Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-09-13
2004-12-28
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S300000, C310S311000
Reexamination Certificate
active
06836057
ABSTRACT:
This application is based upon application No. 2000-280288 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 a drive mechanism employing an electromechanical transducer. More specifically, the present invention relates to the drive mechanism employing the electromechanical transducer or vibrating member, suitable for actuating a moving body equipped in an apparatus such as a precise device and a high-technology info tool, and for adapting a microactuator for minute operation.
2. Description of the Related Arts
Conventionally, there have been proposed some drive mechanisms employing electromechanical transducers. For example, in a drive mechanism as shown in
FIG. 11
, a moving body
51
contacts frictionally with a drive rod
53
, which is movably supported by stationary plates
62
and
63
. One end of the piezoelectric element
58
is fixed to the stationary plate
64
, and its opposite end is fixed to one of the ends of the drive rod
53
. In the arrangement, the piezoelectric element
18
expands at a first velocity and contracts at a second velocity, different from the first velocity, when the piezoelectric element
18
is supplied with drive pluses, for example, having a saw-teeth-shaped waveform. Thereby the drive rod
53
moves and the moving body
51
is driven along the drive rod
53
(See, for example, Japanese Non-examined Patent Publication No. 7-274544).
However, the strength of the piezoelectric element is low. Therefore, it is necessary to protect the piezoelectric element
58
from the excessive force.
Specifically, it is necessary to complicate the construction of the drive mechanism, and to limit the drive condition such as the drive velocity and the load, in order to prevent the external force from causing bending moment, torsion torque, compressive force, and tensile force to the piezoelectric element.
Additionally, it is necessary that expanding and contracting direction of the piezoelectric element
58
is precisely coincident with moving direction of the drive rod
53
moves. Therefore, it is difficult to assemble the drive mechanism, due to close tolerance of positioning the piezoelectric element
58
and drive rod
53
.
Moreover, the method for fixing the piezoelectric element
58
must be chosen from methods, in which no excessive force is exerted on the piezoelectric element
58
. The drive mechanism must be assembled without exerting the excessive force on the piezoelectric element
58
. Thus, it is difficult to assemble the drive mechanism efficiently.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a drive mechanism employing an electromechanical transducer, on which no excessive force is exerted.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a drive mechanism, comprising: a stationary member; a drive member fixed to the stationary member; an electromechanical transducer fixed to the drive member; and a driven member which is driven by the drive member and which contacts frictionally with the drive member under a predetermined frictional force exerting therebetween, wherein the electromechanical transducer is supplied with drive pulses, so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, different from the first velocity, and so that the driven member moves along the drive member in a predetermined direction.
In the construction, the electromechanical transducer (for example, electrostatic actuator, piezoelectric transducer, electrostriction transducer, magnetostriction transducer, and so on) changes the electrical energy (for example, electric voltage, electric current, electric field, electric charge, static electricity, magnetic field) supplied thereto into the mechanical energy (for example, transformation or strain such as prolonging, compressing, expanding, contracting, bending, twisting).
In the construction, even though the principle of driving is not completely clear, the driven member can be driven relative to the drive member in a predetermined direction, by means of supplying appropriate drive pulses, for example, having a saw-teeth-shaped waveform. Such drive pulses causes the transformation of the electromechanical transducer, so that the drive member vibrates with mutually different velocities, even if the drive member is fixed to the stationary member. Namely, the vibration of the drive member includes one component at relatively slow velocity proceeding in one direction, and the other component at relatively fast velocity proceeding in opposite direction. We reason; that the one component of the vibration does not cause the relative sliding between the drive member and the driven member; that the other component of the vibration causes the relative sliding therebetween; and that by repeating such a cycle, the driven member can be driven relative to the drive member in a predetermined direction.
In the construction, the electromechanical transducer is fixed to (or restrained by) only the drive member, and thereby, no excessive force is exerted on the electromechanical transducer.
As an embodiment, expansion and contraction of the electromechanical transducer makes the drive member vibrate, so that a cycle of the vibration of the drive member causes one state in which the driven member slides along (or is slidable along) the drive member in a predetermined direction, resisting the frictional force exerting therebetween, and another state in which the driven member does not slide along (or is unslidable along, or remains stationary against) the drive member with the frictional force exerting therebetween.
As an embodiment, the drive member has a pair of ends, so that a portion near one of the ends of the drive member is fixed to the stationary member, and so that the electromechanical transducer is fixed to the other of the ends of the drive member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between one positions fixed to the stationary member and the other position fixed to the electromechanical transducer, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, the drive member has a pair of ends, so that a portion near one of the ends of the drive member is fixed to the stationary member, and so that the electromechanical transducer is fixed to the one of the ends of the drive member.
According to the embodiment, it is possible to increases the space around the driven member.
As an embodiment, another portion near the other of the ends of the drive member is supported by the stationary member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between one position fixed to the stationary member and the other position supported by the stationary member, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, another portion near the other of the ends of the drive member is fixed to the stationary member.
According to the embodiment, it is possible to prevent the drive member from moving, and to have a driving range of the driven member along the drive member between two positions fixed to the stationary member, without any stopper for preventing the driven member from moving beyond the driving range.
As an embodiment, the stationary member is fixed to a lens barrel, and wherein the driven member holds a lens.
As an embodiment, the drive member is fixed to the stationary member by one of caulking, press fitting, fusion bonding, adhesive bonding, screw fastening, and welding.
As an embodiment, the drive member is formed with elastic material.
In order to achieve the above object, according to another aspect of the present invention, there is provid
Cuevas Pedro J.
Dougherty Thomas M.
McDermott Will & Emery LLP
Minolta Co. , Ltd.
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