Piezoelectric transformer

There is provided a piezoelectric transformer including (a) a cylindrical body made of piezoelectric material and longitudinally defining a driven section and a voltage generating section, the voltage generating section being polarized in one of directions in a direction of a longitudinal axis of the cylindrical body, (b) a pair of first electrodes formed at a curved surface of the cylindrical body in the driven section and defining a plurality of regions in the driven section in a direction of a longitudinal axis of the cylindrical body, the first electrodes being electrically isolated with each other, the regions being polarized so that every other regions are polarized in opposite directions in a direction of a longitudinal axis of the cylindrical body, the pair of first electrodes comprising a plurality of strip-shaped electrodes wound around the cylindrical body and disposed in parallel with one another in a direction of a longitudinal axis of the cylindrical body, every other strip-shaped electrodes being in electrical communication with one another so that they have a common voltage, and (c) a second electrode cooperating with one of the first electrodes located closer to the voltage generating section to make a pair therewith. In accordance with the above mentioned piezoelectric transformer, it is possible to prevent edges of a piezoelectric body from being chipped, because of its cylindrical shape. Thus, it is also possible to prevent destruction of a transformer originated from chipping thereof, resulting in higher reliability of a piezoelectric transformer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a piezoelectric transformer, and more particularly 
to a piezoelectric transformer formed at a surface thereof with input and 
output electrodes. The invention relates also to a support for a 
piezoelectric transformer. 
2. Description of the Prior Art 
There has been widely used a coil-wound type electromagnetic transformer as 
a transforming device for generating a higher voltage to be used for 
equipments which requires a high voltage, such as a deflector for a 
cathode ray tube and a charging device for a copier. 
On the other hand, a piezoelectric transformer utilizing piezoelectric 
effect becomes popular for generating a high voltage. FIG. 1A illustrates 
one of conventional piezoelectric transformers. The illustrated 
piezoelectric transformer includes a rectangular planar piezoelectric body 
131 defining a driven section 135 and a voltage generating section 136 in 
a direction of a longitudinal axis of the piezoelectric body 131. The 
piezoelectric body 131 is formed on an upper surface in the driven section 
135 with a first electrode 132, and on a lower surface with a second 
electrode 133 in alignment with the first electrode 132. The first and 
second electrodes 121 and 133 are electrically insulated with each other, 
and it is possible to apply a voltage thereacross. 
The piezoelectric body 131 is formed at an end surface in the voltage 
generating section 136 with a third electrode 137. The piezoelectric body 
131 including the three electrodes 132, 133 and 137 is polarized in a 
widthwise direction thereof in the driven section as indicated with an 
arrow X1, and polarized in a lengthwise direction thereof in the voltage 
generating section 136 as indicated with an arrow X2. The piezoelectric 
transformer is supported and fixed on a support 139 at the center in a 
direction of a longitudinal axis thereof. 
In order to boost a voltage by means of the illustrated piezoelectric 
transformer, an ac voltage Ein is first applied across the first and 
second electrodes 132 and 133. The ac voltage Ein is selected to have a 
frequency equal to a resonance frequency of a longitudinal oscillation of 
the piezoelectric body 131. By applying the thus selected ac voltage 
across the first and second electrodes 132 and 133, the piezoelectric body 
131 is mechanically resonated, resulting in that a voltage Eout which is 
higher than Ein and has the same frequency as that of Ein is generated at 
the voltage generating section 136. The thus generated higher voltage Eout 
can be obtained between the second (or first) electrode 133 and the third 
electrode 137. The support 139 supports the piezoelectric transformer at a 
nodal point of longitudinal oscillation of the piezoelectric body 131. 
The above mentioned operation concerns only voltage step-up. By 
substituting the first and second electrodes 132 and 133 used as input 
ports and the third electrode 137 used as an output port with each other, 
that is, by applying an ac voltage across the second and third electrodes 
133 and 137 and obtaining a voltage between the first and second 
electrodes 132 and 133, the illustrated piezoelectric transformer acts 
also as a step-down transformer. It depends on the purpose of using the 
piezoelectric transformer whether electrodes formed on a surface of a 
piezoelectric body are used as input or output electrodes, and whether 
sections defined in a piezoelectric body are used as driven or voltage 
generating sections. 
In order to put the above mentioned piezoelectric transformer illustrated 
in FIG. 1A to practical use, it is necessary to provide the first to third 
electrodes 132, 133 and 137 with a terminal such as a lead wire for 
electrically connecting the piezoelectric transformer to an external 
circuit. However, such lead wires are not always connected to the 
electrodes 132, 133 and 137 both in the driven and voltage generating 
sections 135 and 136 at nodal points of mechanical oscillation of the 
piezoelectric body 131. Thus, the lead wires connected to the electrodes 
are often broken down. In order to enhance reliability in connection 
between the surface electrodes and the lead wires, it is effective that 
lead wires are connected to surface electrodes at nodal points of 
oscillation of a piezoelectric body. To this end, there are often defined 
three sections in a piezoelectric body. 
FIG. 1B illustrated an example of a piezoelectric transformer having a 
piezoelectric body 141 including three sections defined therein in a 
direction of a longitudinal axis thereof. Namely, the piezoelectric body 
141 includes a left side driven section 145L, a right side driven section 
145R, and a voltage generating section sandwiched the driven sections 145L 
and 145R. The voltage generating section is partitioned into two sections 
146L and 146R by a strip-shaped electrode 147 wound around the 
piezoelectric body 141 at a longitudinal midpoint of the piezoelectric 
body 141. Thus, the piezoelectric body 141 includes four sections: the 
left side driven section 145L, left side voltage generating section 146L, 
right side voltage generating section 146R and right side driven section 
145R, which sections are arranged symmetrically about the electrode 147. 
The piezoelectric body 141 is formed on upper and lower surfaces thereof 
in the left side driven section 145L with input electrodes 142L and 143L. 
Similarly, the piezoelectric body 141 is formed on upper and lower 
surfaces thereof in the right side driven section 145R with input 
electrodes 142R and 143R. The driven sections 143L and 143R are polarized 
in a thicknesswise direction of the piezoelectric body 141, as indicated 
with an upwardly directed arrow X1. The voltage generating sections 146L 
and 146R are polarized in a lengthwise direction of the piezoelectric body 
141, similarly to the piezoelectric transformer illustrated in FIG. 1A, 
but in opposite directions, as indicated with arrows X2 and X3. That is, 
the left side voltage generating section 146L is polarized to the left in 
a direction of a longitudinal axis of the piezoelectric body 141, as 
indicated with the arrow X2, whereas the right side voltage generating 
section 146R is polarized to the right in a direction of a longitudinal 
axis of the piezoelectric body 141, as indicated with the arrow X3. The 
upper input electrodes 142L and 142R are electrically connected by a wire 
W1, and the lower input electrodes 143L and 143R are electrically 
connected by a wire W2. An ac voltage Ein is applied across the upper 
input electrodes 142L and 142R and the lower input electrodes 143L and 
143R through the wires W1 and W2. An output voltage Eout, which is higher 
than Ein, is obtained between the electrode 147 and the upper input 
electrodes 142L and 142R. The ac voltage Ein is selected to have a 
frequency which causes tertiary resonance in a direction of a longitudinal 
axis of the piezoelectric body 141. By applying the thus selected ac 
voltage Ein to the electrodes, the piezoelectric body 141 has three nodal 
points in oscillation thereof: a point A1 at a distance of one-sixth of a 
full longitudinal length L of the piezoelectric body 141 away from an end 
surface 14a of the piezoelectric body 141; a point A2 at a distance of 
one-sixth of the length L away from the other end surface 141b of the 
piezoelectric body 141; a point A3 located at the midpoint of the length 
L. Thus, it is possible to prevent break-down of lead wires due to 
oscillation of the piezoelectric body 141 by connecting the lead wires to 
the surface electrodes 142L, 143L, 142R, 143R and 147 at the nodal points 
A1, A2 and A3. 
