Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-06-04
2003-05-06
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S323120, C310S323160
Reexamination Certificate
active
06559574
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stacked piezoelectric element for use as a stacked electro-mechanical energy conversion element, which has a configuration particularly suitable for miniaturization.
2. Related Background Art
Conventionally, a piezoelectric material having an electro-mechanical energy conversion function has been used as various types of piezoelectric elements and piezoelectric devices. Particularly, regarding these piezoelectric elements and piezoelectric devices, a recent tendency has been to use, for example, those having a structure constituted by laminating a large number of single plate-like sheets formed by ceramics.
This is because, in contrast to a single plate-like piezoelectric element, through lamination, a large deformation distortion as well as a large power can be obtained with a low applied voltage. In addition, a sheet formation method and a manufacturing method of lamination are so generalized that a thickness of one layer to be laminated can be made thinner, thereby making it easy to obtain the piezoelectric element of a small size and a high performance.
For example, a stacked piezoelectric element for use in a vibration wave motor as a vibration wave drive device is proposed in U.S. Pat. No. 6,046,526 or U.S. Pat. No. 5,770,916. In addition, a large number of stacked piezoelectric elements for use in a vibration gyro and a piezoelectric transformer are also proposed.
With respect to the stacked electro-mechanical elements used for such a variety of applications, those having an electrode area formed in a material having the electro-mechanical energy conversion function, for example, those having a structure constituted by superposing the electrode in a plurality of layers which are formed of an electrode material and disposed on the surface of the piezoelectric ceramics (hereinafter referred to as the internal electrode) are used.
In general, as an inter layer wiring line for connecting one internal electrode of the layers to another having a different laminated state, an electro-conductive film (hereinafter referred to as the external electro-conductive film) used to form a connection is disposed on an outer periphery or an inner periphery of the stacked piezoelectric element, or a hole is disposed inside the layer of a piezoelectric layer in which the electrode material is embedded, thereby defining a through-hole (a via hole).
FIGS. 5A and 5B
and
FIGS. 6A and 6B
show the conventional stacked piezoelectric element described in U.S. Pat. No. 5,770,916. In
FIGS. 5A and 5B
, a disc-shaped stacked piezoelectric element
110
, in the center portion of which a penetration hole is formed, is constituted by the uppermost piezoelectric sheet
102
and a plurality of piezoelectric sheets
112
. In one surface (hereinafter referred to as a first surface) of each of a plurality of piezoelectric layers (sheets)
112
constituting the stacked piezoelectric element, there are formed an internal electrode
113
. This internal electrode
113
is constituted by an internal electrode pattern having four divided structures which are mutually non-conductive, and a plurality of piezoelectric sheets
112
are laminated in such a manner that the phases of the divided patterns of the internal electrodes
113
correspond to each other. In the outer peripheral portion of each divided pattern of the internal electrode
113
, there is formed a connecting pattern
103
a
and this connecting pattern
103
a
reaches the outer peripheral end of the piezoelectric sheet
112
. At this time, the connecting pattern
103
a
is located at the same phase in every other piezoelectric sheet
112
.
By an external electro-conductive film
114
which is disposed on the outer peripheral surface of the laminated piezoelectric sheet, the connecting pattern
103
a
of every other piezoelectric sheet
112
is mutually communicated. In the uppermost piezoelectric sheet
102
, a surface electrode (a terminal pattern)
115
is formed on its outer peripheral end and communicated with the external electro-conductive film
114
.
On the other hand, the stacked piezoelectric elements of
FIGS. 6A and 6B
obtain communications among laminated piezoelectric layers (sheets) utilizing through-holes. On the surface of each piezoelectric sheet
112
constituting the stacked piezoelectric element
111
, there is disposed the internal electrode
113
constituted by the four divided structures, and in the vicinity of the inner peripheral side of each piezoelectric sheet, there are formed through-holes
116
as illustrated in the drawing by black dots. Of the through-holes
116
, there are those having communications with the internal electrodes
113
and those having no communications, and in this case, they are mutually located at positions shifted 90 degree in phase. The piezoelectric sheets
112
are laminated in such a manner that the internal electrodes
113
have 90 degree phase difference for every other sheet. In this way, the through-holes
116
located in the same phase are in a state of being alternatively superposed with those having communications with the internal electrodes
113
of the piezoelectric sheets
112
and those not having communications. In every odd number of the piezoelectric sheets
112
, internal electrodes which communicate via through-holes
116
are aligned with one another in the axial direction of the stacked piezoelectric element, and in every even number of the piezoelectric sheets
112
, internal electrodes which communicate with the through-holes
116
are aligned with one another in the axial direction of the stacked piezoelectric element. In this way, through-holes
116
which communicate with the internal electrodes
113
disposed in every odd number of the piezoelectric sheets
112
are aligned and connected with the non-communicating through-holes
116
of every even number of sheets. Similarly, through-holes
116
which do not communicate with odd numbered sheets are aligned with through-holes
116
which do communicate with even numbered sheets. Each through-hole
116
exposes the end portion of the through hole
116
at the uppermost piezoelectric sheets
102
of the stacked piezoelectric element
111
to form a surface electrode
117
.
The stacked piezoelectric elements of
FIGS. 5A and 5B
and
FIGS. 6A and 6B
thus constituted are subjected to a polarization process and exhibit piezoelectric efficiencies.
FIG. 7
is a view incorporating the stacked piezoelectric element
110
or
111
into a vibration body
120
constituting a vibration wave motor as a bar-shaped vibration wave driving device. The stacked piezoelectric element
110
(
111
) is sandwiched between metal parts
121
,
122
which are elastic members of the vibration body
120
by a bolt
123
through a wiring substrate
118
to be connected with an external power source. The wiring substrate
118
is electrically connected to each surface electrode
115
(
117
) of the stacked piezoelectric element
110
(
111
) and generates a driving vibration attributable to the synthesis of two bending vibrations orthogonal to the vibration body
120
. By this driving vibration, a rotor
132
which is brought into press contact with an elastic member
121
by a spring
130
and a spring supporting body
131
is frictionally driven, so that a driving power is output by a gear
133
working as an output member integrally rotating with the rotor
132
.
It is to be noted that the stacked piezoelectric element
111
which uses the whole of through-holes for connecting the internal electrodes of
FIGS. 6A and 6B
has already been mass-produced and come in practice as a motor to be used for the auto-focus of camera lenses incorporated into the vibration wave motor as shown in FIG.
7
.
The stacked piezoelectric elements of the external electrode connection system as shown in
FIGS. 5A and 5B
and the through-hole connection system as shown in
FIGS. 6A and 6B
are constituted by the electrode portions (patterns) in which the internal electrodes
113
Budd Mark O.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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