Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1998-06-02
2001-02-13
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S323020
Reexamination Certificate
active
06188161
ABSTRACT:
This application is based on application No. Hei 9-143998 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a driving apparatus that uses as a drive source a member that expands and contracts, and more particularly, to a driving apparatus that employs an electromechanical transducer such as a piezoelectric element, e.g., to a driving apparatus used for the precision driving of an X-Y drive table, a camera image recording lens, or a probe of a scanning tunneling electron microscope.
2. Description of the Related Art
Conventional examples of a driving apparatus using a piezoelectric element include driving apparatus
10
a
in which movable unit
20
a
moves along shaft
14
, as shown in
FIGS. 1 through 3
, and driving apparatus
10
b
in which movable unit
20
b
moves along guide groove
18
, as shown in
FIGS. 4 through 6
. In these driving apparatuses
10
a
and
10
b
, an elastic deforming mechanism is constructed by pressing protrusion
24
a
or
25
a
of plate spring
24
or
25
, which is a friction member connected to one end of piezoelectric element
22
, against the outer surface of shaft
14
or against the inner surface of guide groove
18
, such that a frictional force may be created. A driving apparatus of the type in which the friction member has an elastic deforming mechanism which creates frictional force is superior to a driving apparatus of the type in which a frictional force is created by applying external force to the friction member by means of a spring member, as shown in U.S. Pat. No. 5,589,723, in that the construction may be simplified.
In either driving apparatus
10
a
or
10
b
, the elastic deformation stress vector that occurs during the elastic deformation of protrusion
24
a
or
25
a
of plate spring
24
or
25
runs in the directions indicated by bi-directional arrow
82
or
84
in
FIG. 3
or
6
, where stress is applied that has a component that works in the directions of expansion and contraction of piezoelectric element
22
, as shown by bi-directional arrow
80
. In other words, deflection occurs in plate spring
24
or
25
, the friction member, in the directions of expansion and contraction of piezoelectric element
22
, between the area that is fixed to piezoelectric element
22
and the area that is in frictional contact with shaft
14
or guide groove
18
, and plate spring
24
or
25
elastically deforms in expansion and contraction directions
80
of piezoelectric element
22
.
Therefore, if the frequency of the pulse voltage that is applied to piezoelectric element
22
is increased in order to move movable unit
20
a
or
20
b
of driving apparatus
10
a
or
10
b
at a high rate of speed, the change in position that occurs at one end
22
a
of piezoelectric element
22
can no longer be communicated to the frictional contact point via plate spring
24
or
25
in the same manner as before.
FIGS. 7 and 8
are graphs that show the transfer function G=Y/X, i.e., the relationship between the transfer of the change in position X of piezoelectric element
22
and the change in position Y of the frictional contact point between friction member
24
or
25
and shaft
14
or groove
18
. In other words, as shown in
FIGS. 7 and 8
, when the frequency increases, the gain decreases and the phase changes. Therefore, as shown in
FIG. 9
, with conventional driving apparatuses
10
a
and
10
b
, when the frequency increases to a certain level, the drive speed of movable units
20
a
and
20
b
decreases, as a result of which the drive speed cannot be increased by increasing the frequency.
SUMMARY OF THE INVENTION
The technological issue to be resolved by the present invention, therefore, is to improve the frequency characteristic of the transfer function governing the relationship between the change in position of the piezoelectric element and the change in position of the friction member's frictional contact point, so as to provide a driving apparatus capable of high speed driving in a high frequency range.
The present invention provides a driving apparatus having the following construction in order to resolve the technological issue described above.
The driving apparatus comprises (i) an electromechanical transducer that is connected to a drive pulse generating means and that expands and contracts, (ii) a first unit that is either fixed or movable and that is connected to one expansion end of said electromechanical transducer, (iii) a friction member that is connected to the other expansion end of said electromechanical transducer, and (iv) a second unit that is either movable or fixed that comes into frictional contact with said friction member, wherein said friction member has an elastic deforming mechanism that elastically presses against and comes into frictional contact with said second unit, said electromechanical transducer is expanded or contracted by means of said drive pulse generating means such that it drives said movable unit in a prescribed direction relative to said fixed unit, and said elastic deforming mechanism is constructed such that its elastic deformation stress vector vertically crosses the directions of expansion and contraction of said electromechanical transducer.
In the construction described above, the fixed unit is fixed and the movable unit may move relative to the fixed unit. In the driving apparatus, the electromechanical transducer slowly changes its position in a first direction and said second unit which is either movable or fixed, changes its position in the first direction due to the electrostatic friction between itself and the friction member, but when the electromechanical transducer suddenly changes its position in a second direction, the inertial force of the second unit overcomes the frictional force between itself and the friction member, causing the second unit to slip, as a result of which only the friction member returns to the original position, for example. Step driving of the driving apparatus can be achieved by repeating this process. Where the movable unit is fixed to one expansion end of the electromechanical transducer, to perform driving it is necessary for the mass of the movable unit to be smaller than the mass of the friction member that is fixed to the other expansion end of the electromechanical transducer.
Using the construction described above, the elastic deforming mechanism elastically deforms in directions that are perpendicular to the directions of expansion and contraction of the electromechanical transducer and does not deform in directions that are parallel to said directions of expansion and contraction. Consequently, the change in position of the electromechanical transducer caused by its expansion and contraction may be directly communicated to the frictional contact point of the friction member even when the driving frequency applied to the electromechanical transducer increases.
Therefore, the frequency characteristic of the function governing the transfer of the change in position of the piezoelectric element to the change in position of the friction member's frictional contact point may be improved and high-speed driving in the high frequency range becomes possible.
These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention.
REFERENCES:
patent: 3684904 (1972-08-01), Galutva et al.
patent: 3902084 (1975-08-01), May, Jr.
patent: 3902085 (1975-08-01), Bizzigotti
patent: 4219755 (1980-08-01), O'Neill et al.
patent: 4408832 (1983-10-01), Hartman et al.
patent: 4570096 (1986-02-01), Hara et al.
patent: 4736131 (1988-04-01), Fujimoto
patent: 4857791 (1989-08-01), Uchino et al.
patent: 4874979 (1989-10-01), Rapp
patent: 5225941 (1993-07-01), Saito et al.
patent: 5319257 (1994-06-01), McIntyre
patent: 5465021 (1995-11-01), Visscher et al.
patent: 5589723 (1996-12-0
Okamoto Yasuhiro
Yoshida Ryuichi
Budd Mark O.
Minolta Co. , Ltd.
Sidley & Austin
LandOfFree
Driving apparatus using transducer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Driving apparatus using transducer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driving apparatus using transducer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2574615