Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-02-12
2001-08-21
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06278221
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor having a force applying means for applying a force to a vibrating member and moving member, and more particularly to an ultrasonic motor having a force applying means for applying a force to be adjusted before or after assembling the vibrating member, moving member and so on, and to an electronic apparatus with such a ultrasonic motor.
In the field of micro-motors, attention has recently been drawn to ultrasonic motors that utilize a piezoelectric effect provided by a piezoelectric element.
There is known, as one example of such an ultrasonic motor, a type that is provided with a support plate, a center shaft fixed to the support plate, a vibrating member fixed on the center shaft, a piezoelectric element joined to an underside of the vibrating member, a moving member placed in abutment against a projection provided on the vibrating member, and a force applying means placed in pressure contact with the moving member.
According to this art, the piezoelectric element is vibrated so that the vibration of the piezoelectric element causes the vibrating member to elastically vibrate. Through this elastic vibration, the projection of the vibrating member is brought into contact with the moving member, with a certain periodicity. Meanwhile, the force applying means applies a force to the moving member and the projection on the vibrating member to generate a frictional force between the moving member and the vibrating member, thus driving the moving member through the frictional force.
Here, it is known that the force applying means includes, in kind, a leaf spring
101
as shown in
FIG. 11A
or a dish-shaped spring
102
as shown in
FIG. 11B
, and one formed by a spacer for adjusting the force of the dish-shaped spring (see Japanese Patent Laying-open No H2-287281 and Japanese Patent Laying-open No S63-305770).
In the case of the leaf spring
101
, however, there is encountered a variation in force due to a shape of the leaf spring, variation in thickness thereof, variation in thickness of parts such as the vibrating member and the moving member, and variation caused by assembling these parts. Such variation in force in turn causes change in the frictional force between the vibrating member and the moving member and also the drive force to the moving member, thus posing a problem of causing variation in individual characteristics of the ultrasonic motor.
On the other hand, where using the dish-shaped spring
102
and the spacer, the force can be adjusted by adjusting the variation in such parts as the dish-shaped spring, vibrating member and moving member, through controlling a spacer thickness. Nevertheless, the force adjustment still requires troublesome operations, such as combining parts due to thickness selection before assembling and disassembling for motor characteristic inspection after assembling, e.g., changing the number of spacers. Furthermore, the adjustment with spacers, even if there is slight difference in thickness, induces greater variation in force applied. Due to this, it is impossible to accurately adjust the force, resulting in such problems as increase in size and decrease in efficiency of the apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide, in view of the above-stated problems, a small, efficient and stable ultrasonic motor in which prevention is made for variation in force before and after assembling its vibrating member, moving member and so on and adjustment of force is possible without requiring troublesome operations after the assembling, and to provide an electronic apparatus with such an ultrasonic motor.
FIG. 1
is a block diagram showing a concept of the present invention.
According to the present invention, an ultrasonic motor, has a force applying means
3
for applying a force to a vibrating member
1
to be vibrated as well as to a moving member
2
placed in abutment against the vibrating member
1
to cause a frictional force between them so that the moving member
2
is driven by the frictional force, wherein the force applying means
3
comprises: a main force applying means
3
a
for mainly applying a force; and a force adjusting means
3
b
for adjusting the force applied by the main force applying means
3
a.
In the above means, the force applying means
3
includes any of a scheme employing an elastic member, a scheme applying a force by a weight member, and further a scheme applying a force by attraction and repelling due to a magnet or the like. Also, the elastic member includes a spring and rubber, and further the spring includes a leaf spring, a spring with radial arms, a coiled spring, and the like.
FIG. 2
is a diagram equivalently representing a principle of the present invention.
The force applying means
3
is replaced by a structure having, in parallel connection, the main force applying means
3
a
formed by a spring with a greater elastic constant of K1 and the force adjusting means
3
b
formed by three springs each having a smaller elastic constant of K2,
Under a certain constant amount of deflection, the three springs of the force adjusting means
3
b
are connected or cut away to select a total elastic constant from among K1+3K2, K1+2K2, K1+K2 and K1, thereby adjusting the force.
According to the present invention, the force adjusting means
3
b
allows the force of the main force applying means
3
a
to be adjusted not only before assembling but also after the assembling. This accordingly prevents variation in the force due to variation in dimension of the vibrating member
1
, the moving member
2
and the force applying means
3
. Also, the vibrating member
1
, the moving member
2
and the force applying means
3
become easy to control on dimensional accuracy.
Also, after assembling, the force is adjusted without requiring a disassembly work. Accordingly, an adjustment of the force after assembling becomes easy.
Also, after assembling, the force is adjusted with accuracy by connecting or cut away the force adjusting means
3
b
. This accordingly realizes a motor that is small in size, high in efficiency and stable.
The force applying means may be a leaf spring, and the force adjusting means having slits and strip portions between the slits formed in the leaf spring.
According to this structure, the force can adjusted by the slits before assembling, and after the assembling the strip portions between the slits are cut away or connected, thus conducting an adjustment with accuracy.
The force applying means may have radially extending arms, the main force applying means being main force applying arm portions which are among the arms and have a predetermined width, and the force adjusting means being force adjusting portion adjusting portions which are among the arms and narrower in width than main force applying arms.
According to this structure, the force of the main force applying arms can be adjusted by the force adjusting arms before assembling, and after the assembling part of the force adjusting arms is cut away or bent, thereby conducting an accurate adjustment of the force.
The force adjusting means may be worked so as to adjust the force after assembling the vibrating member, the moving member and the force applying means.
Here, the working is due to a method of cutting, bending, fusion or the like.
This structure allows the force adjusting means to be worked after assembling the vibrating member and the like, enabling accurate adjustment of the force.
The force applying means and the moving member may be formed in one body.
This structure makes it unnecessary to use a member for providing the force applying means due to making the force applying means and the moving member in one body. This accordingly simplifies the apparatus structure.
An electronic apparatus can be provided with the ultrasonic motor.
Here, the electronic apparatus includes an electronic timepiece, measuring instrument, camera, printer, printing machine, machine tool, robot, and movable device.
This struct
Iino Akihiro
Kasuga Masao
Suzuki Makoto
Adams & Wilks
Dougherty Thomas M.
Seiko Instruments Inc.
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