Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
1998-07-24
2001-01-30
Strecker, Gerard (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S249000, C033S361000, C336S200000, C336S221000, C336S229000
Reexamination Certificate
active
06181130
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a magnetic sensor for detecting a weak magnetic field as a stray magnetic field generated in an automobile, a ship, an aircraft, a domestic electrical appliance, a medical instrument, and the like.
A conventional magnetic sensor comprises a toroidal inductor accommodated in a bobbin having at least one detection coil wound thereon. The toroidal inductor comprises a ring-shaped or toroidal core contained in a ring-shaped core case on which a toroidal coil as an excitation coil is wound.
The magnetic sensor is a transformer. When an exciting AC voltage as a primary voltage is applied to the excitation coil, AC magnetic fluxes are induced to flow in the toroidal core. Therefore, a secondary voltage as an output voltage is induced on the detection coil. When the stray magnetic field is applied to the toroidal core, the AC magnetic fluxes flowing in the toroidal core are affected by the stray magnetic field and change. As a result, the output voltage is changed in the amplitude. That is, the output voltage is amplitude-modulated by the stray magnetic field. Therefore, the stray magnetic field can be detected from the amplitude variation of the output voltage.
Manufacture of the above-mentioned magnetic sensor requires troublesome winding operations for forming the excitation coil and at least one detection coil. Particularly, in the winding operation for the excitation coil, a wire must be wound on the toroidal core, actually the ring-shaped core case to form the toroidal excitation coil. This winding operation is quite troublesome because the wire is made to repeatedly pass through an inner bore of the ring-shaped core case until it is wound around the core case by the number of turns ranging from several tens to several hundreds. Thus, it takes a long time for such a winding operation.
If the toroidal inductor has a small size, the inner bore of the ring-shaped core case has a small diameter. In this event, it becomes difficult to perform the winding operation for making the wire pass through the inner bore of the ring-shaped core case. The result is that miniaturization of the toroidal inductor is limited.
Recently, there are available in commerce small-sized magnetic sensors using printed circuit boards stacked holding a relatively thin toroidal core therebetween. The printed circuit boards have, as thin conductor patterns, sections of excitation coils and detection coils. Those sections are connected to one another through through-holes in the circuit boards to thereby form those coils.
Although the known magnetic sensor of the printed circuit type is formed in a small size, it is low in reliability. This is because that the thin toroidal core is readily deformed and/or destroyed by mechanical strain of printed circuit boards caused by undesired external force applied to the printed circuit boards.
In the printed type magnetic sensor, it is impossible to use a bulk type toroidal core which has a relatively large axial size. Further, the toroidal core is badly affected by heat during the reflowing operation to solder the conductor patterns of the printed circuit boards.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a small-sized magnetic sensor with excellent reliability wherein a toroidal core is protected from external forces, and no winding operation is required for an excitation coil.
It is another object to provide a magnetic sensor having a structure which is capable of using a toroidal core which is a bulk type having a relatively large axial size.
It is another object of this invention to provide a magnetic sensor which is simple in structure, reduced in the number of components, easy to produce and therefore, low in cost.
It is yet another object of this invention to provide a high-performance magnetic sensor which is capable of preventing a magnetic core from being influenced by heat such as by soldering upon bonding of conductive patterns and is therefore capable of detecting a weak magnetic field with high accuracy.
According to this invention, there is provided a magnetic sensor comprising a bobbin, a toroidal inductor mounted within the bobbin, the toroidal inductor comprising a toroidal magnetic core and an excitation toroidal coil wound around the toroidal core, and at least one detection coil wound on the bobbin, wherein the bobbin comprises a bobbin case having a toroidal groove accommodating the toroidal inductor and a bobbin cover coupled to the bobbin case to cover the toroidal groove. One of the bobbin case and the bobbin cover has a conductor pattern, the conductor pattern comprising a plurality of angularly speed, radially extending thin-film linear conductors each having a radial inner end and a radial outer end. A plurality of connecting conductors radially extend over the toroidal magnetic core to connect the radial inner end of a corresponding one of the thin-film linear conductors to the radial outer end of an adjacent one of the thin-film linear conductors so that the excitation toroidal coil is formed by the conductor pattern and the connecting conductors.
According to an embodiment, the conductor pattern is formed on the bobbin case to radially extend from an inside to an outside of the toroidal groove, the connecting conductors being wires, and the bobbin cover being a plastic resin loaded on the bobbin case to cover the connecting conductors, the toroidal core and the conductor patterns together.
According to another embodiment, the conductor pattern is formed on the bobbin case to radially extend from an inside to an outside of the toroidal groove, the bobbin cover being a printed circuit board having the connecting conductors as another conductor pattern formed thereon.
According to another embodiment, the bobbin cover is a printed circuit board having the conductor pattern, the connecting conductors being connecting wires, thus, the toroidal inductor being fixedly mounted on the bobbin cover and being accommodated within the toroidal groove in the bobbin case.
REFERENCES:
patent: 3483497 (1969-12-01), Clark et al.
patent: 4103267 (1978-07-01), Olschewski
patent: 4825166 (1989-04-01), MacGugan
patent: 4907346 (1990-03-01), Watanabe
patent: 4967156 (1990-10-01), Seitz
patent: 5191699 (1993-03-01), Ganslmeier et al.
patent: 5430613 (1995-07-01), Hastings et al.
patent: 35 5 19 609 A1 (1986-12-01), None
patent: 0175069 A1 (1986-03-01), None
patent: 0473875 A1 (1992-03-01), None
patent: 0490438 A1 (1992-06-01), None
patent: 9-5083 (1997-01-01), None
patent: WO 93/08450 (1993-04-01), None
“High Manufacturability, Low Cost Torroidal Inductor”, IBM Technical Disclosure Bulletin, vol. 32, No. 4B, Sep. 1, 1989, pp. 323-324.
Patent Abstracts of Japan, vol. 018, No. 290 (E-1557), Jun. 2, 1994 & JP 06 061055 A (Toyota Autom Loom Works, Ltd.) Mar. 4, 1994.
Patent Abstracts of Japan, vol. 017, No. 188 (E-1349), Apr. 13, 1993 & JP 04 337610 A (Fujitsu Ltd), Nov. 25, 1992.
Patent Abstracts of Japan, vol. 097, No. 005, May 30, 1997 & JP 09 005083 A (Tokin Corp.), Jan. 10, 1997.
Hoshi Norimitsu
Sato Naoyuki
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Strecker Gerard
Tokin Corporation
LandOfFree
Magnetic sensor having excitation coil including thin-film... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic sensor having excitation coil including thin-film..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic sensor having excitation coil including thin-film... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2479988