Electricity: motive power systems – Nonmagnetic motor
Reexamination Certificate
2003-07-16
2004-10-19
Tamai, Karl (Department: 2834)
Electricity: motive power systems
Nonmagnetic motor
C310S309000
Reexamination Certificate
active
06806661
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic actuator for driving a slider or a movable section with an electrostatic force and a method of driving the same, particularly, to an electrostatic actuator having an improved simple structure and capable of driving the slider or the movable section with a high accuracy and a method of driving the same.
The electrostatic actuator for driving a slider or a movable section has already been disclosed in some publications, e.g., Japanese Patent Disclosure (Kokai) No. 8-140367, and “Electrostatic Linear Microactuator Mechanism, JOURNAL OF LIGHTWAVE TECHNOLOGY, Vol. 17, No. 1, January 1999, IEEE”. The actuator disclosed in these publications comprises an array of electrodes as shown in FIG.
1
. In this electrostatic actuator, a slider or a movable section
102
is arranged slidable forward as denoted by an arrow
101
or backward between two stators
103
A and
103
B arranged to face each other. An electrode section
104
is provided on the slider
102
. Two systems of stator electrodes
106
A and
106
C to which voltage is applied at different timings are alternately arranged on the stator
103
A. Likewise, two systems of electrodes
106
B and
106
D to which voltage is applied at different timings are arranged on the other stator
103
B. The electrodes
106
A to
106
D provided on the stators
103
A,
103
B and the electrode section
104
of the slider
102
are substantially equal to each other in the pitch and the electrode width. Also, the electrodes
106
A,
106
C of the stator
103
A and the electrodes
106
B,
106
D of the stator
103
B are arranged such that the phase of the arrangement is shifted by ½.
If a voltage is applied from a voltage source (not shown) to the electrode
106
A in the electrostatic actuator of the particular construction, an electrostatic force, i.e., Coulomb force, is generated between the electrode
106
A and the electrode section
104
, with the result that the slider
102
is attracted toward the stator
103
A such that the electrode
106
A and the electrode section
104
are allowed to faced to each other. Then, when the switching circuit (not shown) for supplying a voltage is switched to change the electrode to which a voltage is supplied from the electrode
106
A to the electrode
106
B so as to supply a voltage to the electrode
106
B, the slider
102
is attracted toward the other stator
103
B such that the electrodes
106
B and the electrode section
104
are allowed to faced to each other. Also, when the switching circuit is switched to change the electrode to which a voltage is supplied from the electrode
106
B to the electrode
106
C so as to supply a voltage to the electrode
106
C, the slider
102
is attracted toward the stator
103
A again such that the electrodes
106
C and the electrode section
104
are allowed to faced to each other. Further, when the switching circuit is switched to change the electrode to which a voltage is supplied from the electrode
106
C to the electrode
106
D so as to supply a voltage to the electrode
106
D, the slider
102
is attracted toward the stator
103
B again such that the electrodes
106
D and the electrode section
104
are allowed to faced to each other. As described above, if a voltage is applied successively to the electrodes
106
A,
106
B,
106
C and
106
D, the slider
102
is vibrated microscopically between the stators
103
A and
103
B and is macroscopically driven in the forward direction as denoted by the arrow
101
in FIG.
1
. If the order of applying a voltage to the electrodes is reversed such that the voltage is applied to the electrodes
106
D,
106
C,
106
B and
106
A in the order mentioned, the slider
102
is driven in the backward direction opposite to the forward direction denoted by the arrow
101
in FIG.
1
.
In the electrostatic actuator described above, it is necessary for the pair of stators
103
A and
103
B to be aligned with a high accuracy. It is also necessary for the electrodes of the same width to be formed equidistantly with a high accuracy in the stators
103
A,
103
B. Naturally, a sufficient time and labor are required for manufacturing the parts of the electrostatic actuator and for assembling these parts with a high accuracy, leading to a high manufacturing cost of the actuator. This problem of the high manufacturing cost must be overcome for realizing a mass production of the actuator.
A method of applying voltage and the operating principle of the conventional electrostatic actuator will now be described with reference to FIG.
1
. Incidentally, those members of the actuator, which are substantially same as those shown in
FIG. 1
are denoted by the same reference numerals in
FIG. 2
for avoiding the overlapping description.
As described above with reference to
FIG. 1
, if a voltage is applied successively to the electrodes
106
A to
106
D provided on the stators
103
A and
103
B, the slider
102
is driven so as realize a linear movement on a macroscopic level. In the electrostatic actuator shown in
FIG. 2
, the electrodes
106
A and
106
B are covered with a dielectric film
105
so as to prevent these electrodes
106
A,
106
B from the insulation breakdown, as disclosed in Japanese Patent Disclosure No. 8-140367 referred to previously.
If a voltage is applied first to the electrode
106
A as shown in
FIG. 2
, dielectric polarization
107
is generated in a dielectric film
105
covering the electrode
106
A. Then, if a voltage is applied to the electrode
106
B, the slider
102
is attracted toward the other stator
103
B so as to be driven such that the electrode section
104
is allowed to face the electrode
106
B. It should be noted, however, that the component of the dielectric polarization generated in the dielectric film
105
mounted on the electrode
106
A produces the function of keeping the slider
102
attracted toward the stator
103
A. The component of the force produced by the dielectric polarization
107
is very small in terms of the potential level. However, since the distance between the stator
103
A and the electrode section
104
of the slider
102
is short, it is possible for the force generated by the dielectric polarization
107
not to be negligible as a force for inhibiting the movement of the slider
102
. This is based on the fact that the electrostatic force is inversely proportional to the square of the distance between the electrodes. Under the circumstances, the driving of the slider
102
tends to be unstable in the conventional electrostatic actuator. It should also be noted that the degree of the charge leakage in the dielectric film
105
, i.e., the time for the dielectric polarization to disappear, is not constant, which also provides a cause of the failure for the movement of the slider
102
to be made constant.
As described above, in the conventional electrostatic actuator, it is necessary to align accurately the two stators
103
A and
103
B so as to provide accurately a desired phase of arrangement of these two stators. It is also necessary to form accurately the electrodes facing the two surfaces of the slider or movable element
102
. It follows that a long time and much labor are required for assembling the actuator, leading to a high manufacturing cost. In other words, serious problems must be solved before the mass production of the actuator is realized.
It should also be noted that, in the conventional electrostatic actuator, the driving operation of the slider
102
tends to become unstable because of the influence produced by the dielectric polarization taking place in the dielectric film covering the electrode.
What should also be noted is that the degree of the charge leakage in the dielectric film
105
, i.e., the time for the dielectric polarization to disappear, is not constant, which also provides a cause of the failure for the movement of the slider
102
to be made constant.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an electrostatic actuator, which permits im
Kasahara Akihiro
Koga Akihiro
Sekimura Masayuki
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