EP0406692B1 - Fluide pouvant répondre à l'influence d'un champ magnétique - Google Patents

Fluide pouvant répondre à l'influence d'un champ magnétique Download PDF

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Publication number
EP0406692B1
EP0406692B1 EP90112257A EP90112257A EP0406692B1 EP 0406692 B1 EP0406692 B1 EP 0406692B1 EP 90112257 A EP90112257 A EP 90112257A EP 90112257 A EP90112257 A EP 90112257A EP 0406692 B1 EP0406692 B1 EP 0406692B1
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EP
European Patent Office
Prior art keywords
carbonyl iron
dispersant
fluid composition
composition
fluid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP90112257A
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German (de)
English (en)
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EP0406692A2 (fr
EP0406692A3 (fr
Inventor
Emil Meyer Shtarkman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Northrop Grumman Space and Mission Systems Corp
Original Assignee
TRW Inc
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Publication of EP0406692A3 publication Critical patent/EP0406692A3/fr
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Publication of EP0406692B1 publication Critical patent/EP0406692B1/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H01F1/447—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids

Definitions

  • the present invention relates to a rheological fluid which is responsive to a magnetic field.
  • Rheological fluids responsive to magnetic fields are known.
  • Rheological fluids responsive to electric fields are also known. Such fluids are used in clutches, shock absorbers, and other devices.
  • a characteristic of these rheological fluids is that, when they are exposed to the appropriate energy field, solid particles in the fluid move into alignment and the ability of the fluid to flow is substantially decreased.
  • Electric field responsive fluids and magnetic field responsive fluids include a vehicle, for instance a dielectric medium, such as mineral oil or silicone oil, and solid particles.
  • a dielectric medium such as mineral oil or silicone oil
  • solid particles are magnetizable.
  • Examples, of solid particles which have been heretofore proposed for use in a magnetic field responsive fluid are magnetite and carbonyl iron.
  • the fluid also may contain a surfactant to keep the solid particles in suspension in the vehicle.
  • US-A-4,604,229 discloses the combination of a hydrocarbon carrier with 4%-10% magnetite, 8%-12% electrically conductive carbon black, and a dispersing agent.
  • Powder magnetite Fe3O4
  • Fe3O4 is the fully oxidized magnetic oxide of iron, carbonyl iron, or iron-nickel.
  • US-A-3,006,656 discloses a magnetic particle shock absorber using a composition which can contain carbonyl iron, a vehicle such as oil, and graphite. Carbonyl iron and magnetite are described as equivalant materials in the composition. It is not indicated in the patent which carbonyl iron was used.
  • US-A-2,519,449 discloses the combination of carbonyl E and solid, powdered graphite in a 50/50 blend.
  • the continuous phase or dielectric medium in the composition is air.
  • the graphite functions as a lubricant.
  • US-A-2,661,596 discloses a magnetically-responsive fluid which comprises 100 parts of iron carbonyl powder, 10 parts dielectric oil, and 2 parts dispersant, such as ferrous oleate. The form of carbonyl iron used is not disclosed.
  • US-A-2,663,809 and US-A-2,886,151 disclose the use of carbonyl iron in a fluid coupling. The form of carbonyl iron used is not disclosed.
  • US-A-2,772,761 discloses an electromagnetic clutch using a magnetically-responsive fluid comprising an iron powder which is an 80/20 blend of plast-iron and carbonyl "E", and a dispersant comprising 39% graphite, 46% naptha, and 15% alkyl resin, by way of example.
  • the carbon fibers of the individual particles are intertwined forming a porous structure.
  • the particles are capable of incorporating and suspending other finely divided powders in fluids.
  • the fluid composition of the present invention comprises a vehicle and solid magnetizable particles suspended in the vehicle.
  • the fluid composition also contains a dispersant.
  • the magnetizable particles are insulated, reduced carbonyl iron particles.
  • the present invention also resides in the discovery of a novel dispersant for a magnetic field responsive fluid, which dispersant is fibrous carbon particles, each particle of which comprises intertwined carbon fibers having a length-to-diameter ratio in the range of about 10:1 to about 1,000:1.
  • the fibers Preferably, have a surface area of about 300 square meters per gram.
  • the fluid composition of the present invention comprises a vehicle, such as mineral oil, silicone oil, or CONOCO LVT oil; an insulated reduced carbonyl iron; and preferably a dispersant of intertwined carbon fiber particles.
  • Carbonyl iron is manufactured by the decomposition of iron pentacarbonyl Fe(CO)5. This process produces a spherical unreduced particle which has what is referred to as an onion-skin structure due to minute carbon deposits in alternating layers. The carbon content is about 1%. Reduction or de-carburization of the unreduced powder is carried out by exposing the powder to a hydrogen atmosphere, followed by compaction. This destroys the onion-skin structure and produces a composite of randomly arranged minute iron particles. The carbon content of the powder is about 0.075%.
  • the reduced powders have an insulation coating to prevent particle-to-particle contact.
  • the particles are physically soft and compressible. Their shape is spherical.
  • Reduced particles which are also insulated are marketed by GAF Corporation under the designations "GQ-4" and "GS-6".
  • GQ-4" Reduced particles which are also insulated
