Electrical generator or motor structure – Non-dynamoelectric – Thermal or pyromagnetic
Reexamination Certificate
2000-04-11
2002-06-11
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Thermal or pyromagnetic
Reexamination Certificate
active
06404098
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a drive unit using a shape memory alloy, and particularly to a drive unit for moving a drive body to a specific operational position by using a shape memory alloy which exhibits superelasticity when energized.
A drive unit generally includes a shape memory alloy member made from a shape memory alloy containing titanium (Ti) and nickel (Ni) and a drive body connected to the shape memory alloy member, wherein the drive body is moved by energizing the shape memory alloy member.
FIGS. 7 and 8
show a related art drive unit “a” using a shape memory alloy.
The drive unit “a” is composed of a shape memory alloy spring “b” made from a shape memory alloy, a drive body “c”, and a bias spring “d”.
The shape memory alloy spring “b” is arranged such that one end is connected to the left side surface of the drive body “c” and the other end is fixed to a first fixing wall “e”. The bias spring “d” is arranged such that one end is connected to the right side surface of the drive body “c” and the other end is fixed to a second fixing wall “f”.
The shape memory alloy spring “b” is electrically connected to a power source (not shown). When energized by the power source, the shape memory alloy spring “b” exhibits superelasticity, and is thereby contracted to move the drive body “c” in the direction A from a stopping position shown in
FIG. 7
to an operational position shown in FIG.
8
.
When the energization of the shape memory alloy spring “b” is released, the drive body “c” is returned in the direction B from the operational position shown in
FIG. 8
to the stopping position shown in
FIG. 7
by the biasing force of the bias spring “d”.
The above-described related art drive unit “a”, however, has a problem. Since it is required to continue the energization of the shape memory alloy spring “b” for retaining the drive body “c” at the operational position, the power consumption becomes large. In particular, since the shape memory alloy containing Ti and Ni has a small inner resistance, the power consumption upon energization thereof becomes much larger. This brings a large obstacle to put the drive unit using the shape memory alloy into practical use.
The related art drive unit “a” also causes the following inconvenience: namely, in the case of retaining the drive body “c” at the operational position by continuing the energization of the shape memory alloy spring “b”, the drive body “c” tends to be oscillated, resulting in wobbling of the drive body “c” at the operational position.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a drive unit using a shape memory alloy, which is capable of reducing the power consumption while overcoming the above mentioned problems.
To achieve the above object, according to the present invention, there is provided a drive unit using a shape memory alloy, including: a shape memory alloy member made from a shape memory alloy, the shape memory alloy member exhibiting superelasticity when being energized; a drive body connected to the shape memory alloy member, the drive body being moved from a stopping position to a specific operational position when the shape memory alloy member is energized; and a locking mechanism for retaining the drive body at the specific operational position.
With this configuration, since it is not required to continue the energization of the shape memory alloy member for retaining the drive body at the specific operational position, it is possible to significantly reduce the power consumption.
The locking mechanism may be provided with a locking portion, and the drive body may be integrally provided with a portion to be locked with the locking portion. With this configuration, it is possible to reduce the number of parts and to certainly retain the drive body at the specific operational position.
The locking mechanism may be additionally provided with a locking-releasing mechanism for releasing the retention of the drive body at the specific operational position. With this configuration, it is not required to provide a locking-releasing mechanism separately from the locking mechanism. Accordingly, it is possible to reduce the number of parts and simplify the mechanism, and hence to miniaturize the drive unit using a shape memory alloy and reduce the production cost of the drive unit.
The locking-releasing mechanism may be provided with an extensible/contractible member which is made from a shape memory alloy and exhibits superelasticity when being electrified, whereby the retention of the drive body at the specific operational position is released by energizing the extensible/contractible member. With this configuration, it is possible to easily control the locking-releasing mechanism and certainly release the locking state of the drive body, and hence to ensure the desirable operational state of the drive unit.
The drive unit may further include a bias spring, connected to the drive body, for retaining the drive unit at the stopping position. With this configuration, it is possible to certainly retain the drive body at the stopping position and hence to optimize the operation of the drive unit.
REFERENCES:
patent: 4887430 (1989-12-01), Kroll
patent: 4979672 (1990-12-01), Abujudom
patent: 5070697 (1991-12-01), Van Zeggeren
patent: 5543678 (1996-08-01), Hoiberg
patent: 5637984 (1997-06-01), Chu
patent: 6285286 (2001-09-01), Tyren et al.
patent: 0919717 (1999-02-01), None
patent: 2172931 (1986-01-01), None
Kataoka Yasuhiro
Kayama Shun
Dougherty Thomas M.
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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