Electrical generator or motor structure – Dynamoelectric – Reciprocating
Reexamination Certificate
2000-02-29
2001-10-23
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Reciprocating
C123S472000, C251S129010, C335S215000
Reexamination Certificate
active
06307286
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a super magnetostrictive actuator formed by combining at least two super magnetostrictive materials which extend and shrink in the longitudinal direction thereof due to the action of the magnetic field generated by a magnetic field generation means.
2. Description of the Related Art
Of the magnetostrictive materials which generate distortion in the magnetic field, rare earth metal monocrystal such as Tb (terbium), Dy (dysprosium) or the like known as super magnetostrictive material generates enormous magnetostriction which is about several hundred times as that generated by general magnetostrictive material such as Ni, Co or the like. Since TbFe
2
or DyFe
2
which is a binary alloy of Tb and Fe or Dy and Fe is able to generate enormous magnetostriction in the room temperature, such a binary alloy is used as a source for driving an actuator. However, enormous magnetostriction generated by such super magnetostrictive materials only exceeds the displacement of about 0.1% at most. Thus, in order to secure a required output displacement while avoiding the enlargement of the size of the actuator, it is required to combine a plurality of super magnetostrictive materials so as to accumulate slight extension and shrinkage amounts of the respective super magnetostrictive materials thereby to output the accumulated displacement.
Such a super magnetostrictive actuator for securing a required output displacement by combining a plurality of super magnetostrictive materials in this manner is known as disclosed in Japanese Patent Unexamined Publication NO. Hei.4-168984.
However, the aforesaid conventional super magnetostrictive a actuator is arranged in a manner that a plurality of super magnetostrictive materials formed in a column shape are disposed along the inner periphery of a coil formed in a cylindrical shape, and the end portions of the adjacent super magnetostrictive materials are coupled to each other by a link which is supported at its center portion by a fulcrum. According to the actuator thus arranged, an amount of extension and shrinkage of each of the super magnetostrictive materials is transmitted to the adjacent super magnetostrictive material through the link mechanism thereby to generate a required output displacement between the super magnetostrictive materials positioned at both ends.
However, in the conventional actuator, since the plurality of super magnetostrictive materials are coupled by the link mechanism, the number of the parts such as the link member and the fulcrum thereof etc. increases and the number of assembling processes thereof also increases. As a result, the cost of the actuator increases, and further the actuator may be prevented from moving smoothly since the magnitude of friction and the degree of wobble at a movable portion and a sliding portion increase.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforesaid conventional circumstances, and an object of the present invention is to provide a super magnetostrictive actuator which can obtain sufficient output displacement and operate smoothly with a simple and small-sized configuration having small number of parts.
In order to attain the aforesaid object, according to the present invention, there is provided a super magnetostrictive actuator formed by combining at least first and second super magnetostrictive materials which expand and shrink in a longitudinal direction thereof due to action of magnetic field generated by magnetic field generating means. The second magnetostrictive material of tubular shape is disposed coaxially so as to surround outer side of the first magnetostrictive material along radial direction thereof, and a coupling member of tubular shape disposed coaxially between the first and second super magnetostrictive materials is coupled at its both end portions to one end portion of the first magnetostrictive material and one end portion of the second magnetostrictive material, respectively.
According to the aforesaid configuration, when the magnetic field generating means generates magnetic field, both the first and second super magnetostrictive materials extend and shrink in the axial direction and so the deviation at the one end portion of the first magnetostrictive material is transmitted to the one end portion of the second magnetostrictive material through the coupling member. Thus, the deviation corresponding to the sum of amounts of extension/shrinkage of the first and second super magnetostrictive materials can be generated between the other end portion of the first magnetostrictive material and the other end portion of the second magnetostrictive material. Further, since the coupling member of tubular shape is disposed coaxially so as to surround the outer side of the first magnetostrictive material along the radial direction thereof and the second magnetostrictive material of tubular shape is disposed coaxially so as to surround the outer side of the coupling member along the radial direction thereof, not only can the super magnetostrictive actuator be configured in a small size but also the extension/shrinkage of the first and second super magnetostrictive materials can be effectively transmitted without causing offset load of the first and second super magnetostrictive materials. Furthermore, since the coupling member does not have a fulcrum nor a sliding portion and is merely coupled at its both end portions to the first and second super magnetostrictive materials, respectively, the number of the parts can be reduced thereby to realize a simple configuration and so the actuator is advantageous in economical efficiency, endurance and assembling efficiency.
Further, the magnetic field generating means may be formed by a coil disposed coaxially so as to surround the outer periphery of the second magnetostrictive material.
According to the aforesaid configuration, the output deviation of the super magnetostrictive actuator can be easily controlled by merely changing the pulse width or the magnitude of the current supplied to the coil. Further, since all the first and second super magnetostrictive materials, the coupling member and the coil are disposed coaxially, the super magnetostrictive actuator can be further configured in a smaller size.
REFERENCES:
patent: 4804314 (1989-02-01), Cusack
patent: 5332942 (1994-07-01), Rennex
patent: 5361053 (1994-11-01), Hosokawa et al.
patent: 5868375 (1999-02-01), Reinicke et al.
patent: 4-168984 (1992-06-01), None
Goto Hiroyuki
Otaka Akifumi
Yamazaki Hideharu
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Mullins Burton S.
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