  • the following Table 1 gives physical and chemical properties for the insulated, reduced powders: The data of Table 1 can be found on page 4 of the GAF brochure mentioned above, bearing the identifying code IM-785. The disclosure of the GAF brochure is incorporated herein by reference.
  • the insulation coating can be any particle-coating agent capable of insulating the carbonyl iron particles and preventing interparticle eddy currents or dielectric leakage.
  • the insulation coating on the "GQ-4" and "GS-6" powders is a discontinuous layer of silicon oxide, primarily silicon dioxide. Silicon comprises about 6.9 atomic percent of the surface composition of the carbonyl iron particles. Silicon dioxide is very dielectric, and provides electrical resistivity.
  • the reduced powders have a more random arrangement of minute iron particles than the so-called "straight" powders, and that this results in a lower hysteresis effect than with the "straight" powders.
  • the insulation on the powders enhances the efficiency of the magnetic fluid in reducing parasitic eddy currents around the particles, which eddy currents could adversely affect the magnetic field strength in the fluid.
  • the moving parts of the clutch stir the composition effectively and no dispersant is required. This is particularly the case where permanent magnets are used, and thus the clutch is never demagnetized. In such an instance, settling of the iron particles presents no problems.
  • the composition of the present invention can employ any dispersant or surfactant conventionally employed with a fluid responsive to a magnetic field.
  • surfactants employed in the prior art are: dispersants, such as ferrous oleate or ferrous naphthenate; aluminum soaps such as aluminum tristearate or aluminum distearate; alkaline soaps, such as lithium stearate or sodium stearate, employed to impart thixotropic properties; surfactants such as fatty acids, e.g., oleic acids; sulfonates, e.g., petroleum sulfonate; phosphate esters, e.g., alcohol esters of ethoxylated phosphate esters; and combinations of the above.
  • a preferred dispersant material is fibrous carbon.
  • Fibrous carbon is a carbon particulate in which each carbon particle is composed of a large number of intertwined small carbon fibers.
  • One such fibrous carbon is "TRW Carbon", trademark, TRW corporation.
  • TRW Carbon is disclosed in the publication "Quest”, mentioned above. The disclosure of this publication is incorporated herein by reference.
  • the "TRW Carbon” is made in a catalytic carbon disproportion reaction in which a low heating value fuel gas or other source of carbon is used as the reaction feed.
  • the individual fibers in the fibrous carbon are from 0.05 to 0.5 microns in diameter and up to several thousand times as long as they are thick. A preferred average length to diameter ratio is in the range of about 10:1 to about 1,000:1.
  • Most of the fibers contain a single crystallite of a ferrous metal (such as iron, nickel, cobalt, or their alloys) or ferrous metal carbide.
  • the carbon fibers grow during the disproportion reaction from opposite faces of the single crystallites.
  • the crystallite usually represents 1 to 10 percent by weight of the material, but can be reduced to as low as 0.1 percent by acid leaching. Except for the crystallite, the fibers are almost pure carbon plus a small amount of hydrogen such as 0.5 to 1 percent.
  • the fibers may be either hollow or porous.
  • the intertwining and formation of small interstices in the carbon particles allows the fibrous carbon to incorporate the micron-sized carbonyl iron paticles and mechanically suspend the carbonyl iron particles dispersed in a fluid carrier.
  • the fibrous carbon particles have a large surface area of about 300 square meters per gram and a low bulk density of about 0.02 to about 0.7 grams per milliliter. Pore volume of the fibrous carbon particles typically is about 0.5 to about 0.9 milliliters per gram.
  • the fibrous carbon particles have fluid-like characteristics and flow like a liquid similar to graphite. When placed in a liquid vehicle, in a dispersing amount, they thicken or gell the vehicle preventing settling of the carbonyl iron particles. They form a thixotropic mixture with the vehicle which has good flow properties when exposed to shear. The viscosity of the thixotropic mixture is relatively independent of temperature.
  • the vehicle of the composition of the present invention can be any vehicle conventionally employed in a fluid responsive to a magnetic field.
  • suitable vehicles are set forth in the prior art referenced above.
  • the vehicle employed is an oil having a viscosity at about 37,78°C (100°F) between one and 1,000 centipoises.
  • the proportions of ingredients employed in the composition of the present invention can vary over wide ranges.
  • the dispersant is employed in an amount effective to disperse the carbonyl iron particles and to maintain such particles in suspension in the vehicle.
  • the amount of vehicle used is that amount necessary for the vehicle to function as the continuous phase of the composition. Air pockets in the composition should be avoided.
  • the remainder of the composition is essentially the carbonyl iron powder.
  • the carbonyl iron to dispersant weight ratio is about 90:10 to about 99.5:0.5.
  • the weight of the vehicle is about 15% to about 50% of the combined weight of the carbonyl iron and dispersant.
  • composition of the present invention has thixotropic properties and is mechanically stable in the sense that the compositions remain homogeneous for prolonged periods of time.
  • compositions consisting essentially of insulated, reduced carbonyl iron and vehicle
  • the vehicle is employed in an amount effective so that it is the continuous phase in the composition.
  • the specific amount used is dependent upon the properties of the vehicle, such as viscosity.
