Inductor devices – With electric and/or magnetic shielding means
Reexamination Certificate
1999-07-20
2001-08-07
Donovan, Lincoln (Department: 2832)
Inductor devices
With electric and/or magnetic shielding means
C336S120000
Reexamination Certificate
active
06271741
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to rotary electrical couplings and in particular rotary inductive couplings for transmitting a low level electrical signal and/or an electrical power signal across a rotating junction.
Rotary couplings are useful where it is desired to conduct electrical signals from a stationary to a rotating member or as between two relatively rotating members.
In motor vehicles it has been the practice to provide slip rings, rotary wiper contacts or a ribbon of parallel electrical conductors with the ribbon spirally wound in the form of a “clock spring” for electrically connecting accessory switches and the vehicle horn button in addition to supplying the energy to the steering wheel mounted airbag inflator for effecting inflation in a steering column/steering wheel air bag installation. However, slip rings, wipers and clock spring conductors have proven to be noisy, costly and extremely difficult to assemble for high volume mass production of vehicles. Therefore, it has been desired to provide a relatively frictionless, simpler and lower cost alternative for connecting electrical controls and devices mounted on the steering wheel to the vehicle wiring harness.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a solution to the above-described problem of providing an electrical coupling for a rotary junction and employs an inductive coupling comprising a transformer having one coil or stator stationary with the other coil or rotor relatively rotatable with respect to the stationary coil. The rotary transformer coupling of the present invention is particularly suitable for providing an electrical coupling across the junction of an automotive steering wheel and the steering column to provide electrical connection of the switches and accessories mounted on the steering wheel to the vehicle circuitry; and, its construction is relatively low in manufacturing cost.
The rotary transformer of the present invention has a coiled conductor wound on a bobbin which is subsequently overmolded or inserted into a magnetically permeable material dispersed in a non-magnetic medium to form an annular stator. A second coiled conductor is wound on a second bobbin and subsequently overmolded with magnetically permeable material disbursed in a non-magnetic medium to form an annular rotor.
Alternatively, the magnet wire may have a heat bondable jacket or coating enabling the wire to be wound on a mandrel to form a coil, the mandrel removed and the wire coating heat fused to form a free standing coil, thereby eliminating the bobbin. The stator and rotor are disposed coaxially in side-by-side arrangement to form a transformer. In a steering column application, the stator is mounted on the column and the rotor mounted on the steering wheel. The stator and rotor have a particularly high density of magnetic permeability for the volume of the stator and rotor and thus enables the transformer of the present invention to be employed in a motor vehicle steering column application where it is required to transmit substantial current at the vehicle power supply voltage, typically 12 volts, for providing the current to activate the firing squib in the airbag inflator.
The rotary transformer of the present invention in one embodiment has a plurality of axially extending projections molded integrally with the magnetically permeable material in the non-magnetic medium on either the stator or the rotor; and, a circuit board having cut-outs therein is received over the projections and retained thereon for providing associated electrical componentry utilized in the application with the transformer. The transformer of the present invention thus is easily manufactured at a relatively low cost and is compact and provides a high efficiency or magnetic density inductive coupling and can provide the requisite current carrying capacity needed for an automotive steering column airbag inflator application.
REFERENCES:
patent: 3872334 (1975-03-01), Loubier
patent: 3924174 (1975-12-01), Fahrner
patent: 4259603 (1981-03-01), Uchiyama et al.
patent: 4514645 (1985-04-01), Endo et al.
patent: 5347256 (1994-09-01), Yumiki et al.
patent: 5856710 (1999-01-01), Baughman et al.
patent: 55-23712 (1980-02-01), None
Donovan Lincoln
Eaton Corporation
Johnston Roger A.
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