The planar piezoelectric transformers as mentioned above is small in size, 
but can produce a high voltage, and hence is very attractive, for 
instance, to an invertor to be used for a liquid crystal back light, which 
is requested to be smaller in size. However, the planar piezoelectric 
transformers still have the following problems to be solved which are 
accompanied by the fact that a piezoelectric transformer is planar. 
The first problem is as follows. When a piezoelectric body is oscillated, a 
larger internal stress is generated in the vicinity of nodal points of 
oscillation in the piezoelectric body. Specifically, tensile stresses are 
produced at a boundary between the driven section 135 and the voltage 
generating section 136 in the piezoelectric transformer illustrated in 
FIG. 1A and in the vicinity of the electrode 147 in the piezoelectric 
transformer illustrated in FIG. 1B, respectively, and thus the 
piezoelectric bodies 131 and 141 are in conditions to be readily 
destructive. A piezoelectric transformer is usually designed so that the 
tensile stress is lower than a critical value for destruction of a 
piezoelectric body. However, ceramic of which a piezoelectric body is 
often made is likely to be chipped even by small impact, and a chipping 
has occurred once in a piezoelectric body, the critical value is 
significantly lowered, resulting in that a piezoelectric body is easily 
destroyed. 
A chipping as mentioned above in a piezoelectric body is unavoidable in 
piezoelectric body fabrication steps and subsequent steps, and hence is a 
major factor for preventing enhancement in reliability to a piezoelectric 
transformer. In addition, a piezoelectric body has to be treated with the 
greatest possible care, which increases fabrication costs of a 
piezoelectric transformer. A chipping, reduction in reliability due to a 
chipping, and increased fabrication costs as mentioned above are problems 
in particular when a piezoelectric body is formed in a rectangular 
parallelopiped such as a plate and a prism. This is because a rectangular 
parallelopiped has many edges at which a chipping is prone to take place. 
The second problem of a planar piezoelectric transformer is that noises 
tend to be produced in audible ranges. Since a piezoelectric transformer 
utilizes mechanical oscillation, a frequency for operation of a 
piezoelectric transformer is selected to be in the range of about 30 to 
about 150 kHz which is beyond audible range. In a planar piezoelectric 
transformer, there would be generated longitudinal oscillation in a 
widthwise direction, bending oscillation and torsional oscillation as well 
as longitudinal oscillation in a direction of a longitudinal axis of a 
piezoelectric body. Thus, frequencies of those oscillations, a beat 
frequency between two different oscillations, and a beat frequency between 
higher mode frequency of various oscillations and another mode frequency 
enter audible range. Such frequencies entering audible range would be 
merely a noise to men's ears, which poses a problem in putting a planar 
piezoelectric transformer into practical use. Even if a piezoelectric 
transformer is fabricated in the form other than a plate, there would be 
produced various oscillation modes. However, a piezoelectric transformer 
fabricated in the form of a planar plate would quite readily produce 
unpreferable modes of oscillation, which oscillation in addition is likely 
to become greater in level. 
In order to solve the above mentioned problems caused by the fact that a 
piezoelectric body is planar in shape, there has been suggested 
piezoelectric bodies in various forms. 
U.S. Pat. No. 2,974,296 has suggested a columnar piezoelectric transformer. 
The piezoelectric transformer has a thin-walled columnar piezoelectric 
body defining three sections in a direction of a longitudinal axis 
thereof. Ring-shaped electrodes are wound around the piezoelectric body at 
boundaries among the three sections and at opposite ends. Among the four 
electrodes disposed longitudinally of the piezoelectric body, two of the 
internally located electrodes are used as driven electrodes, whereas two 
of the externally located electrodes are used as voltage generating 
electrodes. Since it is difficult in the above mentioned piezoelectric 
transformer to make a step-up ratio greater, which is defined as a ratio 
of an input voltage to an output voltage, U.S. Pat. No. 2,974,296 has also 
suggested a piezoelectric transformer including a driven section defined 
between outer and inner surfaces of a piezoelectric body, and a voltage 
generating section defined over a full length of a piezoelectric body. 
Japanese Unexamined Patent Publication No. 2-311181 has suggested a 
columnar piezoelectric motor including cross type finger electrodes. 
Japanese Unexamined Patent Publication No. 2-163982 has suggested a 
piezoelectric actuator including electrodes spirally extending on an outer 
surface thereof. 
Japanese Unexamined Patent Publication No. 4-307322 has suggested a 
columnar piezoelectric gyro. 
The piezoelectric transformer suggested in U.S. Pat. No. 2,974,296 does not 
have purposes of prevention of chipping in a piezoelectric body and 
prevention of noises. The above mentioned piezoelectric motor, 
piezoelectric actuator and piezoelectric gyro are devices used for 
electrical-mechanical energy conversion or mechanical-electrical energy 
conversion. In a device such as a motor or a gyro necessarily including 
mechanical rotation, a piezoelectric body is inevitably columnar in shape. 
In contrast, a piezoelectric transformer acting as an 
electrical-mechanical energy convertor may have any shape, but it is not 
known so far to fabricate a piezoelectric transformer including a 
cylindrical piezoelectric body. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a piezoelectric 
transformer free of chipping at edges of a piezoelectric body in 
fabrication thereof. By preventing chipping at edges of a piezoelectric 
body, it is possible to prevent a piezoelectric transformer from being 
destroyed due to chipping thereof with the result of higher reliability, 
and also possible to treat a piezoelectric transformer without so great 
care to thereby enhance fabrication efficiency and non-defectiveness rate, 
resulting in lower fabrication costs. 
Another object of the present invention is to suppress unnecessary mode of 
oscillations. This ensures that noises are prevented from being produced 
in audible frequency range when a piezoelectric transformer is in 
operation, and that it is no longer necessary to take removal of 
unnecessary modes of oscillation into consideration in designing a 
piezoelectric transformer, resulting in that a piezoelectric body can be 
more readily designed. 
A further object of the present invention is to provide a piezoelectric 
transformer small in size and having a great step-up ratio without 
sacrificing a shape of a piezoelectric transformer. 
A still further object of the present invention is to provide a support for 
supporting a piezoelectric transformer which accomplishes the above 
mentioned objects. 
There is provided a piezoelectric transformer including (a) a piezoelectric 
body made of piezoelectric material and longitudinally defining a driven 
section and a voltage generating section, the piezoelectric body being 
cylindrical in shape, (b) a pair of input electrodes formed at a curved 
surface of the piezoelectric body in the driven section for receiving ac 
voltage to oscillate the piezoelectric body to cause the piezoelectric 
body to produce a voltage, and (c) an output electrode cooperating with 
one of the input electrodes to introduce the voltage therethrough. 
There is further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining a driven section and a voltage generating section, the voltage 
generating section being polarized in one of directions in a direction of 
a longitudinal axis of the cylindrical body, (b) a pair of first 
electrodes formed at a curved surface of the cylindrical body in the 
driven section and defining a plurality of regions in the driven section 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes being electrically isolated with each other, the regions being 
polarized so that every other regions are polarized in opposite directions 
in a direction of a longitudinal axis of the cylindrical body, and (c) a 
second electrode cooperating with one of the first electrodes located 
closer to the voltage generating section to make a pair therewith. 
