half polarized in the longitudinal direction, a pair of input electrode plates of conductive rubber, said electrode plates covering and in direct electric contact with substantially the entire surface of said half polarized in thedirection of thickness, means to fixedly secure said electrode plates'to said ceramic body and adapted to support said ceramic body, and an output electrode of conductive rubber fitted over the outer end of said remaining half polarized in the longitudinal direction.

3. The piezoelectric transformer according to claim 2 wherein said input electrode plates include integral means to connect said input lead wires to said electrode plates.

4. The piezoelectric transformer according to claim 3 wherein said integral means comprise axial extensions of said electrode plates.

5. The piezoelectric transformer according to claim 3 wherein said integral means comprise projections vertically extending from the surface of said electrode plates.

6. The piezoelectric transformer according to claim 2 wherein said clamping means comprises a pair of stationary stays spaced apart from said ceramic bodies and a pair of supporting rods arranged betweenrespective stays and said electrode plates, said supporting rods being made of elastic conductive rubber and wherein said input leads wires are connected to said supporting rods at portions thereof close to said stays.

Claims (6)

1. A piezoelectric transformer comprising a rectangular plate shaped ceramic body with one-half of its length polarized in the direction of thickness and the remaining half polarized in the axial direction, a pair of input electrodes applied on the opposite surfaces of said one-half polarized in the direction of thickness, and an output electrode on the outer end of said remaining half polarized in the axial direction, the improvement which comprises an output electrode of conductive rubber, said output electrode being fitted over the outer end of said longitudinally polarized half of said ceramic body and having an integral stem extension adapted for connection to a lead wire remote from said output electrode.

2. A piezoelectric transformer comprising a rectangular plate shaped ceramic body with one half of its length polarized in the direction of thickness and the remaining half polarized in the longitudinal direction, a pair of input electrode plates of conductive rubber, said electrode plates covering and in direct electric contact with substantially the entire surface of said half polarized in the direction of thickness, means to fixedly secure said electrode plates tO said ceramic body and adapted to support said ceramic body, and an output electrode of conductive rubber fitted over the outer end of said remaining half polarized in the longitudinal direction.

3. The piezoelectric transformer according to claim 2 wherein said input electrode plates include integral means to connect said input lead wires to said electrode plates.

4. The piezoelectric transformer according to claim 3 wherein said integral means comprise axial extensions of said electrode plates.

5. The piezoelectric transformer according to claim 3 wherein said integral means comprise projections vertically extending from the surface of said electrode plates.

6. The piezoelectric transformer according to claim 2 wherein said clamping means comprises a pair of stationary stays spaced apart from said ceramic bodies and a pair of supporting rods arranged between respective stays and said electrode plates, said supporting rods being made of elastic conductive rubber and wherein said input leads wires are connected to said supporting rods at portions thereof close to said stays.

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