Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-02-19
2001-06-26
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000
Reexamination Certificate
active
06252333
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a stage utilizing a piezoelectric actuator or ultrasonic motor movable on a two-dimensional plane and electronic equipment and a printer utilizing the stage.
Recently, an X-Y stage having single axis ables overlapped in the vertical direction at a crossing angle of 90° to each other is often used to measure and process two-dimensional objects.
It is common to employ a method in which the rotation of an electromagnetic motor is converted into a linear motion with a feed screw in each of X- and Y-directions or a method in which linear driving is performed with an electromagnetic linear motor in each of the X- and Y-directions (refer to JSPE-57-10, '91-10-1726).
In the case of the method in which motors and feed screws are combined, however, positioning accuracy is reduced by back-lash at the screw portions or thermal expansion of the screw portions. Further, the mechanism becomes complicated and large because the screw portions must be provided such that they cover the entire amount of desired feed.
In the case of an electromagnetic linear motor, positioning accuracy is limited by the relationship between the poles of the permanent magnet and the coil for generating a magnetic field. Specifically, the coil tends to stop in the vicinity of a pole of the permanent magnet and, as a result, it is difficult to stop the X-Y stage at an intended position. Further, the coil or permanent magnet must be provided such that it covers the entire amount of desired feed, which makes the mechanism complicated and large.
The above-described methods also have had a problem in that they are not usable in an environment where magnetization is avoided because components around the stage are magnetized by an electromagnetic force and circuits round the stage are susceptible to electromagnetic noises.
Meanwhile, ultrasonic motors utilizing a piezoelectric effect of a piezoelectric element are attracting attention in the field of micro-motors. Especially, ultrasonic motors utilizing an oscillator which undergoes stretching oscillation and bending oscillation (duel mode oscillator) are used in various applications because they cause a linear motion, a rotary motion and the like at an object with composite oscillation which is a synthesis of the two kinds of oscillation (see Japanese unexamined patent publication No. H7-184382).
SUMMARY OF THE INVENTION
It is an object to provide a stage utilizing an ultrasonic motor with which positioning accuracy can be improved, which has a simple and compact mechanism and which can be used in an environment where magnetization is avoided and electronic equipment and a printer utilizing the same.
Specifically, as set forth in claim
1
, means for solving the above-described problems is a stage including a first moving body which is movable in one direction and a second moving body which moves in one direction with said first moving body and which is movable in another direction different from said one direction, characterized in that it comprises:
a first piezoelectric actuator or ultrasonic motor which is put in contact with said first moving body for moving the moving body in said one direction and a second piezoelectric actuator or ultrasonic motor which is put in contact with said second moving body for moving the moving body in said other direction.
In the above-described solving means, the piezoelectric actuator or ultrasonic motor comprises any of a method wherein elliptical oscillation is obtained in a position between an antinode and a node of bending oscillatory wave, a method wherein a progressive wave in generated by a first bending oscillatory wave and a second bending oscillatory wave, a method wherein elliptical oscillation is obtained from a stretching oscillatory wave and a bending oscillatory wave and a method wherein elliptical oscillation is obtained from a stretching oscillatory wave and a torsional oscillatory wave.
Materials for a piezoelectric element used in the piezoelectric actuator or ultrasonic motor include barium titanate., lead titanate zirconate, lithium niobate and lithium tantalate.
Further, each moving body may be moved by a single or a plurality of piezoelectric actuator or ultrasonic motor. While the one direction and the other direction may be selected appropriately, the one direction and the other direction are preferably orthogonal to each other to move the second moving body efficiently.
According to the above, the first piezoelectric actuator or ultrasonic motor is put in contact with the first moving body for applying a frictional force in one direction to move the first moving body in the one direction, and the second moving body is also moved as the first moving body is moved.
The second piezoelectric actuator or ultrasonic motor is put in contact with the second moving body for applying a frictional force in another direction to move the second moving body in the other direction. The second moving body freely moves a plane comprising the one direction and the other direction.
That is, since each of the piezoelectric actuators or ultrasonic motors is put in contact with a moving body to apply a frictional force thereto directly, there is no need for providing a mechanism for transmitting a driving force between the moving body and an oscillator and, therefore, the configuration of the apparatus is made simple and compact. Further, there is neither back-lash nor errors associated with the provision of a mechanism for transmitting a driving force.
Since the piezoelectric actuators and ultrasonic motors are not stopped in any particular position by factors such as a magnetic force unlike electromagnetic motors, the positioning accuracy of the moving bodies is improved.
In addition, since no electromagnetic noise is generated, it may be used in an environment where magnetization is avoided.
As set forth in claim
2
, there is provided a stage utilizing a piezoelectric actuator or ultrasonic motor according to claim
1
, characterized in that it comprises a first urging mechanism for urging said first piezoelectric actuator or ultrasonic motor against said first moving body and a second urging mechanism for urging said second piezoelectric actuator or ultrasonic motor against said second moving body.
In the above-described means, the urging mechanism comprises urging means utilizing an elastic member. The elastic member comprises a coil spring, flat spring, a spring of other kind, rubber or the like.
According to the above, the first urging mechanism urges the first piezoelectric actuator or ultrasonic actuator against the first moving body to generate an adequate frictional force between the first piezoelectric:, actuator or ultrasonic motor and the first moving body, and the second urging mechanism urges the second piezoelectric actuator or ultrasonic motor against the second moving body to generate an adequate frictional force between the second piezoelectric actuator or ultrasonic motor and the second moving body. Therefore, the first moving body and second moving body move at an adequate speed.
As set forth in claim
3
, there is provided a stage utilizing an ultrasonic motor according to claim
1
, characterized in that at least either said first ultrasonic motor or said second ultrasonic motor comprises an elastic body and a piezoelectric element for generating a first bending oscillatory wave and a second bending oscillatory wave having a phase shifted from that of said bending oscillatory wave at the elastic body; elliptical oscillation is generated the elastic body by the first bending oscillatory wave and second bending oscillatory wave; and a frictional force is applied to the moving body based on the elliptical oscillation.
The above-described means may comprise any of an elastic body and the like provided only in the first piezoelectric actuator or ultrasonic motor, an elastic body and the like provided only in the second piezoelectric actuator or ultrasonic motor and elastic bodies and the like provided in the first piezoelectric actuator or ultra
Iino Akihiro
Kasuga Masao
Adams & Wilks
Dougherty Thomas M.
Seiko Instruments Inc.
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