Package for speed sensing device having minimum air gap
First Claim
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1. A rugged magnetic sensor assembly which includes a housing having an opening for receiving a magnetic sensing unit, said sensor assembly comprising:
- a prepackaged magnetic sensing unit which is not sufficiently rugged to be used in a given application, said sensing unit having first and second external surface areas and comprised of an encapsulated sensing device having electrical leads, wherein the encapsulation is not adequately protective of the electrical lead areas of said prepackaged sensing unit, said first external surface being a sealing surface and said second external surface being proximate said sensing device;
a housing having an opening therein adapted to cooperatively receive said sensing unit;
said sensing unit of size and shape complementary to said housing opening, effective to be at least partially received in said opening of said housing;
said sensor unit at least partially disposed within said opening and having said first exterior surface cooperatively disposed with respect to an interior surface of said housing, which interior surface defines said opening in said housing, and leaving said second exterior surface exposed outside said housing; and
means for sealing said exterior surface on said sensing unit against said interior surface of said housing;
wherein said sealing means, external surface of said sensing unit, and said interior surface of said housing define an enclosure for retaining said sensing unit in fixed position and for protecting said electrical lead areas of said sensing unit from deleterious environmental effects of said given application, and wherein portions of said housing do not overlie said second surface portion of said sensing unit and thereby substantially decrease magnetic sensitivity of said sensing unit.
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Abstract
A magnetic field sensing device in the form of a sensor unit which reduces the effective air gap between the sensing device and its exciter is provided by packaging the sensing device in the manner that provides protection from the environment while simultaneously minimizing the distance between the sensing device and its exterior surface adjacent its exciter. The present invention is particularly suitable for automotive applications, such as magnetic field sensing devices for detecting the wheel speed for an electronic anti-lock braking system.
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Citations
22 Claims
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1. A rugged magnetic sensor assembly which includes a housing having an opening for receiving a magnetic sensing unit, said sensor assembly comprising:
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a prepackaged magnetic sensing unit which is not sufficiently rugged to be used in a given application, said sensing unit having first and second external surface areas and comprised of an encapsulated sensing device having electrical leads, wherein the encapsulation is not adequately protective of the electrical lead areas of said prepackaged sensing unit, said first external surface being a sealing surface and said second external surface being proximate said sensing device; a housing having an opening therein adapted to cooperatively receive said sensing unit; said sensing unit of size and shape complementary to said housing opening, effective to be at least partially received in said opening of said housing; said sensor unit at least partially disposed within said opening and having said first exterior surface cooperatively disposed with respect to an interior surface of said housing, which interior surface defines said opening in said housing, and leaving said second exterior surface exposed outside said housing; and means for sealing said exterior surface on said sensing unit against said interior surface of said housing; wherein said sealing means, external surface of said sensing unit, and said interior surface of said housing define an enclosure for retaining said sensing unit in fixed position and for protecting said electrical lead areas of said sensing unit from deleterious environmental effects of said given application, and wherein portions of said housing do not overlie said second surface portion of said sensing unit and thereby substantially decrease magnetic sensitivity of said sensing unit. - View Dependent Claims (2, 3, 4, 5)
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6. A magnetic sensor assembly which includes a housing having a pre-molded inner member, an overmolded outer member, and said inner member having an opening for receiving a pre-packaged magnetic sensor unit, said sensor assembly comprising:
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a prepackaged magnetic sensing unit having first and second external surface areas and comprised of an encapsulated sensing device having electrical lead areas that are to be isolated from an environment to which said encapsulation is to be exposed, said first external surface being a sealing surface and said second external surface being proximate said sensing device; a first housing member having an opening therein adapted to cooperatively receive said sensing unit, including electrical leads of said sensing unit, and containing electrical connector means; said sensing unit of size and shape complementary to said housing opening, effective to be at least partially received in said opening of said housing; said sensing unit at least partially disposed within said opening and having said first exterior surface cooperatively disposed with respect to an interior surface of said housing, which interior surface defines said opening in said housing, and leaving said second exterior surface exposed outside said housing; said sensing unit electrical leads protectively disposed within said first housing member and connected to said electrical connector means of said first housing member; a second housing member overmolded around said first housing member but not said second external surface of said sensing device; and means for sealing said exterior surface on said sensing unit against said interior surface of said housing; wherein said sealing means, and said first and second housing members provide an assembly for retaining said sensing unit in fixed position and for protecting said electrical lead areas of said sensing unit from deleterious environmental effects of said given application without substantially decreasing magnetic sensitivity of said sensing unit. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A sensor assembly for sensing a highly magnetically permeable target, said sensor assembly comprising a circular disk-like sensing unit disposed within a circular opening in a housing but still exposed outside of said housing, said sensor assembly comprising:
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a sensing unit having electrical leads and a circular disc-shaped pre-molded encapsulation sized to be received in a circular opening in a housing member and at least partially contained in said housing member, said encapsulation having an exterior surface formed on a first axial end surface, a second axial end surface opposite said exterior surface, and a cylindrical radial surface spacing said axial end surfaces, said first axial end surface disposed in said housing for spacing from a high magnetic permeable target when said sensing unit is received within said housing opening; a housing member having an opening therein sized to receive said sensing unit, including its electrical leads, electrical contact leads affixed within said housing and electrically connected to said electrical leads on said sensing unit, said housing electrical contact leads integrally formed with and extending from said housing; a circumferential groove formed in said cylindrical radial surface of said housing; and resilient sealing means disposed in said groove for sealing between said sensing unit encapsulation and said opening of said housing, and for retaining said sensing unit in said opening of said housing; wherein said sensing unit encapsulation is left partially exposed but which forms an enclosure with said housing for protecting electrical lead areas of said sensing unit. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification