Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-03-10
2002-05-21
Sircus, Brian (Department: 2839)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000
Reexamination Certificate
active
06392328
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration motor including a vibration element in which a plurality of different vibrations are combined to generate elliptical vibratory motion. More specifically, the present invention is related to a vibration motor, including a base, a relative moving member, and a vibration absorbing member interposed between the base member and the relative moving member to prevent both the generation of noise and the reduction of driving efficiency by absorbing the vibration of the relative moving member, thereby eliminating the vibration of the base.
2. Description of the Related Art
Vibration motors which use so-called degenerate modes having different form, causing the simultaneous generation of two different vibrations, are disclosed, for example, in the
Fifth Dynamic Symposium Relating to Electromagnetic Force, Collected Papers
, Tomikawa, page 393.
FIG. 11
is a perspective view of a vibration motor
1
having a vibration element
2
disclosed by the Tomikawa reference. Moreover,
FIGS. 12A-12B
are illustrative diagrams of the vibration element
2
, wherein
FIG. 12A
is a top view,
FIG. 12B
is a side view, and
FIG. 12C
is a diagram showing examples of waveforms representing two different vibrations L
1
, B
4
generated by the vibration element
2
.
As shown in
FIGS. 11
,
12
A and
12
B, the vibration element
2
includes an elastic member
3
and an electromechanical conversion element
4
(referred to hereinbelow, where appropriate, as a “piezoelectric member”) which converts electrical energy into mechanical energy.
The respective dimensions of the vibration element
2
are set such that the natural frequencies of the first order longitudinal vibration L
1
and the fourth order torsional vibration B
4
about coincide. A piezoelectric member
4
having a plurality of electrodes
5
a
,
5
b
,
5
g
,
5
p
is affixed to one flat surface of the elastic member
3
. Moreover, two projecting driving force output members
3
a
,
3
b
are formed on a flat side of the elastic member
3
, opposite to the side to which the plurality of electrodes
5
a
,
5
b
,
5
g
,
5
p
are affixed.
As shown in
FIGS. 12B and 12C
, the driving force output members
3
a
,
3
b
are arranged with respect to the length direction of the vibration element
2
in positions which coincide with the outside antinode positions
11
,
14
among the four (4) antinode positions
11
,
12
,
13
and
14
of the bending vibration B
4
which is generated by the vibration element
2
.
The electrodes
5
a
,
5
b
are respectively excited by high frequency drive voltages V
A
, V
B
having phase mutually displaced by about &pgr;/2. As shown in
FIG. 12C
, upon exciting the electrodes
5
a
,
5
b
, there simultaneously arise in the elastic member
3
a first order longitudinal vibration L
1
and a fourth order bending vibration B
4
which vibrates in the thickness direction of the vibration element
2
. The combined the longitudinal vibration L
1
and the bending vibration B
4
generated in the elastic member
3
cause the respective bottom surfaces of the driving force output members
3
a
,
3
b
to vibrate in a manner which displaces them circumferentially (referred to herein as elliptical motion). The vibration element
2
is brought into pressure contact with a relative moving member
6
such that the elliptical motion of the driving force output members
3
a
,
3
b
moves the relative moving member in relative motion.
In the abovedescribed manner, the vibration element
2
generates a rectilinear relative movement, in the direction of the double arrow in
FIG. 11
, between the relative moving member
6
and the driving force output members
3
a
,
3
b
with which the relative moving member
6
is in pressure contact. Furthermore, in the vibration element
2
using degenerate modes having different form, the longitudinal vibration L
1
generated in the vibration element
2
is used as a propulsion force in the driving direction. Moreover, the bending vibration B
4
confers a function which propagates the longitudinal vibration L
1
intermittently to the relative moving member
6
(referred to herein as a “clutch function”). The clutch function causes rectilinear relative movement to be generated in one direction between the vibration element
2
and the relative moving member
6
.
SUMMARY OF THE INVENTION
The present applicant has found that when the vibration motor
1
is driven, a base member
7
of the relative moving member
6
vibrates at its natural frequency, and generates noise. The generation of noise is a very serious problem, since silent operation is an important feature of vibration motors.
Moreover, because the relative moving member
6
also vibrates accompanying vibration arising in the base
7
, the state of contact between the relative moving member
6
and the driving force output members
3
a
,
3
b
of the vibration element
2
becomes poor. Because of the poor contact between the relative moving member
6
and driving force output members
3
a
,
3
b
, the clutch function is impeded, driving efficiency decreases, and driving performance becomes poor.
It is an object of the present invention to provide a vibration motor having a vibration element using degenerate modes having different form which overcomes the problems of the conventional vibration motor and eliminates both the generation of noise originating in vibration of the base member, and the decrease of driving efficiency when driving the vibration motor.
The present inventor obtained the following information with respect to the origin of the vibration of the base member
7
. Specifically, in the vibration element
2
using degenerate modes having different form, because of the clutch function, the relative moving member
6
is normally in a state in which it is struck by the driving force output members
3
a
,
3
b
of the vibration element
2
. When the relative moving member
6
is struck by the driving force output members
3
a
,
3
b
, vibration is generated in the relative moving member
6
accompanying the striking. The vibration accompanying the striking is transmitted from the relative moving member
6
to the base member
7
, causing the base member
7
, which generally has a low natural frequency, to vibrate at its own natural frequency.
The present invention is based on the new information that both the generation of noise and the reduction of driving efficiency can be prevented by interposing a vibration absorbing member, which can absorb the vibration of the relative moving member, between the base member and the relative moving member, to thereby eliminate the vibration of the base.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a vibration motor comprising a vibration element including a driving force output member, which is excited to produce a combination of plural different vibrations, and generates an elliptical vibration in the driving force output member; a relative moving member in pressure contact with the driving force output member, to move in relative motion with respect to the vibration element; a first base member; a pressure support member, fixed between the vibration element and the first base member, to place the vibration element in pressure contact with the relative moving member; a second base member to support the relative moving member; and a vibration absorbing member to absorb vibration produced by the elliptical vibration generated by the vibration element in at least one of the relative moving member and the pressure support member, the vibration absorbing member being disposed in at least one of between the first base member and the pressure support member, between the pressure support member and the vibration element, and between the relative moving member and the second base member.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a vibration motor comprisi
Nikon Corporation
Sircus Brian
Zarroli Michael C.
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