There is still further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining a driven section and a voltage generating section, the voltage 
generating section being polarized in one of directions in a direction of 
a longitudinal axis of the cylindrical body, (b) a pair of first 
electrodes formed at a curved surface of the cylindrical body in the 
driven section and defining a plurality of regions in the driven section 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes being electrically isolated with each other, the regions being 
polarized so that every other regions are polarized in opposite directions 
in a direction of a longitudinal axis of the cylindrical body, the pair of 
first electrodes comprising a plurality of strip-shaped electrodes wound 
around the cylindrical body and disposed in parallel with one another in a 
direction of a longitudinal axis of the cylindrical body, every other 
strip-shaped electrodes being in electrical communication with one another 
so that they have a common voltage, and (c) a second electrode cooperating 
with one of the first electrodes located closer to the voltage generating 
section to make a pair therewith. 
The strip-shaped electrodes may have the same width, and may be equally 
spaced with one another in a direction of a longitudinal axis of the 
cylindrical body. 
It is preferable for the first electrodes to receive ac voltage having a 
frequency which causes longitudinal oscillation generated in the 
cylindrical body to make first or higher order resonance in the 
cylindrical body. The cylindrical body may have any diameter and/or 
height, but it is preferable that it has a diameter equal to a height 
thereof. 
The first and second electrodes may be formed by curved-surface printing 
silver paste around the cylindrical body, and baking the silver paste. 
The driven section may include one of end surfaces of the cylindrical body 
and the voltage generating section may include the other, and the second 
electrode may be formed at the other end surface of the cylindrical body. 
As an alternative, the second electrode may be formed at a curved surface 
and adjacent to the other end surface of the cylindrical body in place of 
being formed at the other end surface of the cylindrical body. 
There is yet further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining a driven section and a voltage generating section, the voltage 
generating section being polarized in one of directions in a direction of 
a longitudinal axis of the cylindrical body, (b) a pair of first 
electrodes formed at a curved surface of the cylindrical body in the 
driven section and defining a plurality of regions in the driven section 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes being electrically isolated with each other, the regions being 
polarized so that every other regions are polarized in opposite directions 
in a direction of a longitudinal axis of the cylindrical body, each of the 
pair of first electrodes including a plurality of finger electrodes wound 
circumferentially around the cylindrical body and disposed in parallel 
with one another in a direction of a longitudinal axis of the cylindrical 
body, the finger electrodes having ends spaced away from each other, and a 
connection electrode extending between the ends of finger electrodes of 
the associated first electrode in a direction of a longitudinal axis of 
the cylindrical body and connecting the finger electrodes thereto, the 
finger electrodes of the pair of first electrodes being alternately 
arranged in parallel with each other, and (c) a second electrode 
cooperating with one of the first electrodes located closer to the voltage 
generating section to make a pair therewith. 
There is further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining a driven section and a voltage generating section, the voltage 
generating section being polarized in one of directions in a direction of 
a longitudinal axis of the cylindrical body, (b) a pair of first 
electrodes formed at a curved surface of the cylindrical body in the 
driven section and defining a plurality of regions in the driven section 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes being electrically isolated with each other, the regions being 
polarized so that every other regions are polarized in opposite directions 
in a direction of a longitudinal axis of the cylindrical body, each of the 
pair of first electrodes comprising a spiral electrode, and (c) a second 
electrode cooperating with one of the first electrodes located closer to 
the voltage generating section to make a pair therewith. 
There is further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining two driven sections and a voltage generating section sandwiched 
between the driven sections, each of the driven sections including an end 
surface of the cylindrical body, the voltage generating section being 
polarized in one of directions in a direction of a longitudinal axis of 
the cylindrical body, (b) two pairs of first electrodes each of which is 
formed at a curved surface of the cylindrical body in each of the driven 
sections and defines a plurality of regions in each of the driven sections 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes in each of the pairs being electrically isolated with each 
other, the regions in each of the driven sections being polarized so that 
every other regions are polarized in opposite directions in a direction of 
a longitudinal axis of the cylindrical body, and (c) a second electrode 
formed in the voltage generating section, the second electrode cooperating 
with first electrodes located closer to the voltage generating section to 
make a pair therewith. 
It is preferable that the regions in the driven sections are polarized 
symmetrically about the second electrode. The piezoelectric transformer 
may further include a plurality of lead wires for electrically connecting 
the piezoelectric transformer to an external terminal, the lead wires 
being connected to the piezoelectric transformer at nodes established in 
the cylindrical body when ac voltage is applied to the driven sections to 
thereby longitudinally oscillate the cylindrical body. 
There is further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining two driven sections and a voltage generating section sandwiched 
between the driven sections, each of the driven sections including an end 
surface of the cylindrical body, the voltage generating section being 
polarized in one of directions in a direction of a longitudinal axis of 
the cylindrical body, (b) two pairs of first electrodes each of which is 
formed at a curved surface of the cylindrical body in each of the driven 
sections and defines a plurality of regions in each of the driven sections 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes in each of the pairs being electrically isolated with each 
other, the regions in each of the driven sections being polarized so that 
every other regions are polarized in opposite directions in a direction of 
a longitudinal axis of the cylindrical body, each of the pairs of first 
electrodes comprising a plurality of strip-shaped electrodes wound around 
the cylindrical body and disposed in parallel with one another in a 
direction a longitudinal axis of the cylindrical body, every other 
strip-shaped electrodes being in electrical communication with one another 
so that they have a common voltage, and (c) a second electrode comprising 
a strip-shaped electrode wound around the cylindrical body at the 
longitudinal midpoint thereof, the second electrode cooperating with first 
electrodes located closer to the voltage generating section to make a pair 
therewith. 
There is further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining two driven sections and a voltage generating section sandwiched 
between the driven sections, each of the driven sections including an end 
surface of the cylindrical body, the voltage generating section being 
polarized in one of directions in a direction of a longitudinal axis of 
the cylindrical body, (b) two pairs of first electrodes each of which is 
formed at a curved surface of the cylindrical body in each of the driven 
sections and defines a plurality of regions in each of the driven sections 
in a direction of a longitudinal axis of the cylindrical body, the first 
electrodes in each of the pairs being electrically isolated with each 
other, the regions in each of the driven sections being polarized so that 
every other regions are polarized in opposite directions in a direction of 
a longitudinal axis of the cylindrical body, each of the pairs of first 
electrodes comprising a plurality of finger electrodes wound 
circumferentially around the cylindrical body and disposed in parallel 
with one another in a direction of a longitudinal axis of the cylindrical 
body, the finger electrodes having ends spaced away from each other, and a 
connection electrode extending between the ends of finger electrodes of 
the associated first electrode in a direction of a longitudinal axis of 
the cylindrical body and connecting the finger electrodes thereto, the 
finger electrodes of the pair of first electrodes being alternately 
arranged in parallel with each other, and (c) a second electrode 
comprising a strip-shaped electrode wound around the cylindrical body at 
the longitudinal midpoint thereof, the second electrode cooperating with 
first electrodes located closer to the voltage generating section to make 
a pair therewith. 
