Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-04-09
2001-03-27
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S311000, C310S367000, C310S369000
Reexamination Certificate
active
06208065
ABSTRACT:
This application is based on patent application No. 10-119901 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the structure and process of forming of piezoelectric transducer, and an actuator using the piezoelectric transducer.
2. Description of Related Art
Actuators utilizing piezoelectric transducers are highly efficient in converting electrical energy to motive energy, and generating large amounts of motive energy though being compact and lightweight. In addition, the motive energy generated by the piezoelectric transducer can be easily regulated. All of these characteristics make actuators utilizing piezoelectric transducers ideal for use in positioning and moving driven members in cameras, test instruments and other precision equipment.
The piezoelectric transducer which serves as the drive source used in this kind of actuator is comprised of a plurality of piezoelectric elements laminated together. This configuration allows the largest possible physical displacement in the direction of piezoelectric element thickness to be obtained in response to an applied voltage.
FIG.
22
(
a
) is an oblique view showing the external structure of the piezoelectric transducer comprised of a plurality of piezoelectric elements laminated together. A piezoelectric transducer
100
is comprised of a plurality of individual piezoelectric elements
101
each being about 100 micrometers thick and provided on one surface with an electrode
102
. Every other electrode
102
(between facing piezoelectric elements) is connected to a line
103
as the positive terminal while the remaining electrodes
102
are connected to the line
104
as the negative terminal as shown in FIG.
22
(
b
). Since the thickness of the piezoelectric transducer changes as a voltage is applied between the positive and negative terminals, the changes in the thickness or displacement can be transmitted through an appropriate means to drive or position the driven member.
FIG. 23
is a cross-sectional view showing the actuator using the piezoelectric transducer comprised of a plurality of piezoelectric element units as described above.
FIG. 24
is a cross sectional view showing the friction coupling of the actuator.
In
FIG. 23
, the reference numeral
111
denotes a frame,
112
,
113
,
114
are support blocks and
115
is a drive shaft. The drive shaft
115
is supported by the support block
113
and the support block
114
to allow axial movement. One end of the piezoelectric transducer
100
is affixed to the support block
112
and affixed at the other end to the drive shaft
115
. The drive shaft
115
is supported to allow axial displacement (direction of arrow a and its opposite direction) in response to displacement in the direction of thickness of the piezoelectric transducer
100
.
The drive shaft
115
passes through a slider block
116
. An aperture
116
a
is formed, as shown in
FIG. 24
, in the lower part of the slider block
116
through which the drive shaft
115
passes and the lower half of the drive shaft
115
is thus exposed. In this aperture
116
a
, a pad
117
is fitted to engage with the lower half of the drive shaft
115
, and a protrusion
117
a
is formed in the lower section in the pad
117
(See FIG.
24
). The protrusion
117
a of the pad
117
is pressed upwards by a plate spring
118
and an upward force F is thus applied on the pad
117
to contact the drive shaft
115
.
A table
120
for placement of objects is secured to the slider block
116
with machine screws
121
.
In the above arrangement, the drive shaft
115
and slider block containing the pad
117
are press-contacted by the force F of the plate spring
118
and friction coupled.
The operation is described next. First of all, when a sawtooth waveform pulse having a gentle rising part and a steep falling part is applied to the piezoelectric transducer
100
, the gentle rising part of the drive pulse causes the piezoelectric transducer
100
to elongate, displacing in the direction of thickness, and the drive shaft
115
coupled to the piezoelectric transducer
100
also displaces slowly in the direction of the arrow “a”. The slider block
116
at this time friction coupled to the drive shaft
115
moves in the direction of the arrow “a” along with the drive shaft
15
due to the friction coupling force.
The steep falling part of the drive pulse causes the piezoelectric transducer
100
to contract, displacing in the direction of thickness, and the drive shaft
115
coupled to the piezoelectric transducer
100
also displaces swiftly in the opposite direction of the arrow “a”. The slider block
116
at this time friction coupled to the drive shaft
115
is effectively stopped in the current position and does not move, due to the cancelling out of the friction coupling force by the inertia of the slider block
116
. The slider block
116
and the table attached to the slider block
116
can be moved consecutively in the direction of the arrow “a” by means of consecutive application of drive pulses to the piezoelectric transducer
100
.
In order to move the slider block
116
and the table
120
in the opposite of the previous direction (opposite direction of arrow “a”), the sawtooth drive pulse waveform applied to the piezoelectric transducer
100
is changed and a drive pulse consisting of a steep rising part and a gentle falling part can then be applied to achieve movement in the opposite direction.
The above description also effectively takes into account that a sliding motion is added to the friction coupled surfaces between the slider block
116
and the drive shaft
115
whether moving in the direction of the arrow “a” or the opposite direction and objects moving in direction of the arrow “a” are also included due to the difference in drive times.
Among other configurations of the piezoelectric transducer is a piezoelectric transducer formed in hollow tubular shape of a single layer.
FIG. 25
is a cross sectional view showing one configuration of the hollow tubular shaped single layer piezoelectric transducer
134
. In
FIG. 25
, an electrode
136
and an electrode
137
are formed on the outer surface of the single layer, hollow tubular piezoelectric transducer
134
, and an electrode
138
is formed on the inner surface of the hollow cylinder.
The single layer, hollow tubular piezoelectric transducer
134
is supported by support members
132
,
133
installed on the right and left of a mount
131
. A slider
135
is friction coupled to the hollow tubular piezoelectric transducer
134
by an appropriate amount of frictional force. A plug
133
a
is installed to fit in with one end of the piezoelectric transducer
134
and this plug
133
a
screws into the support member
133
so that the piezoelectric transducer
134
is secured and supported by the mount
131
.
In this configuration, a first electrode section comprised of an electrode
136
and an electrode
138
; and a second electrode section comprised of an electrode
137
and an electrode
138
, are both polarized beforehand in the same radial direction. When sawtooth wave pulses of mutually reverse polarities are applied to the first electrode section and the second electrode section while in this state, an elongation displacement occurs at the first electrode section and a contraction displacement occurs at the second electrode section during the gentle rising part of the sawtooth waveform pulse, and the slider
135
can move in the direction of the arrow “a”. Further, on the steep falling part of the sawtooth waveform pulse a sudden contraction displacement occurs at the first electrode section and a sudden elongation displacement occurs at the second electrode section however the inertia of the slider
135
cancels out the force of the frictional coupling with the piezoelectric transducer
134
and there is no sliding movement on their surfaces. Thus by transmitting the movement of the slider
135
to the drive section of a transducer by a suita
Dougherty Thomas M.
Minolta Co. , Ltd.
Sidley & Austin
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