Piezoelectric transformer

Details Piezoelectric transformer Piezoelectric transformer

1999-11-17

2001-09-11

Dougherty, Thomas M. (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

Reexamination Certificate

active

06288479

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a piezoelectric transformer; and, more particularly, to a center-driving type piezoelectric transformer.
BACKGROUND OF THE INVENTION
FIG. 8
shows an exemplary piezoelectric transformer of a prior art, e.g., a center-driving type piezoelectric transformer disclosed in Japanese Patent Laid-Open No.9-74236 which has a driving section located at a center portion thereof. As shown in
FIG. 8
, input electrodes
51
and
52
are placed on top and bottom surfaces of a center portion of a sheet or plate type, e.g., long-plate-shaped, piezoelectric member
50
when viewed from top, respectively, wherein the input electrodes
51
and
52
face with each other. The center portion of the piezoelectric member
50
disposed between the input electrodes
51
and
52
are polarized in a thickness direction, wherein the center portion forms a driving section of the piezoelectric transformer. Output electrodes
55
and
56
are formed on right and left sides of the piezoelectric member
50
, respectively.
Right and left end portions of the piezoelectric member
50
are polarized in opposite longitudinal directions with each other, wherein the end portions form power generating sections of the piezoelectric transformer. A ratio of a length L
2
of the driving section to a longitudinal length L
1
of the piezoelectric member
50
in the longitudinal direction, i.e., L
2
/L
1
, ranges from 0.3 to 0.6. With this configuration, a larger voltage-rise ratio is obtained.
However, in the prior art piezoelectric transformer, no consideration is given to the thickness of the piezoelectric member incorporated therein. Experimental data clearly indicates that the thickness of the piezoelectric member considerably affects the efficiency, i.e., a ratio of an output power to an input power, thereof. It is preferable to have in a piezoelectric transformer an enhanced efficiency, an increased output power and a large voltage-rise ratio simultaneously.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to provide a piezoelectric transformer with a consideration given to the thickness of a piezoelectric member incorporated therein. It is another object of the present invention to provide a piezoelectric transformer exhibiting an enhanced efficiency, an increased output power and a large voltage-rise ratio thereof simultaneously.
In order to achieve the above-mentioned object, in accordance with one aspect of the present invention, there is provided a piezoelectric transformer comprising: a long-plate-shaped piezoelectric member being polarized in a thickness direction and a longitudinal direction; and input electrodes and output electrodes mounted on the piezoelectric member, wherein a thickness ratio LC/LA of the piezoelectric member ranges from 0.01 to 0.06, LC and LA being a thickness and a longitudinal length of the piezoelectric member, respectively. More preferably, the ratio LC/LA ranges from 0.02 to 0.05. In another aspect of the present invention, an electrode length ratio LB/LA of the piezoelectric member ranges from 0.6 to 0.9, LB being a length of the input electrodes in the longitudinal direction. More preferably, the ratio LB/LA ranges from 0.7 to 0.8.
One important feature of the present invention is that the piezoelectric may include a plurality of thin piezoelectric sheets, each of the input electrodes, e.g., input electrode patterns, being formed on top of a center portion of each piezoelectric sheet; outer electrodes are formed on two opposite sides of the center portion of the piezoelectric member; and the input electrodes are alternatively connected to the outer electrodes.


REFERENCES:
patent: 5424602 (1995-06-01), Sato et al.
patent: 5751092 (1998-05-01), Abe
patent: 5763983 (1998-06-01), Huang
patent: 5777425 (1998-07-01), Ino et al.
patent: 5872419 (1999-02-01), Hall et al.
patent: 7-221359 (1995-08-01), None
patent: 8-213666 (1996-08-01), None
patent: 11-145528 (1999-05-01), None

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