There is further provided a piezoelectric transformer including (a) a 
cylindrical body made of piezoelectric material and longitudinally 
defining two driven sections and a voltage generating section sandwiched 
between the driven sections, each of the driven sections including an end 
surface of the cylindrical body, (b) two pairs of first electrodes each of 
which is formed at a curved surface of the cylindrical body in each of the 
driven sections and defines a plurality of regions in each of the driven 
sections in a direction of a longitudinal axis of the cylindrical body, 
the first electrodes in each of the pairs being electrically isolated with 
each other, the regions in each of the driven sections being polarized so 
that every other regions are polarized in opposite directions in a 
direction of a longitudinal axis of the cylindrical body, each of the 
first electrodes comprising a spiral electrode, and (c) a second electrode 
comprising a strip-shaped electrode wound around the cylindrical body at 
the longitudinal midpoint thereof, the second electrode cooperating with 
first electrodes located closer to the voltage generating section to make 
a pair therewith. 
There is further provided a support for supporting a piezoelectric 
transformer therewith. Herein, the piezoelectric transformer includes (a) 
a cylindrical body made of piezoelectric material longitudinally defining 
a driven section and a voltage generating section, (b) a pair of input 
electrodes formed at a curved surface of the cylindrical body in the 
driven section for receiving ac voltage to oscillate the cylindrical body 
to cause the cylindrical body to produce a voltage, and (c) an output 
electrode cooperating with one of the input electrodes to introduce the 
voltage therethrough. The support is made of resilient, electrically 
insulating material and supports the piezoelectric transformer at nodes 
established in the cylindrical body when ac voltage is applied to the 
driven section to thereby longitudinally oscillate the cylindrical body. 
There is further provided a support for supporting a piezoelectric 
transformer therewith, including (a) an enclosure through which the 
cylindrical body can be inserted, and (b) resilient, electrically 
insulating material to be sandwiched between an inner surface of the 
enclosure and an outer surface of the cylindrical body. 
The support may further include a housing in which the enclosure is fixed 
to the housing. The enclosure may be ring-shaped. The insulating material 
is preferably silicone resin. The support supports the piezoelectric 
transformer preferably at a longitudinal midpoint of the cylindrical body. 
There is further provided a support for supporting a piezoelectric 
transformer therewith, including a plurality of supporting members made of 
resilient, electrically conductive material and supporting the 
piezoelectric transformer at the first and second electrodes therewith, 
the first and second electrodes being in electrical communication with an 
external terminal through the supporting members. 
There is provided a support for supporting a piezoelectric transformer 
therewith, including (a) an enclosure made of electrically insulating 
material for enclosing the piezoelectric transformer therein, the 
enclosure being formed at an outer wall thereof with a plurality holes, 
and (b) resilient, electrically conductive material filled in the holes 
and making contact with the first electrodes, which are in electrical 
connection with an external terminal through the electrically conductive 
material. 
There may be formed first and second sets of holes, each of the first and 
second sets of holes being formed in alignment with each of the first 
electrodes. The enclosure may have any shape. For instance, the enclosure 
may be rectangular or circular in shape. When the enclosure is formed to 
be rectangular in shape, the first and second sets of holes may be formed 
with each of planes of the enclosure facing each other, in which case, the 
resilient, electrically conductive material filled in the first and second 
sets of holes is in electrical connection with each other, respectively. 
It is preferable that the planes make tangential contact with the 
cylindrical body. 
In accordance with the present invention, a piezoelectric transformer has a 
cylindrical piezoelectric body. By applying an ac voltage to a driven 
section, there is produced an electric field having alternate polarities 
in a direction of a longitudinal axis of the cylindrical piezoelectric 
body. The regions polarized so that every other regions are polarized in 
opposite directions in a direction of a longitudinal axis of said 
cylindrical body are synchronized with the thus produced electric field, 
and thus there is produced a single longitudinal oscillation along a 
longitudinal axis of the cylindrical piezoelectric body. An ac voltage 
applied to the input electrodes is selected to have a frequency which 
causes the longitudinal oscillation generated in the piezoelectric body to 
make first or higher order resonance in the piezoelectric body. The thus 
induced oscillation in the piezoelectric body produces an ac voltage in 
the voltage generating section. The thus produced ac voltage is higher 
than and has the same frequency as the ac voltage applied to the driven 
section The thus produced step-up ac voltage is obtained through the 
electrode formed at the voltage generating section. 
The cylindrical piezoelectric body in the present invention has edges only 
in opposite bottom surfaces thereof. Since the cylindrical piezoelectric 
body had the smaller number of edges than a planar piezoelectric body, the 
possibility of occurrence of chipping is smaller. In addition, edges of 
bottom surfaces of the cylindrical piezoelectric body are not parts where 
a tensile stress is generated. Hence, even if an edge of the cylindrical 
piezoelectric body is chipped, there is quite small possibility of 
complete destruction of a piezoelectric transformer. Thus, higher 
reliability is ensured than a conventional piezoelectric transformer. In 
addition, a piezoelectric transformer in accordance with the present 
invention can be more readily treated in fabrication process, resulting in 
enhancement in fabrication efficiency and non-defectiveness rate, which 
reduces the fabrication costs of a piezoelectric transformer. 
Oscillation modes readily produced in a cylindrical piezoelectric body is 
simpler than those produced in a planar piezoelectric body. The primary 
oscillation mode is a longitudinal oscillation in a direction of a 
longitudinal axis of a cylindrical piezoelectric body, and the secondary 
mode is bending oscillation. Torsional oscillation needs much energy to be 
produced, and hence there is scarcely produced a great level of torsional 
oscillation. The bending oscillation can be produced more readily than 
torsional oscillation, but needs much more energy to be produced than a 
bending of a planar plate having the same cross-sectional area. Hence, 
even if the bending oscillation would be produced as unnecessary 
oscillation mode, the oscillation level is smaller than that of a planar 
piezoelectric body. Thus, a cylindrical piezoelectric body in accordance 
with the present invention has quite smaller possibility than a planar 
piezoelectric body in terms of production of noises exerting harmful 
influence on audible frequency. 
As well known in those skilled in the art, the electric power a 
piezoelectric transformer can deal with is in proportion to a 
cross-sectional area through which oscillation of a piezoelectric 
transformer is propagated, as first order approximation. The cylindrical 
piezoelectric body used in a piezoelectric transformer in accordance with 
the present invention has a greater cross-sectional area than that of a 
piezoelectric body used in a piezoelectric transformer disclosed in the 
above mentioned U.S. Pat. No. 2,974,296. Accordingly, the present 
invention provides a piezoelectric transformer smaller in size, but having 
a greater step-up ratio. In particular, if the cylindrical piezoelectric 
body is designed to have a diameter equal to a height thereof, such a 
geometry is quite advantageous for certain applications in comparison with 
a planar piezoelectric body. 
A support in accordance with the present invention ensures that a 
piezoelectric transformer can be readily supported by a simply structured 
support without reduction in transformation efficiency of a piezoelectric 
transformer. 
The above and other objects and advantageous features of the present 
invention will be made apparent from the following description made with 
reference to the accompanying drawings, in which like reference characters 
designate the same or similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First Embodiment! 
With reference to FIG. 2, a piezoelectric body 1 is formed by shaping 
piezoelectric ceramic material available from Kabushiki Kaisha Tokin, 
Japan, under the tradename of Nepec 8, baking the material, and finishing 
it to a cylinder having a diameter of 2.5 mm and a length of 42 mm. The 
cylindrical piezoelectric body 1 includes two sections: a driven section 
12 and a voltage generating section 13 defined in a direction of a 
longitudinal axis of the piezoelectric body 1. The piezoelectric body 1 
includes the n number of strip-shaped electrodes 14-1 to 14-n wound 
therearound in the driven section 12. The strip-shaped electrodes 14-1 to 
14-n have the same width and are equally spaced away from one another in a 
direction of a longitudinal axis of the cylindrical piezoelectric body 1. 
