Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-05-21
2004-09-07
Budd, Mark (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06787971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the construction of a contact portion of a vibrating member or a moving member for use in a vibration wave driving device, and to a method of processing this contact portion.
2. Related Background Art
A vibration wave motor, which is a vibration wave driving device, has a vibrating member generating vibration serving as a drive source, and this vibrating member is composed of an elastic member and a piezoelectric element serving an electro-mechanical energy conversion element. A piezoelectric element has two drive phases that have a phase shift of, for example, 90 degrees. When drive signals (alternating signals) having a phase shift of 90 degrees are applied to these two drive phases, a vibration which is a traveling wave is generated wave is generated on the surface of the elastic member. When a rotor is brought into press contact with this elastic member, the rotor is driven by the traveling wave generated on the surface of the elastic member.
Conventional well-known vibration wave motors of the type in which a rotor is rotated are annular, disc-like, or bar-like configurations. In the following, the construction of a bar-like vibration wave motor will be described.
FIG. 12
is a sectional view of an example of a conventional bar-like vibration wave motor. A vibrating member
1
generating vibration is constructed of elastic members
9
and
10
formed of metal or the like; a frictional ring
9
b
attached to the forward end surface of the elastic member
9
by adhesion, brazing or the like and formed, for example, of alumina ceramics; and a laminated piezoelectric element
11
held between the elastic members
9
and
10
and serving as a layered electromechanical energy conversion element.
After attaching the frictional ring
9
b
to the elastic member
9
, the surface of the frictional ring
9
b
which is on the opposite side of the attachment surface, that is, the frictional surface, is polished to enhance its flatness and to smoothen its surface.
At the center of the elastic member
9
, the piezoelectric element
11
, and the elastic member
10
, there is formed a through-hole, into which a support bar
5
constituting a framework member of the motor is inserted. One end portion of the support bar
5
protrudes beyond the elastic member
10
, and a nut
6
is engaged with a screw portion
5
b
formed on the protruding portion. The support bar
5
has a large diameter portion
5
a
in contact with a step formed on the inner side of the elastic member
9
. By fastening the nut
6
, the elastic member
9
, the laminated piezoelectric element
11
and the elastic member
10
, which are held between the large diameter portion
5
a
and the nut
6
, are pressed against each other and secured in position.
Reference numeral
2
indicates a rotor (moving member) arranged opposite the forward end surface of the elastic member
9
. It is composed of a cylindrical main body
21
and a contact spring
22
fitted onto the outer periphery of the main body
21
, and both components are joined together by adhesion, welding or the like. The rotor
2
is engaged with an output gear
4
rotating integrally with the rotor
2
; this gear
4
slides on a motor mounting flange
7
through the intermediation of lubricating oil. A screw portion
5
c
at the other end of the support bar
5
is fixed to the flange
7
, and the vibrating member
1
is supported by fixing the flange
7
to a bottom board (not shown) by means of a screw. On the inner wall of the through-hole at the center of the main body
21
of the rotor
2
, there is formed a step constituting a spring seat portion
21
a
, and a pressure spring
8
is arranged between the spring seat portion
21
a
and the output gear
4
, the contact spring
22
of the rotor
2
being brought into press contact with the frictional ring
9
b
of the vibrating member
1
.
The driving principle of the vibration wave motor of
FIG. 12
is as follows. A detailed description of the laminated piezoelectric element
11
will be omitted. When a two-phase alternating voltage is applied to the laminated piezoelectric element
11
, an expansion and contraction movement is generated in the laminated piezoelectric element
11
, and primary bending natural vibrations in a direction parallel to the plane of
FIG. 12 and a
direction perpendicular to the plane of
FIG. 12
are generated in the vibrating member
1
. When the two vibrations are generated with a phase shift in time of 90 degrees, a rightward or a leftward circular motion is generated in the vibrating member
1
around the position of the support bar
5
in case that there is no vibration. The elastic member
9
has a groove
9
a
for enlarging the vibration displacement, and a swinging motion as indicated by the arrows of
FIG. 12
is generated at the forward end of the elastic member
9
. As seen from the contact surface (the upper surface of the frictional ring), this vibration corresponds to a 1-wave traveling wave. When the rotor
2
having the contact spring
22
is brought into pressure contact with the vibrating member
1
, the rotor
2
comes into contact with the upper surface of the frictional ring
9
b
with only one portion thereof in the vicinity of the antinode of the traveling wave shifted to the rotor side of the vibrating member
1
, and rotates in the direction opposite to the traveling direction of the traveling wave. The rotation output of the rotor
2
is extracted by the gear
4
engaged with the main body
21
of the rotor
2
and the flange
7
.
The natural mode of the vibrating member
1
is designed such that the vibration amplitude of the flange
7
is very small, and the main body
21
of the rotor
2
is designed such that its inertial mass is large enough not to allow any vibration to be caused by the excitation of the vibrating member
1
. Further, the contact spring
22
of the rotor
2
is designed such that its natural frequency is sufficiently higher than the driving frequency of the vibrating member and that it follows the vibration.
Note that the contact spring
22
of the rotor
2
is formed through heat treatment of stainless steel to achieve an increase in hardness to thereby enhance wear resistance, and there is no fear that edge chipping will occur as in the case of a contact spring formed of anodized aluminium. The frictional ring
9
b
is harder than the contact spring
22
. Since it is mainly the contact spring
22
that is worn, the frictional ring
9
b
is hardly rutted.
Here, the contact spring
22
of the rotor
2
will be described with reference to the enlarged view of FIG.
13
.
The contact spring
22
is composed of a thin-walled spring portion
22
a
having elasticity mainly in the radial direction, a thin-walled spring portion
22
b
which is a flange portion connected to the spring portion
22
a
and having elasticity in the axial direction, and a forward end portion
22
c
connected to the spring portion
22
b
. As stated above, the end surface of the forward end portion
22
c
constituting the surface coming into contact with the frictional ring
9
b
is polished to enhance its flatness and to be smoothened after attaching the contact spring
22
to the main body
21
.
Note that when the contact spring
22
is formed by a press or the like, the end surface of the forward end portion
22
c
prior to the processing is not flat as shown in
FIG. 14
, and there is a fluctuation in an axial dimension H. Thus, it is necessary to flatten the end surface of the forward end portion
22
c
by grinding or rough-polishing and to attain a predetermined axial dimension before performing finish polishing.
In the case of grinding, it is possible to accurately attain the axial dimension H of the forward end portion
22
c
. However, large burr is generated at the end surface, which leads to a rather long finish polishing time. Further, in the case of rough-polishing, the end surface can be formed neatly. However, due to the small width of the end surface, the polishing is
Kimura Atsushi
Maruyama Yutaka
LandOfFree
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