  • a preferred weight ratio of vehicle to carbonyl iron is in the range of about 15%-55% vehicle to about 85%-45% carbonyl iron.
  • test apparatus was constructed to determine the coupling load characteristics of the composition under various conditions.
  • the test apparatus is similar in construction to the shock absorber disclosed in co-pending Application Serial No. 339,126, filed April 14, 1989, assigned to the assignee of the present application.
  • the test apparatus is illustrated in the drawings of this application.
  • the test apparatus 12 comprises a non-magnetic aluminum housing 14.
  • the housing 14 comprises first and second housing sections 16 and 18 (Fig. 2) which are fastened together by bolts 20.
  • the housing sections 16, 18 define a fluid chamber 22 (Fig. 2) in the right end portion 24, as viewed in the drawings, of the housing.
  • a shaft 26 extends through the left end portion 28, as viewed in the drawings, of the housing 14.
  • the shaft 26 has shaft end sections 30 and 32 (Fig. 2) and a shaft center section 34.
  • the shaft 26 rotates in bearing assemblies 36 and 38. Seals 40, 42 prevent fluid leakage along the shaft 26.
  • the center section 34 of the shaft 26 has a square configuration.
  • a rotor blade 44 is fixed to the center section 34 so as to rotate with the shaft.
  • the rotor blade 44 has a configuration as shown in Fig. 3. It extends radially from the shaft center section 34 into the fluid chamber 22.
  • the right-end portion 24 of the housing 14 has an opening 45 in which holder 46 for an electromagnet 54 is located and an opening 47 in which a holder 48 is located for an electromagnet 56.
  • the holders 46, 48 have chambers 50, 52, respectively, in which the electromagnets 54, 56 are located.
  • the holders 46, 48 are secured to the housing sections 16 and 18 by means of brackets 58, 60, respectively. Screws 62, 64 hold the coil holders 46, 48 to the brackets 58, 60, respectively. Screws 66 (Fig. 1) hold the brackets 58, 60 to the housing sections 16, 18.
  • the electromagnets 54, 56 can be chemically bonded to the holders 46, 48 or alternatively fastened to the holders by screws not shown.
  • the non-magnetic material of the housing 12 and holders 46, 48 minimizes leakage of magnetic flux from the electromagnets 54, 56.
  • Figs. 4, 5 and 6 show details of the electromagnets 54, 56.
  • Each electromagnet 54, 56 comprises a soft iron core 70 around which an electrical coil 72 is wound.
  • the electrical coil 72 is covered with an encapsulating material such as an epoxy.
  • Each of the electromagnets 54, 56 has a pair of wire ends 74.
  • An outer soft iron pole 76 extends around the coil 72.
  • the electromagnets 54, 56 are mounted so that the poles of the electromagnets 54 face the poles of the electromagnet 56.
  • the rotor blade 44, and the fluid chamber 22, are positioned between the electromagnets 54, 56.
  • the spacing between one electromagnet and the blade is about 0.25 millimeters.
  • the blade thickness is about two millimeters.
  • the center core 70 of each electromagnet has a diameter of 38,10 mm (1.50 inches).
  • the outside diameter of each electromagnet is 76,20 mm (three inches).
  • the outer pole 76 has a radial thickness of 4,76 mm (0.1875 inches).
  • Each electromagnet coil 72 has 894 wire turns.
  • each electromagnet When the coils 54, 56 are energized, each electromagnet generates its own magnetic field. Lines of magnetic flux are established between the two electromagnets. The lines of magnetic flux pass through the fluid in the fluid chamber 22 and through the rotor blade 44. These lines of magnetic flux act on the fluid in the fluid chamber 22 to vary the resistance to movement of the rotor blade 44 in the fluid.
  • the shaft 26 was connected by means of arms 78 (Fig. 2) to a torque motor (not shown).
  • the torque motor was associated with a means for measuring torque. Different currents were applied to the electromagnets 54, 56. The torque required to turn the blade in the magnetic fluid in chamber 22, under the influence of the magnetic field, was measured. The results of the test are shown in Fig. 7.
  • the current flow in amp-turns is plotted along the X axis.
  • the current employed varied from zero to about three and one-half amps (3129 amp turns).
  • the resistance to turning of the blade 44 in terms of Pa [pounds per square inch] is given along the Y axis and varied from about zero to about 344,74 ⁇ 103 Pa (50 psi). This measurement was obtained by dividing the pounds of torque required to turn the blade by the blade surface area exposed to the magnetic responsive fluid in chamber 22. Also measurements were taken at different frequencies of oscillation varying from 0.5 Hertz to 5 Hertz.
  • the resistance to turning at zero current was nearly zero indicating excellent lubricating properties of the composition of the present invention.
  • the resistance to turning increased rapidly with increase in current flow up to about 262 ⁇ 103- 330,95 ⁇ 103 Pa (38-48 pounds per square inch) at 3129 amp-turns (about 3 1/2 amps).
  • the measurements were taken at different frequencies and all measurements followed quite similar curves indicating that the composition of the present invention is relatively frequency insensitive.
  • a conventional magnetic field responsive fluid would require currents of substantially greater magnitude to achieve equivalent coupling strength. That is, a conventional magnetic field responsive rheological fluid might provide a coupling strength of less than 6,89476 103 Pa (one pound per square inch) with a magnetic field generated with a current flow of about 3129 amp-turns.
  • the rheological fluid of the present invention permits the construction of very compact, magnetic field responsive fluid devices having a relatively high coupling strength.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Soft Magnetic Materials (AREA)
  • Lubricants (AREA)