The cylindrical piezoelectric body 1 is formed at an end or bottom surface 
1a with an electrode 4 in the voltage generating section 13. The 
electrodes 14-1 to 14-n and 4 are formed by printing silver paste on a 
curved surface and the end surface 1a of the cylindrical piezoelectric 
body 1, and baking the silver paste. Each of the electrodes 14-1 to 14-n 
and 4 has a thickness of about 15 .mu.m. 
After the formation of the electrodes 14-1 to 14-n and 4, the i-th 
electrodes are connected with one another through a lead wire W1 wherein i 
is an odd number, and the k-th electrodes are connected with one another 
through a lead wire W2 wherein k is an even number so that every other 
electrodes are in the same voltage. That is, the electrodes 14-1, 14-3, 
14-5,--are electrically connected with one another and further to a 
terminal 2A through the lead wire W1, and the electrodes 14-2, 14-4, 
14-6,--are electrically connected with one another and further to a 
terminal 2B through the lead wire W2 in order to polarize the driven 
section 12. Polarization is accomplished by applying a dc field in the 
range of 2 to 3 kV per 1 mm of a space between the adjacent strip-shaped 
electrodes to the strip-shaped electrodes in silicone oil heated in the 
range of 100.degree. C. to 200.degree. C. By accomplishing the 
polarization, regions between the adjacent strip-shaped electrodes are 
polarized so that every other regions is polarized in opposite directions 
in a direction of a longitudinal axis of the cylindrical piezoelectric 
body 1, as indicated with shorter arrows Y1. 
Then, the voltage generating section 13 is polarized. A dc field is applied 
across the electrode 4 formed on the end surface 1a and a strip-shaped 
electrode located closest to the voltage generating section 13, namely the 
strip-shaped electrode 14-1. The conditions for polarization are the same 
as those for polarization of the driven section 12. As a result, the 
voltage generating section 13 is polarized in a direction of a 
longitudinal axis of the cylindrical piezoelectric body 1, as indicated 
with a longer arrow Y2. 
The strip-shaped electrode located closest to the voltage generating 
section 13 or the strip-shaped electrode 14-1 is electrically connected to 
a terminal 3A, and the end surface electrode 4 is electrically connected 
to a terminal 3B. The terminals 3A and 3B cooperate with each other to 
define an output port, as mentioned later. 
In order to operate a piezoelectric transformer in accordance with the 
instant embodiment, an ac voltage Ein is applied across the terminal 2A 
connecting to the i-th number strip-shaped electrodes wherein i is an odd 
number and the terminal 2B connecting to the k-th number strip-shaped 
electrodes wherein k is an even number. The ac voltage Ein has a frequency 
of 38 kHz. By applying the ac voltage to the strip-shaped electrodes 14-1 
to 14-n, distortion is repeatedly produced through an electromechanical 
coupling factor k.sub.33 along a longitudinal axis of the cylindrical 
piezoelectric body 1. As a result, resonant longitudinal oscillation is 
generated in the piezoelectric body 1 in a direction of a longitudinal 
axis of the cylindrical piezoelectric body 1 with the end surface 1a being 
as an open end. The thus generated resonant longitudinal oscillation 
produces a voltage in the voltage generating section 13 through the 
electromechanical coupling factor k.sub.33 between the end surface 
electrode 4 and the strip-shaped electrode 14-1. The thus produced voltage 
Eout is obtained through the terminals 3A and 3B. 
In the instant embodiment, each of the strip-shaped electrodes 14-1 to 14-n 
had a width of 0.2 mm, and the adjacent strip-shaped electrodes were 
spaced away from each other by 0.8 mm. The piezoelectric transformer in 
accordance with the instant embodiment could deal with electric power of 
about 2 W. The step-up ratio which is defined as Eout/Ein was about 30. 
In the instant embodiment, the maximum tensile stress is generated in the 
vicinity of the strip-shaped electrode 14-1. There was conducted a test 
for a sufficient number of piezoelectric transformers in accordance with 
the above mentioned embodiment. In the test, after the piezoelectric 
transformers were treated in fabrication process with care which would be 
usually taken for treating ceramics, they were experimentally operated 
with electric power of about 5 W. The result was that destruction never 
occurred in all of the tested piezoelectric transformers. 
The audible noises were below 25 dB at a distance of 5 cm away from the 
tested piezoelectric transformer, which poses no problem in practical use. 
Second Embodiment! 
FIG. 3 illustrates a piezoelectric transformer in accordance with the 
second embodiment. The second embodiment is different from the first 
embodiment in shape of electrodes in a driven section and how a driven 
section is polarized. 
Similarly to the first embodiment, the cylindrical piezoelectric body 1 
includes two sections: a driven section 22 and a voltage generating 
section 23 defined in a direction of a longitudinal axis of the 
piezoelectric body 1. There are formed a pair of first electrodes 24a and 
24b on a curved surface of the cylindrical piezoelectric body in the 
driven section 22. Each of the first electrodes 24a and 24b includes a 
plurality of finger electrodes 25 wound circumferentially around the 
piezoelectric body 1 and disposed in parallel with one another in a 
direction of a longitudinal axis of the piezoelectric body 1. Each of the 
finger electrodes 25 has ends 25a spaced away from each other by a certain 
distance. The finger electrodes 25 have the same width and are equally 
spaced away from each other. Each of the first electrodes 24a and 24b 
further includes a connection electrode 26 extending between the ends 25a 
of the finger electrodes 25 of the associated first electrode in a 
direction of a longitudinal axis of the piezoelectric body 1 and 
connecting the finger electrodes 25 thereto. The finger electrodes 25 of 
each of the first electrodes 24a and 24b are alternately arranged in 
parallel with each other. 
Similarly to the first embodiment, the cylindrical piezoelectric body 1 is 
formed at an end or bottom surface 1a with an electrode 4 in the voltage 
generating section 23. The electrodes 24a, 24b and 4 are formed by 
printing silver paste on a curved surface and the end surface 1a of the 
cylindrical piezoelectric body 1, and baking the silver paste. Each of the 
electrodes 24a, 24b and 4 has a thickness of about 15 .mu.m. 
After the formation of the electrodes 24a, 24b and 4, the driven section 22 
is polarized. Polarization is accomplished by applying a dc field in the 
range of 2 to 3 kV per 1 mm of a space between the adjacent finger 
electrodes to the first electrodes 24a and 24b in silicone oil heated in 
the range of 100.degree. C. to 200.degree. C. By accomplishing the 
polarization, regions sandwiched the finger electrodes 25 are polarized so 
that every other regions is polarized in opposite directions in a 
direction of a longitudinal axis of the cylindrical piezoelectric body 1, 
as indicated with shorter arrows Y1. 
Then, the voltage generating section 23 is polarized. Before accomplishing 
polarization, the first electrodes 24a and 24b are electrically connected 
with each other through a wire to thereby have the same voltage. 
Thereafter, a dc field is applied across the electrode 4 formed on the end 
surface 1a and the first electrodes 24a, 24b kept in the same voltage. The 
conditions for polarization are the same as those for polarization of the 
driven section 22. As a result, the voltage generating section 23 is 
polarized in a direction of a longitudinal axis of the cylindrical 
piezoelectric body 1, as indicated with a longer arrow Y2. 
When the piezoelectric body 1 was designed to have the same dimensions as 
the piezoelectric body 1 in the first embodiment, each of the finger 
electrodes 25 was designed to have a width of 0.2 mm, and the adjacent 
finger electrodes 25 were designed to be spaced away from each other by 
0.8 mm, the piezoelectric transformer in accordance with the instant 
embodiment could deal with electric power of about 2 W. The step-up ratio 
was about 25. There never happened chipping or destruction of a 
piezoelectric transformer, and there were never produced audible noises 
which would pose a problem in practical use. 
