Electrical generator or motor structure – Dynamoelectric – Reciprocating
Reexamination Certificate
2001-03-22
2004-04-13
Ponomarenko, Nicholas (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Reciprocating
C318S118000
Reexamination Certificate
active
06720684
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to magnetostrictive actuators, and particularly to magnetostrictive fuel injectors and electronic valve timing actuators for internal combustion engines. More particularly, this invention relates to an apparatus and method of using magnetic flux as a feedback variable to control the level of magnetostriction in a magnetostrictive actuator.
BACKGROUND OF THE INVENTION
It is believed that magnetostrictive actuators typically comprise a magnetostrictive member positioned within a solenoid coil, and a prestress mechanism for loading the magnetostrictive member to the nominal prestress value required to produce maximum magnetostriction. In the case of Terfenol-D, for example, it is believed that the magnetostrictive member may be prestressed to a value of about 7.6 MPa to maximize magnetostriction. However, it is believed that prestress may or may not be necessary, depending on the particular application and type of magnetostrictive material. It is believed that the solenoid coil generates the magnetizing force necessary to cause the desired magnetostriction in the magnetostrictive member.
The term “magnetostriction,” as it is used in this disclosure, means magnetic contraction, but it is generally understood to encompass the following similar effects associated with ferromagnetic materials: the Guillemin Effect, which is believed to be the tendency of a bent ferromagnetic rod to straighten in a longitudinal magnetic field; the Wiedemann Effect, which is believed to be is the twisting of a rod carrying an electric current when placed in a magnetic field; the Joule Effect, which is believed to be a gradual increasing of length of a ferromagnetic rod when subjected to a gradual increasing longitudinal magnetic field; and the Villari Effect, which is believed to be a change of magnetic induction in the presence of a longitudinal magnetic field (i.e., inverse Joule Effect). It is believed that the Villari Effect is the magnetostriction effect of greatest importance in actuator design. It is believed that typical magnetostrictive actuators utilize the Joule Effect for generating displacement and force.
It is believed that dimensional changes that occur when a ferromagnetic material is placed in a magnetic field are often considered undesirable because of the need for dimensional stability in precision electromagnetic devices. Therefore, it is believed that manufacturers of ferromagnetic alloys often formulate their alloys to exhibit very low magnetostriction effects. It is believed that ferromagnetic materials exhibit magnetic characteristics because of their ability to align magnetic domains. It is further believed that strongly magnetostrictive materials characteristically have domains that are longer in the direction of their polarization and narrower in a direction perpendicular to their polarization, thus allowing the domains to change the major dimensions of the ferromagnetic material when the domains rotate.
Alloys of Terbium (Tb), Dysprosium (Dy), and Iron (Fe) to form Tb
x
Dy
1−x
Fe
2
are believed to result in a magnetostrictive material in which useful strains may be attained. For example, the magnetostrictive alloy Terfenol-D (Tb
0.32
Dy
0.68
Fe
1.92
), is believed to be capable of approximately 10 &mgr;m displacements for every 1 cm of length exposed to an approximately 500 Oersted magnetizing field. The general equation for magnetizing force, H, in Ampere-Turns per meter (1 Oersted=79.6 AT/m) is:
H=IN/L
where I=Amperes of current; N=number of turns; and L=path length.
It is believed that Terfenol-D is often referred to as a “smart material” because of its ability to respond to its environment and exhibit giant magnetostrictive properties.
While the present disclosure is described primarily with reference to Terfenol-D as the magnetostrictive material, it will be appreciated by those skilled in the art that other alloys having similar magnetostrictive properties may be substituted and are included within the scope of the present disclosure.
SUMMARY OF THE INVENTION
The present invention provides a method of controlling a magnetostrictive actuator. The methol comprises energizing a coil with a current to generate magnetic flux within the coil; measuring the amount of magnetic flux generated in the coil; and applying the amount of magnetic flux generated in the coil as a feedback variable to selectively control the amount of magnetizing force applied to a magnetostrictive member located within the coil.
The present invention also provides a method of controlling a magnetostrictive actuator. The method comprises generating a magnetizing force acting on a magnetostrictive member located within a coil; measuring flux in the magnetostrictive member; and controlling the magnetizing force in response to the measuring flux.
The present invention further provides a magnetostrictive actuator. The actuator comprises a coil; a driver electrically coupled to the coil, the driver supplying current to the coil in an operating state; a magnetostrictive element magnetically coupled to the coil in the operating state; and a sensor magnetically coupled to the magnetostrictive element and electrically coupled to the driver, the sensor detecting magnetic flux in the magnetostrictive element and outputting to the driver a signal adjusting the current supplied to the coil.
REFERENCES:
patent: 3654540 (1972-04-01), Honig et al.
patent: 3857081 (1974-12-01), Gebelein, Jr.
patent: 4584980 (1986-04-01), Weiger et al.
patent: 4585978 (1986-04-01), Hasselmark et al.
patent: 4656400 (1987-04-01), Pailthorp et al.
patent: 4659969 (1987-04-01), Stupak, Jr.
patent: 5249117 (1993-09-01), Greenough et al.
patent: 5280773 (1994-01-01), Henkel
patent: 5479902 (1996-01-01), Wirbeleit et al.
patent: 5698911 (1997-12-01), Dunfield et al.
patent: 5713326 (1998-02-01), Huber
patent: 5819710 (1998-10-01), Huber
patent: 5915361 (1999-06-01), Heinz et al.
patent: 5991143 (1999-11-01), Wright et al.
patent: 6028382 (2000-02-01), Blalock et al.
patent: 6152372 (2000-11-01), Colley et al.
patent: 6176207 (2001-01-01), Wright et al.
patent: 6181036 (2001-01-01), Kazama et al.
patent: 6208497 (2001-03-01), Seale et al.
patent: 6288536 (2001-09-01), Mandl et al.
patent: 0 443 873 (1991-08-01), None
patent: 04004776 (1992-01-01), None
patent: 85/02445 (1985-06-01), None
English translation of Japanese reference H4-4776, published Jan. 1992, title “Magnetostrictive Element Driver”, inventor Kaysuya Uemura et al.*
PCT International Search Report; PC/US01/09077; Mar. 1, 2002.
“Self-Sensing Magnetostrictive Actuator for Adaptive Optics”, Jones L.D. et al., Journal of Guidance, Control, and Dynamics, vol. 19, No. 3, 1996, pp. 713-715, month unknown.
“Testing of a Magneto-Strictive Actuator for Adaptive Optics”, Bigelow B.C. et al., Optical Telescopes of Today and Tomorrow, Landskrona/HVEN, Sweden, May 29-Jun. 2, 1996, vol. 2871, pp. 910-919.
Jones Judson H.
Ponomarenko Nicholas
Siemens Automotive Corporation
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