Claims (10)

  1. Composition rhéologique de fluide sensible à un champ magnétique, ladite composition de fluide comprenant un porteur à base d'huile et une matière solide particulaire suspendue dans ledit porteur, caractérisée en ce que ladite matière particulaire est un fer-carbonyle réduit électriquement isolant, présent dans ladite composition en quantité suffisante pour donner à ladite composition des propriétés magnétiques.
  2. Composition de fluide suivant la revendication 1, dans laquelle ledit fer-carbonyle possède une taille de particule dans une gamme de 3 à 6 microns.
  3. Composition de fluide suivant la revendication 1, dans laquelle le porteur à base d'huile constitue 15 à 55 pour cent en poids du mélange de porteur à base d'huile et le fer carbonyle constitue 85 à 45 peur cent en poids du mélange de porteur à base d'huile et du fer-carbonyle.
  4. Composition de fluide suivant la revendication 1, dans laquelle l'isolement du fer-carbonyle est constitué par une couche de silice et le contenu en carbone dudit fer est de moins de 0,1 pour cent en poids.
  5. Composition de fluide suivant la revendication 1, dans laquelle ladite composition comporte un dispersant pour disperser la matière particulaire magnétisable partout dans le porteur à base d'huile, ledit porteur à base d'huile étant la phase continue de la composition, et dans laquelle ledit dispersant comporte des particules fibreuses de carbone dont les fibres ont une relation longueur-à-diamètre dans la gamme d'environ 10:1 à 1000:1, et dans laquelle ledit porteur à base d'huile possède une viscosité dans la gamme d'environ 1 à 1000 centipoises à 37,78°C (100°F).
  6. Composition de fluide suivant la revendication 5, dans laquelle ladite composition comporte:
    ledit fer-carbonyle réduit électriquement isolant et ledit dispersant dans une relation d'environ 0,5 à 10 pour cent en poids dudit dispersant à environ 90 à 99,5 pour cent en poids dudit fer-carbonyle; et
    ledit porteur à base d'huile comporte environ 15 à 25 pour cent en poids du poids combiné de fer-carbonyle et de dispersant.
  7. Composition de fluide suivant la revendication 1, dans laquelle ledit fer-carbonyle réduit et isolant comporte du fer-carbonyle réduit isolé par un silice.
  8. Composition de fluide suivant la revendication 1, dans laquelle ladite composition de fluide comporte en outre un dispersant, ledit dispersant comportant des particules fibreuses de carbone dont les fibres possèdent une relation longueur-à-diamètre dans la gamme d'environ 10:1 à environ 1000:1 ainsi qu'une aire de surface d'environ 300 mètres carrés par gramme.
  9. Composition de fluide suivant la revendication 8, dans laquelle ledit fer-carbonyle réduit et isolant comporte du fer-carbonyle réduit isolé par un silice.
  10. Composition de fluide suivant la revendication 8, dans laquelle ladite composition de fluide comporte en outre ledit fer-carbonyle et dispersant dans une relation d'environ 90 à 99,5 pour cent en poids dudit fer-carbonyle à environ 10 à 0,5 pour cent en poids dudit dispersant, et ledit porteur à base d'huile dans la proportion d'environ 15 à 50 pour cent en poids basée sur le poids combiné du fer-carbonyle et du dispersant.
EP90112257A 1989-06-27 1990-06-27 Fluide pouvant répondre à l'influence d'un champ magnétique Expired - Lifetime EP0406692B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US37229389A 1989-06-27 1989-06-27
US372293 1989-06-27