In the second embodiment, the finger electrodes 25 are polarized not only 
in a direction of a longitudinal axis of the piezoelectric body 1, but 
also unpreferably in a circumferential direction at the ends 25a thereof. 
However, when the first electrodes 24a and 24b are formed, the finger 
electrodes 25 are electrically connected with one another in advance by 
printing so that they are in the same voltage, and hence it is no longer 
necessary to electrically connect them in another step unlike the first 
embodiment in which i-th and k-th strip-shaped electrodes are electrically 
connected with one another through wires W1 and W2, respectively, wherein 
i and k are odd and even numbers, respectively. Thus, the second 
embodiment ensures simpler fabrication process than that of the first 
embodiment. 
Third Embodiment! 
FIG. 4 illustrates a piezoelectric transformer in accordance with the third 
embodiment. The third embodiment is different from the first embodiment in 
shape of electrodes in a driven section and how a driven section is 
polarized. 
Similarly to the first embodiment, the cylindrical piezoelectric body 1 
includes two sections: a driven section 32 and a voltage generating 
section 33 defined in a direction of a longitudinal axis of the 
piezoelectric body 1. In the driven section 32, there are formed a pair of 
spiral electrodes 34a and 34b equally spaced away from each other. 
Specifically, the first spiral electrode 34a is a thin strip electrode, 
and starts at an end surface 1b of the piezoelectric body 1 and spirally 
extends around a curved surface of the piezoelectric body 1. The second 
spiral electrode 34b is also a thin strip electrode, and extends around a 
curved surface of the piezoelectric body 1 intermediate between the first 
spiral electrode 34a. 
Similarly to the first and second embodiments, the cylindrical 
piezoelectric body 1 is formed at an end or bottom surface 1a with an 
electrode 4 in the voltage generating section 33. The electrodes 34a, 34b 
and 4 are formed by printing silver paste on a curved surface and the end 
surface 1a of the cylindrical piezoelectric body 1, and baking the silver 
paste. Each of the electrodes 34a, 34b and 4 has a thickness of about 15 
.mu.m. 
After the formation of the electrodes 34a, 34b and 4, the driven section 32 
is polarized. Polarization is accomplished by applying a dc field in the 
range of 2 to 3 kV per 1 mm of a space between the adjacent spiral 
electrodes to the spiral electrodes 34a and 34b in silicone oil heated in 
the range of 100.degree. C. to 200.degree. C. By accomplishing the 
polarization, regions sandwiched the first and second spiral electrodes 
34a and 34b are polarized so that every other regions is polarized in 
opposite directions in a direction of a longitudinal axis of the 
cylindrical piezoelectric body 1, as indicated with shorter arrows Y1. 
Then, the voltage generating section 33 is polarized. Before accomplishing 
polarization, the first and second spiral electrodes 34a and 34b are 
electrically connected with each other through a wire to thereby have the 
same voltage. Thereafter, a dc field is applied across the electrode 4 
formed on the end surface 1a and both of the spiral electrodes 34a, 34b 
kept in the same voltage. The conditions for polarization are the same as 
those for polarization of the driven section 32. As a result, the voltage 
generating section 33 is polarized in a direction of a longitudinal axis 
of the cylindrical piezoelectric body 1, as indicated with a longer arrow 
Y2. 
In order to operate the piezoelectric transformer in accordance with the 
instant embodiment, an ac voltage having a frequency of about 38 kHz is 
applied across the spiral electrodes 34a and 34b. When the spiral 
electrodes 34a and 34b were designed to have a line width of 0.2 mm, and 
the adjacent spiral electrodes 34a and 34b were designed to be spaced away 
from each other by 0.8 mm, the piezoelectric transformer in accordance 
with the instant embodiment could deal with electric power of about 2 W. 
The step-up ratio was about 27. There never happened chipping or 
destruction of a piezoelectric transformer, and there were never produced 
audible noises which would pose a problem in practical use. 
Fourth Embodiment! 
FIG. 5 illustrates a piezoelectric transformer in accordance with the 
fourth embodiment of the present invention. The illustrated piezoelectric 
transformer has a cylindrical piezoelectric body 1. The piezoelectric body 
1 is formed by shaping piezoelectric ceramic material available from 
Kabushiki Kaisha Tokin, Japan, under the tradename of Nepec 8, baking the 
material, and finishing it into a cylinder having a diameter of 2.5 mm and 
a length of 42 mm. The cylindrical piezoelectric body 1 defines three 
sections in a direction of a longitudinal axis of the piezoelectric body 
1: a first driven section 42L including an end surface 1b of the 
cylindrical piezoelectric body 1; a second driven section 42R including 
the other end surface 1a of the cylindrical piezoelectric body 1; and a 
voltage generating section 43 sandwiched between the driven sections 42L 
and 42R. 
The piezoelectric body 1 includes the n number of strip-shaped electrodes 
44-1L to 44-nL wound therearound in the first driven section 42L. The 
strip-shaped electrodes 44-1L to 44-nL have the same width and are equally 
spaced away from one another in a direction of a longitudinal axis of the 
cylindrical piezoelectric body 1. In the same way, the piezoelectric body 
1 also includes the n number of strip-shaped electrodes 44-1R to 44-nR 
wound therearound in the second driven section 42R. 
An electrode 5 is wound around the cylindrical piezoelectric body 1 at the 
center of the voltage generating section 43. The electrodes 44-1L to 44nL, 
44-1R to 44-nR and 5 are formed by printing silver paste on a curved 
surface of the cylindrical piezoelectric body 1, and baking the silver 
paste. Each of the electrodes has a thickness of about 15 .mu.m. 
After the formation of the electrodes 44-1L to 44-nL, 44-1R to 44-nR and 5, 
the first and second driven sections 42L and 42R are polarized. For 
polarization, the strip-shaped electrodes are electrically connected with 
one another as follows. In the first driven section 42L, the i-th 
electrodes are connected with one another through a lead wire W1 wherein i 
is an odd number, and the k-th electrodes are connected with one another 
through a lead wire W2 wherein k is an even number so that every other 
electrodes are in the same voltage. Herein, strip-shaped electrodes 
located nearest the voltage generating section 43 are selected to be the 
first electrodes 44-1L and 44-1R. Similarly, in the second driven section 
42R, the i-th electrodes are connected with one another through a lead 
wire W3 wherein i is an odd number, and the k-th electrodes are connected 
with one another through a lead wire W4 wherein k is an even number so 
that every other electrodes are in the same voltage. That is, the 
electrodes 44-1L, 44-3L, 44-5L,--and 44-1R, 44-3R, 44-5R,--are 
electrically connected with one another and further to a terminal 2A 
through the lead wires W1 and W3, respectively, and the electrodes 44-2L, 
44-4L, 44-6L,--and 44-2R, 44-4R, 44-6R,--are electrically connected with 
one another and further to a terminal 2B through the lead wires W2 and W4, 
respectively. 
Polarization is accomplished by applying a dc field in the range of 2 to 3 
kV per 1 mm of a space between the adjacent strip-shaped electrodes to the 
strip-shaped electrodes in silicone oil heated in the range of 100.degree. 
