US 6,274,966 B1Granted

Piezoelectric actuator

AssigneeMurata Manufacturing Co., Ltd.

InventorsYoshiaki Kohno, Hiroshi Nakatani, Toshiaki Kaji

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Abstract

A piezoelectric actuator is constructed to have a displacement value caused by bending to be added to a usual d31 component displacement, thereby increasing the total amount of displacement of the actuator. The actuator includes an actuator body having a layered structure of piezoelectric layers and internal electrodes, and external electrodes disposed on an external surface of the actuator body at both ends thereof. One of the outermost piezoelectric layers is made piezoelectrically active as a result of making an extension portion of the first external electrode, through the one of the outermost piezoelectric layers, face the inner electrodes, to have a polarity which is different from that of the extension portion, while a second of outermost piezoelectric layers is made piezoelectrically inactive as a result of either making an extension portion of the second external electrode facing, through the second of the outermost piezoelectric layers, the inner electrodes, to have a polarity which is identical to that of the extension portion of the second external electrode or as a result of not forming an extension portion on the outer electrode.

Claims20

Dependent claims

A d31 type piezoelectric actuator, comprising:

an actuator body having a laminated structure including a plurality of piezoelectric layers and a plurality of inner electrodes disposed between said piezoelectric layers, said actuator body having a first major surface, a second major surface, a first end surface and a second end surface, said first major surface and said second major surface being defined by outwardly facing major surfaces of two of the plurality of piezoelectric layers which are outermost layers among the piezoelectric layers, said first end surface and said second end surface being defined by the end surfaces of said piezoelectric layers, said actuator body including a piezoelectrically active region;
a first external electrode and a second external electrode provided on at least said first end surface and said second end surface, respectively;
said inner electrodes including first inner electrodes connected to said first external electrode at said first end surface and second inner electrodes connected to said second external electrode at said second end surface, said first inner electrodes and said second inner electrodes being alternately disposed in a direction in which said first and said second inner electrodes are laminated to each other so at to define said active region;
said first external electrode having an extension portion which extends to said first major surface;
and
said second inner electrodes facing said extension portion of said first external electrode in said piezoelectrically active region through said piezoelectric layer, which is the outermost layer at a location of said first major surface, whereby said piezoelectric layer at said location of said first major surface and at an area of said active region is piezoelectrically active, and said second inner electrode which is outermost at a location of said second major surface has the same polarity as said second external electrode such that said piezoelectric layer, which is the outermost layer at a location of said second major surface and at said area of said active region, is piezoelectrically inactive.

3 more elements

A piezoelectric actuator, comprising:

an actuator body including a plurality of piezoelectric layers and inner electrodes and having a first major surface, a second major surface, a first end surface and a second end surface, said first major surface and said second major surface being defined by outwardly facing major surfaces of two of the plurality of piezoelectric layers which are outermost layers among the piezoelectric layers, said first end surface and said second end surface being defined by the end surfaces of said piezoelectric layers, said actuator body including a piezoelectrically active region;
a first external electrode and a second external electrode provided on at least said first end surface and said second end surface, respectively;
wherein
one of said piezoelectric layers which is the outermost layer at a location of said first major surface is piezoelectrically active and one of said inner electrodes which is outermost at a location of said second major surface has the same polarity as said second external electrode such that another of said piezoelectric layers which is the outermost layer at a location of said second major surface is piezoelectrically inactive at an area of said active region.

1 more element

A piezoelectric actuator, comprising:

an actuator body including a plurality of piezoelectric layers and a plurality of inner electrodes and having a first major surface, a second major surface, a first end surface and a second end surface, said first major surface and said second major surface being defined by outwardly facing major surfaces of two of the plurality of piezoelectric layers which are outermost layers among the piezoelectric layers, said first end surface and said second end surface being defined by the end surfaces of said piezoelectric layers, said actuator body including a piezoelectrically active region, said active region having at least one of said outermost layers being piezoelectrically inactive in an area of said active region;
a first external electrode and a second external electrode provided on at least said first end surface and said second end surface, respectively;
wherein
said first end of said actuator body having said first external electrode disposed thereon is a free end and said second end of said actuator body having said second external electrode disposed thereon is a fixed end which is attached to a fixing member, said second external electrode including an extension portion which extends to said second major surface of said actuator body adjacent the first end of said actuator body, and
one of said plurality inner electrodes which is outermost at a location of said second major surface has the same polarity as said second external electrode such that the at least one of said outermost layers is piezoelectyrically inactive in an area of said active region.

2 more elements

Dependencies are inferred from the claim text.