Publications (3)

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EP0406692A2 EP0406692A2 (fr) 1991-01-09
EP0406692A3 EP0406692A3 (fr) 1991-01-16
EP0406692B1 true EP0406692B1 (fr) 1994-04-20

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EP (1) EP0406692B1 (fr)
JP (1) JPH0782925B2 (fr)
DE (1) DE69008254T2 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4131846A1 (de) * 1991-09-25 1993-04-01 Basf Ag Magnetorheologische fluessigkeit
US5354488A (en) * 1992-10-07 1994-10-11 Trw Inc. Fluid responsive to a magnetic field
CA2148000C (fr) * 1992-10-30 2000-10-10 Keith D. Weiss Matieres magnetorheologiques thixotropes
JP3323500B2 (ja) * 1992-10-30 2002-09-09 ロード・コーポレーション 低粘度磁気レオロジー材料
RU2115967C1 (ru) * 1992-10-30 1998-07-20 Лорд Корпорейшн Магнитореологический материал
US5578238A (en) * 1992-10-30 1996-11-26 Lord Corporation Magnetorheological materials utilizing surface-modified particles
DE10333703B4 (de) * 2002-07-24 2007-04-26 Völkl Tennis GmbH Ballspielschläger
CN100427513C (zh) 2002-08-19 2008-10-22 宇部兴产株式会社 可用于α－烯烃的聚合或共聚的α－烯烃聚合或共聚用催化剂、其催化剂成分以及使用该催化剂的α－烯烃的聚合方法
US8282852B2 (en) 2009-09-16 2012-10-09 GM Global Technology Operations LLC Magnetorheological fluid and method of making the same

Citations (1)

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US5167850A (en) * 1989-06-27 1992-12-01 Trw Inc. Fluid responsive to magnetic field

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US1714683A (en) * 1927-08-26 1929-05-28 Bell Telephone Labor Inc Electrical insulation
US2503947A (en) * 1947-03-10 1950-04-11 Comm Engineering Pty Ltd Method of molidng magnetic powder
US2597276A (en) * 1949-06-01 1952-05-20 Gen Aniline & Film Corp Insulation of ferromagnetic particles
US2661596A (en) * 1950-01-28 1953-12-08 Wefco Inc Field controlled hydraulic device
DE2329318A1 (de) * 1973-06-08 1975-01-02 Guenther Dipl Phys Dibus Magnetische teilchen und verfahren zu ihrer herstellung
US4604229A (en) * 1985-03-20 1986-08-05 Ferrofluidics Corporation Electrically conductive ferrofluid compositions and method of preparing and using same
JP2565857B2 (ja) * 1986-12-26 1996-12-18 ティーディーケイ株式会社 磁性流体の製造方法

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US5167850A (en) * 1989-06-27 1992-12-01 Trw Inc. Fluid responsive to magnetic field

Also Published As

Publication number Publication date
JPH0782925B2 (ja) 1995-09-06
EP0406692A2 (fr) 1991-01-09
EP0406692A3 (fr) 1991-01-16
JPH0370103A (ja) 1991-03-26
DE69008254T2 (de) 1994-08-04
DE69008254D1 (de) 1994-05-26

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