C. to 200.degree. C. By accomplishing the polarization, regions between 
the adjacent strip-shaped electrodes are polarized so that every other 
regions is polarized in opposite directions in a direction of a 
longitudinal axis of the cylindrical piezoelectric body 1, as indicated 
with shorter arrows Y1. In addition, regions between the adjacent 
strip-shaped electrodes in the first driven section 42L are symmetrically 
polarized with regions between the adjacent strip-shaped electrodes in the 
second driven section 42R about the electrode 5 formed in the voltage 
generating section 43. 
Then, the voltage generating section 43 is polarized as follows. The lead 
wires W1 and W3 are electrically connected with each other so that the 
strip-shaped electrode 44-1L located closest to the voltage generating 
section 43 among the strip-shaped electrodes 44-1L to 44-nL in the first 
driven section 42L and the strip-shaped electrode 44-1R located closest to 
the voltage generating section 43 among the strip-shaped electrodes 44-1R 
to 44-nR in the second driven section 42R are in the same voltage. Then, a 
dc field is applied across the electrode 5 and the strip-shaped electrodes 
44-1L and 44-1R kept in the same voltage. The conditions for polarization 
are the same as those for polarization of the driven sections 42L and 42R. 
As a result, the voltage generating section 43 is polarized in opposite 
directions symmetrically about the electrode 5 in a direction of a 
longitudinal axis of the cylindrical piezoelectric body 1, as indicated 
with longer arrows Y2. 
The strip-shaped electrodes located closest to the voltage generating 
section 43 or the strip-shaped electrodes 44-1L and 44-1R are electrically 
connected to a terminal 3A, and the electrode 5 is electrically connected 
to a terminal 3B. The terminals 3A and 3B cooperate with each other to 
define an output port. 
In order to operate a piezoelectric transformer in accordance with the 
instant embodiment, an ac voltage Ein is applied across the terminal 2A 
connecting to the i-th number strip-shaped electrodes 44-1L, 44-3L,--and 
44-1R, 44-3R,--wherein i is an odd number and the terminal 2B connecting 
to the k-th number strip-shaped electrodes 44-2L, 44-4L,--and 44-2R, 
44-4R,--wherein k is an even number. The ac voltage Ein has a frequency of 
112 kHz. By applying the ac voltage to the strip-shaped electrodes, 
distortion is repeatedly produced through an electromechanical coupling 
factor k.sub.33 along a longitudinal axis of the cylindrical piezoelectric 
body 1. As a result, resonant longitudinal oscillation is generated in the 
piezoelectric body 1 in a direction of a longitudinal axis of the 
cylindrical piezoelectric body 1. The thus generated oscillation is of 
tertiary oscillation mode. That is, the end surfaces 1a and 1b of the 
cylindrical piezoelectric body 1 act as open ends, and thereby make loops 
of the oscillation. Supposing the cylindrical piezoelectric body 1 is 
divided into six sections, there are generated three nodal points of the 
oscillation between first and second sections, between third and fourth 
sections, and between fifth and sixth sections. 
The above mentioned resonant longitudinal oscillation produces voltages 
through the electromechanical coupling factor k.sub.33 between the 
electrode 5 and the strip-shaped electrode 44-1L and also between the 
electrode 5 and the strip-shaped electrode 44-1R. The thus produced 
voltages are obtained through the terminals 3A and 3B as an output voltage 
Eout. 
When the strip-shaped electrodes were designed to have a line width of 0.2 
mm, and the adjacent electrodes were designed to be spaced away from each 
other by 0.8 mm, the piezoelectric transformer in accordance with the 
instant embodiment could deal with electric power of about 2 W. The 
step-up ratio was about 20, which was lower than the step-up ratios in the 
first to third embodiments. However, if a load having a relatively low 
impedance (for instance, a cold cathode fluorescent light to be used for 
liquid crystal back light of a note type personal computer has an 
impedance of about 70 k.OMEGA. during turned on) is driven by the 
piezoelectric transformer in accordance with the first embodiment, a 
step-up ratio is reduced down to about 10. In contrast, if driven by a 
piezoelectric transformer in accordance with the fourth embodiment, the 
step-up ratio is not reduced, but kept to be at about 20. This is because 
a piezoelectric transformer in accordance with the fourth embodiment has 
lower output impedance than that of the first to third embodiments. 
In the instant embodiment, the maximum tensile stress is generated in the 
vicinity of the electrode 5. There was conducted a test for a sufficient 
number of piezoelectric transformers in accordance with the instant 
embodiment. In the test, after the piezoelectric transformers were treated 
in fabrication process with care which would be usually taken for treating 
ceramics, they were experimentally operated with electric power of about 5 
W. The result was that chipping never occurred in all of the tested 
piezoelectric transformers. 
The audible noises were below 25 dB at a distance of 5 cm away from the 
tested piezoelectric transformer, which poses no problem in practical use. 
As mentioned earlier, the three nodal points of oscillation are generated 
in a direction of a longitudinal axis of the piezoelectric body 1. Thus, 
by connecting the piezoelectric body 1 to an external terminal through 
lead wires at the nodal points, it is possible to readily support a 
piezoelectric transformer and enhance reliability in connection of a 
piezoelectric transformer to an external terminal through lead wires. In 
addition, as mentioned earlier, since a piezoelectric transformer in 
accordance with the instant embodiment has a lower output impedance, it is 
possible to have a higher step-up ratio for a load having a smaller 
impedance. 
Fifth Embodiment! 
FIG. 6 illustrates a piezoelectric embodiment in accordance with the fifth 
embodiment. In the above mentioned fourth embodiment illustrated in FIG. 
5, the strip-shaped electrodes 14-1 to 14-n in accordance with the first 
embodiment illustrated in FIG. 2 are applied to a piezoelectric 
transformer as electrodes to be formed in the first and second driven 
sections 42L and 42R. The same can be done for a piezoelectric transformer 
in accordance with the second embodiment illustrated in FIG. 3. 
As illustrated in FIG. 6, a piezoelectric transformer in accordance with 
the fifth embodiment has a cylindrical piezoelectric body 1 defining three 
sections in a direction of a longitudinal axis of the piezoelectric body 
1: a first driven section 52L including an end surface 1b of the 
cylindrical piezoelectric body 1; a second driven section 52R including 
the other end surface 1a of the cylindrical piezoelectric body 1; and a 
voltage generating section 53 sandwiched between the driven sections 52L 
and 52R. 
In each of the driven sections 52L and 52R, there are formed a pair of 
electrodes 54a and 54b equally spaced away from each other. Those 
electrodes 54a and 54b are the same as the electrodes 24a and 24b as 
illustrated in FIG. 3. 
An electrode 5 is wound around the cylindrical piezoelectric body 1 at the 
center of the voltage generating section 53. 
The polarization of the driven sections 52L, 52R and the voltage generating 
section 53 is accomplished in the same way as that of the second 
embodiment. 
The thus obtained piezoelectric transformer in accordance with the fifth 
embodiment provides the same advantages as those of the fourth embodiment. 
Sixth Embodiment! 
FIG. 7 illustrates a piezoelectric embodiment in accordance with the sixth 
embodiment. As illustrated in FIG. 7, a piezoelectric transformer in 
accordance with the sixth embodiment has a cylindrical piezoelectric body 
1 defining three sections in a direction of a longitudinal axis of the 
piezoelectric body 1: a first driven section 62L including an end surface 
1b of the cylindrical piezoelectric body 1; a second driven section 62R 
including the other end surface 1a of the cylindrical piezoelectric body 
1; and a voltage generating section 63 sandwiched between the driven 
sections 62L and 62R. 
In each of the driven sections 62L and 62R, there are formed a pair of 
spiral electrodes 64a and 64b equally spaced away from each other. Those 
spiral electrodes 64a and 64b are the same as the spiral electrodes 34a 
and 34b as illustrated in FIG. 4. 
