Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-03-28
2002-11-19
Sircus, Brian (Department: 2839)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S317000, C361S152000
Reexamination Certificate
active
06483226
ABSTRACT:
This application is based on patent applications Hei.11-89626 and 11-271184 filed in Japan, the contents of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an impact actuator using piezoelectric device as a driving source and an equipment such as a camera or a binocular using the impact actuator.
2. Description of the Related Art
An impact actuator using a piezoelectric device as a driving source is conventionally known. In the impact actuator, a driven member is movably coupled with a rod shaped driving member in an axial direction of the driving member. A piezoelectric device is fixed on an end of the driving member in a manner so that a direction of polarization of the piezoelectric device coincides with an axial direction of the driving member.
FIG. 11
shows a schematic configuration of a conventional impact actuator.
FIGS. 12 and 13
show examples of circuit diagram of a slow charging circuit in FIG.
11
.
FIG. 14
shows an example of a slow discharging circuit in FIG.
11
.
As can be seen from
FIG. 11
, the conventional impact actuator
100
comprises a rod shaped driving member
101
, a driven member
102
, a laminated piezoelectric device
103
and a driving circuit
104
. The driven member
102
is coupled with the driving member
101
by a predetermined friction force. When a force acting on the driven member
102
is larger than the friction force, the driven member
102
can be slid on the driving member
101
in an axial direction thereof. An object such as the taking lens to be driven is fixed on the driven member
102
. The piezoelectric device
103
is fixed on a base end
101
b
of the driving member
101
in a manner so that a direction of polarization of the piezoelectric device
103
coincides with the axial direction of the driving member
101
. A pair of electrodes
103
a
and
103
b
are formed on both ends of the piezoelectric device
103
. The electrode
103
b
is grounded and the electrode
103
a
is connected to the driving circuit
104
.
The driving circuit
104
comprises a forward driver
105
, a backward driver
106
and a controller
107
for controlling the drivers
105
and
106
. The forward driver
105
drives the actuator so as to move the driven member
102
toward an open end
101
a
of the driving member
101
. Hereinafter, the direction toward the open end
101
a
of the driving member
101
is called “forward”. The backward driver
106
drives the actuator so as to move the driven member
102
toward the base end
101
b
of the driving member
101
. Hereinafter, the direction toward the base end
101
b
of the driving member
101
is called “backward”.
In the conventional impact actuator
100
relatively moves the driven member
102
with respect to the driving member
101
by utilizing the difference of the friction forces between the driving member
101
and the driven member
102
when the driving member
101
is vibrated by different speed. The friction force between the driven member
102
and the driving member
101
becomes smaller when the driving member
101
moves quickly, and it becomes larger when the driving member
101
moves slowly. Thus, the driven member
102
moves with the driving member only when the driving member
101
moves slowly. When the driving member
101
repeats the slow forward movement and the quick backward movement in the forward driving operation, the driven member
102
relatively moves forward (forward driving operation). When the driving member
101
repeats the quick forward movement and the slow backward movement in the backward driving operation, the driven member
102
relatively moves backward (backward driving operation).
The forward driver
105
comprises a slow charger
105
a
and a quick discharger
105
b.
The backward driver
106
comprises a quick charger
106
a
and a slow discharger
106
b.
The slow charger
105
a
and the quick charger
106
a
respectively apply a voltage of a power supply in the direction of polarization to the piezoelectric device
103
for expanding the piezoelectric device
103
in the axial direction of the driving member
101
. The slow charger
105
a
is a constant current charging circuit shown in
FIG. 12
or
FIG. 13
for restricting a charging speed of the electric charge by controlling a value of a charging current.
FIG. 12
shows a constant current circuit configured by a pnp type transistor Tr
1
, a Zener diode ZD and resisters r
1
to r
3
. The resisters r
1
and r
2
are biasing resisters of the transistor Tr
1
. The Zener diode ZD is connected in parallel with the resister r
2
which is connected to a base of the transistor Tr
1
. By such a configuration, a base voltage of the transistor Tr
1
is controlled at a fixed value by the Zener diode ZD, so that a voltage drop by the resister r
1
can be stabilized. As a result, a collector current of the transistor Tr
1
is controlled to be constant.
FIG. 13
shows another constant current circuit configured by a pnp type transistor Tr
1
, an npn type transistor Tr
2
and resisters r
1
and r
3
. A parallel circuit of the resistor r
2
and the Zener diode ZD in
FIG. 12
is replaced by the transistor Tr
2
. A base and a collector of the transistor Tr
2
are respectively connected to an emitter and a base of the transistor Tr
1
. An emitter of the transistor Tr
2
is connected to a power supply Vp. A base voltage of the transistor Tr
1
is controlled to be a constant value by the transistor Tr
2
, so that a voltage drop by the resister r
1
can be stabilized. As a result, a collector current of the transistor Tr
1
is controlled to be constant.
The quick discharger
105
b
and the slow discharger
106
b
respectively apply a voltage in a reverse direction of polarization to the piezoelectric device
103
for contracting the piezoelectric device
103
. The slow discharger
106
b
is a constant current discharging circuit shown in
FIG. 14
for restricting a discharging speed of the electric charge by controlling a value of a discharging current.
FIG. 14
shows a constant current circuit configured by an npn type transistor Tr
3
, a Zener diode ZD and resisters r
4
and r
5
. The resister r
4
restricts the discharging current. A voltage of a base of the transistor Tr
3
is controlled to be a predetermined value by the Zener diode ZD, so that a voltage drop by the resister r
4
can be stabilized. As a result, an emitter current flowing the resister r
4
, which is the discharging current, is controlled to be constant.
The controller
107
controls the operations of the forward driver
105
and the backward driver
106
. When the driven member
102
is to be moved forward, the controller
107
alternately drives the slow charger
105
a
and the quick discharger
105
b.
When the driven member
102
is to be moved backward, the controller
107
alternately drives the quick charging circuit
106
a
and the slow discharger
106
b.
When the slow charger
105
a
and the quick discharger
105
b
are alternately driven in a forward driving operation, the piezoelectric device
103
repeats slow expansion and quick contraction alternately. Thus, the driving member
101
repeats a slow forward movement and a quick backward movement. On the contrary, when the quick charger
106
a
and the slow discharger
106
b
are alternately driven in a backward driving operation, the piezoelectric device
103
repeats quick expansion and slow contraction alternately. Thus, the driving member
101
repeats a quick forward movement and a slow backward movement.
Accordingly, the driven member
102
relatively moves forward with respect to the driving member
101
in the forward driving operation, and the driven member
102
relatively moves backward with respect to the driving member
101
in the backward driving operation.
When the impact actuator is used as an actuator for moving an optical lens system of a handy equipment such as camera or a binocular, it is preferable that the driving circuit is simple and small with regard to lightening and downsizing
Minolta Co. , Ltd.
Sidley Austin Brown & Wood LLP
Sircus Brian
Zarroli Michael C.
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