Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-12-20
2004-05-18
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S323010, C310S323120, C310S325000
Reexamination Certificate
active
06737787
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor and a stator for an ultrasonic motor.
As shown in
FIG. 4
, a typical progressive wave type (or bolted Langevin type) ultrasonic motor includes a stator
51
and a rotor
52
. The stator
51
includes first and second blocks
53
,
54
, which are made of metal, first and second piezoelectric elements
55
,
56
, first to third electrode plates
57
to
59
, and a tightening member, which is a bolt
60
. The first and second blocks
53
,
54
, the first and second piezoelectric elements
55
,
56
, and the first to third electrode plates
57
to
59
are piled in layer to form a substantially columnar shape. The first and second blocks
53
,
54
are tightened by the bolt
60
, which is inserted through the first and second blocks
53
,
54
in the axial direction. This couples the first and second blocks
53
,
54
, the first and second piezoelectric elements
55
,
56
, and the first to third electrode plates
57
to
59
.
A slit, which is not shown, is formed at the outer circumference of the lower portion of the stator
51
, or the outer circumference of the second block
54
. The slit generates torsional vibration based on the axial vibration.
The rotor
52
is substantially cylindrical and is rotatably pressed against the upper surface of the stator
51
, or the upper surface of the block
53
, by a pressing mechanism, which is not shown.
When high-frequency voltage is applied to the first to third electrode plates
57
to
59
, the first and second piezoelectric elements
55
,
56
generate axial vibration. Then, the torsional vibration is generated at the slit of the second block
54
. The axial vibration of the stator
51
causes levitation force, and the torsional vibration causes driving force. The levitation force and the driving force cause the rotor
52
to rotate.
The first and second blocks
53
,
54
are assembled by tightening the male screw of the bolt
60
to the female screws of the first and second blocks
53
,
54
. This determines the positions of the first and second blocks
53
,
54
in the radial direction. Since the positions of the first and second blocks
53
,
54
and the bolt
60
are determined only by the male and female screws, the first and second blocks
53
,
54
could be misaligned. Therefore, manufacturing deviations are caused per stator
51
, which causes variations in the rotational characteristics (such as frequency-rotational speed characteristic, voltage-torque characteristic, and the like) per product. Therefore, the rotor
52
cannot be used for purposes in which a high-accuracy rotational control is required (such as for rotating a drum in a copying machine). This limits the field of application of the ultrasonic motor.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide an ultrasonic motor that has a simple structure and reduces misalignment of metal blocks and a tightening member, and a stator for the ultrasonic motor.
To achieve the above objective, the present invention provides an ultrasonic motor, which includes a stator and a rotor. The stator includes a pair of metal blocks, a piezoelectric element, a tightening member, and a positioning member. The piezoelectric element is located between the metal blocks. When drive voltage having a predetermined frequency is applied to the piezoelectric element, the piezoelectric element vibrates the stator. The tightening member is inserted through the metal blocks and the piezoelectric element to tighten the metal blocks and the piezoelectric element in the axial direction. The positioning member determines the radial position of the metal blocks. The rotor is press fit to the stator and rotates in accordance with the vibration of the stator.
The present invention also provides a stator located in an ultrasonic motor, which includes a pair of metal blocks, a piezoelectric element, a tightening member, and a positioning member. The piezoelectric element is located between the metal blocks. When drive voltage having a predetermined frequency is applied to the piezoelectric element, the piezoelectric element vibrates the stator. The tightening member is inserted through the metal blocks and the piezoelectric element to axially tighten the metal blocks and the piezoelectric element. The positioning member determines the position of the metal blocks in the radial direction.
REFERENCES:
patent: 4038570 (1977-07-01), Durley, III
patent: 4193009 (1980-03-01), Durley, III
patent: 5410204 (1995-04-01), Imabayashi et al.
patent: 6166477 (2000-12-01), Komoda et al.
patent: 6380660 (2002-04-01), Maeno et al.
patent: 6404104 (2002-06-01), Maeno et al.
patent: 8-308268 (1996-11-01), None
patent: 10-337051 (1998-12-01), None
patent: 2002-112561 (2002-04-01), None
patent: 2002-199754 (2002-07-01), None
patent: 2002-199755 (2002-07-01), None
patent: 2003-111452 (2003-04-01), None
Kato Yukiyasu
Komoda Masahiko
ASMO Co. Ltd.
Dougherty Thomas M.
Sheridan Ross PC
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