An electrode 5 is wound around the cylindrical piezoelectric body 1 at the 
center of the voltage generating section 63. 
The polarization of the driven sections 62L, 62R and the voltage generating 
section 63 is accomplished in the same way as that of the third 
embodiment. 
The thus obtained piezoelectric transformer in accordance with the sixth 
embodiment provides the same advantages as those of the fourth embodiment. 
Seventh Embodiment! 
FIG. 8 illustrates a piezoelectric embodiment in accordance with the 
seventh embodiment. In the piezoelectric transformer in accordance with 
the first embodiment as illustrated in FIG. 2, the electrode 4 for the 
voltage generating section 13 is formed on the end surface 1a of the 
cylindrical piezoelectric body 1. In contrast, an electrode 5 for a 
voltage generating section is formed at a curved surface and adjacent to 
an end surface 1a of a cylindrical piezoelectric body 1. 
Comparing to a piezoelectric transformer in accordance with the first 
embodiment in which the electrode 4 is formed on the end surface 1a of the 
piezoelectric body 1, a piezoelectric transformer in accordance with the 
seventh embodiment shows a tendency that a step-up ratio becomes smaller 
for a shorter length of the piezoelectric body 1. However, when a 
piezoelectric transformer in accordance with the seventh embodiment is 
designed to have a length of 42 mm and a diameter of 2.5 mm, there is 
almost no difference in a step-up ratio between the first and seventh 
embodiment. The seventh embodiment provides an advantage that the 
electrodes may be formed by the smaller number of printing than the first 
embodiment with the result of reduction in fabrication costs. 
Eighth Embodiment! 
FIG. 9 illustrates a piezoelectric embodiment in accordance with the eighth 
embodiment. A piezoelectric transformer in accordance with the instant 
embodiment is different from the second embodiment as illustrated in FIG. 
3 in that an electrode 5 for a voltage generating section is formed at a 
curved surface and adjacent to an end surface 1a of a cylindrical 
piezoelectric body 1. Electrodes formed in a driven section are the same 
as the electrodes 24a and 24b in the second embodiment. The piezoelectric 
transformer in accordance with the eighth embodiment provides the same 
advantages as those of the seventh embodiment. 
Ninth Embodiment! 
FIG. 10 illustrates a piezoelectric embodiment in accordance with the ninth 
embodiment. A piezoelectric transformer in accordance with the instant 
embodiment is different from the third embodiment as illustrated in FIG. 4 
in that an electrode 5 for a voltage generating section is formed at a 
curved surface and adjacent to an end surface 1a of a cylindrical 
piezoelectric body 1. Electrodes formed in a driven section are the same 
as the spiral electrodes 34a and 34b in the third embodiment. The 
piezoelectric transformer in accordance with the ninth embodiment provides 
the same advantages as those of the seventh embodiment. 
Tenth Embodiment! 
FIG. 11 illustrates a support in accordance with an embodiment of the 
present invention. The illustrated support is for supporting a 
piezoelectric transformer in accordance with the first embodiment as 
illustrated in FIG. 2. 
The support includes a ring 36 having a greater diameter than a diameter of 
a cylindrical piezoelectric body 1 of the piezoelectric transformer, and 
electrically insulating, resilient silicone resin 37 sandwiched between an 
inner surface of the ring 36 and an outer surface of the piezoelectric 
body 1. The cylindrical piezoelectric body 1 is supported at the midpoint 
thereof by being inserted into the ring 36 with the silicone resin 37 
fixing the piezoelectric body 1 in place. The ring 36 is fixed to a 
housing 38 (partially illustrated) in which the piezoelectric transformer 
is entirely placed. A thin lead wire 6 is soldered to an end surface 1a of 
the cylindrical piezoelectric body 1 for therethrough taking an output 
voltage generated by the piezoelectric transformer. 
There was conducted a test for evaluating the above mentioned piezoelectric 
transformer fixed in the housing 38 with respect to transformation 
efficiency in comparison with a piezoelectric transformer not fixed in the 
housing. The result was that the transformation efficiencies were almost 
the same for both of the piezoelectric transformers. 
Any enclosure may be employed in place of the ring 36, unless the 
piezoelectric body 1 can be inserted into the enclosure. Similarly, any 
resilient, electrically insulating material may be used in place of the 
silicone resin 37. 
Eleventh Embodiment! 
FIGS. 12A and 12B illustrate a support in accordance with another 
embodiment. The support is for supporting the piezoelectric transformer in 
accordance with the first embodiment illustrated in FIG. 2. The 
piezoelectric transformer includes a piezoelectric body 1 having a 
diameter of 2.5 mm and a length of 4.2 mm. 
As illustrated in FIG. 12A, the support includes a package 15 including a 
pair of spacers 16A and 16B facing each other and a pair of electrode 
plates 17A and 17B facing each other. The spacers 16A, 16B and electrode 
plates 17A, 17B cooperate with each other to thereby form an almost square 
cross-section. The spacers 16A and 16B are made of electrically insulating 
material, and the electrode plates 17A and 17B are also made of 
electrically insulating material with a metal layer 17a and 17b covering 
an outer surface thereof. 
As illustrated in FIG. 12B, the electrode plates 17A and 17B are formed 
with a line of holes 18A and 18B, respectively. When the piezoelectric 
transformer is inserted into the package 15, the holes 18A are in 
alignment with every other strip-shaped electrodes, more specifically, 
k-th number electrodes 14-2, 14-4,--wherein k is an even number, whereas 
the holes 18B are in alignment with ever other strip-shaped electrodes, 
more specifically i-th number electrodes 14-1,14-3,--wherein i is an odd 
number. 
The holes 18A and 18B are filled with resilient, electrically conductive 
material such as silicone rubber 19. Thus, the i-th number strip-shaped 
electrodes 14-1, 14-3,--are electrically connected with one another 
through the silicon rubber 19 and the metal layer 17b wherein i is an odd 
number, whereas the k-th number strip-shaped electrodes 14-2, 14-4,--are 
electrically connected with one another through the silicon rubber 19 and 
the metal layer 17a wherein k is an even number. 
Lead wires 6A and 6B are electrically connected to the electrode plates 17A 
and 17B, respectively, and a lead wire 6C is electrically connected to an 
end surface of the piezoelectric body 1. An ac voltage is applied as input 
across the lead wires 6A and 6B, and as a result, a step-up voltage can be 
obtained as output through the lead wire 6C. 
There was conducted a test for evaluating the above mentioned piezoelectric 
transformer fixed in the package 15 with respect to transformation 
efficiency in comparison with a piezoelectric transformer not fixed in the 
package. The result was that the piezoelectric transformer in accordance 
with the instant embodiment had a slightly smaller transformation 
efficiency than the other, but which did not exert a harmful influence on 
practical use of the piezoelectric transformer. 
In the above mentioned embodiment, the package 15 is formed in a box shape, 
but it should be noted that the package may be formed in a cylinder into 
which a cylindrical piezoelectric body is jut fit. 
While the present invention has been described in connection with certain 
preferred embodiments, it is to be understood that the subject matter 
encompassed by way of the present invention is not to be limited to those 
specific embodiments. On the contrary, it is intended for the subject 
matter of the invention to include all alternatives, modifications and 
equivalents as can be included within the spirit and scope of the 
following claims. 
The entire disclosure of Japanese Patent Application No. 8-13670 on May 30, 
1996 including specification, claims, drawings and summa incorporated 
herein by reference in its entirety.