Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1999-11-23
2001-06-19
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S174000
Reexamination Certificate
active
06249118
ABSTRACT:
TECHNICAL FIELD
The present invention relates to automotive sensors.
BACKGROUND OF THE INVENTION
In many of today's vehicles, sensors that sense a rotating target wheel may be used for different applications. For example, a target wheel may be engaged with a vehicle crankshaft for inducing signals in one or more sensors positioned next to the target wheel, with the signals representing the angular position of the crankshaft. These position signals can be used in distributorless ignition systems that have selectively energized ignition coils that fire the spark plugs as appropriate for the angular position of the crankshaft. Moreover, the crankshaft angular position signals can be used for combustion control and diagnostic functions.
Essentially, the edge of the disk-shaped wheel is varied along the periphery of the wheel in some fashion, e.g., by cutting slots in the periphery in a predetermined pattern. Usually, one or two sensors are used to detect the slots as they pass by the sensors, with the detected slot pattern being correlated to a crankshaft angular position and, when two sensors are used, also to a crankshaft direction of rotation. Unfortunately, the present state of the art sensors of the above variety may be expensive and, in turn, increase manufacturing and production costs. The present invention has recognized the above-noted problems and has provided the below solutions to one or more of the above-noted problems.
SUMMARY OF THE INVENTION
A target wheel sensor works in conjunction with a rotating target wheel that has at least one tooth. The sensor includes a hollow housing and a sensing structure that is disposed within the housing. As described below, the sensing structure includes a magnet and a pole piece magnetically coupled to each other and slidably disposed within the housing. Accordingly, the magnet and pole piece are movable in unison between a retracted position, wherein the pole piece is distanced from the tooth, and an extended position, wherein the pole piece is closely spaced from the tooth.
As envisioned in the particularly preferred embodiment set forth below, the sensing structure includes a T-shaped spool that has a pole piece holder that terminates in a magnet holder. Preferably, the pole piece and the magnet are slidably engaged with the pole piece holder and the magnet holder, respectively.
Also in a preferred embodiment, the sensor includes a coil disposed around the pole piece holder and a means for biasing the pole piece and the magnet toward the retracted position. In a preferred embodiment, this means may be a spring disposed in compression between the magnet and the coil.
Additionally, in a preferred embodiment described below, the housing includes an open distal end and the sensor includes a sealing disk extending radially outward around the pole piece holder to seal the open distal end of the housing. Furthermore, the sensor housing defines an axis, and the target wheel defines a center that is aligned with the sensor housing axis.
In another aspect of the present invention, a position sensing apparatus includes a rotatable target wheel having at least one tooth. A position sensor includes a housing having a distal end juxtaposed with the target wheel and a magnetic assembly slidably disposed in the housing. The magnetic assembly is biased toward a retracted position, wherein the magnetic assembly is disposed at a proximal location in the housing, and an extended position, wherein the magnetic assembly is disposed at a distal location in the housing.
In yet another aspect of the present invention, a target wheel sensor is used to sense a rotating target. This is accomplished by providing a rotating target wheel that has at least one tooth and a center. Also, a sensor is provided that includes a hollow housing that defines an axis and that includes a sensing structure disposed in the housing. The sensing structure includes a pole piece that is slidably disposed within the housing and is movable between a retracted position relative to the target wheel and an extended position relative to the target wheel. In this aspect of the present invention, the sensor is installed in proximity to the target wheel so that the center of the target wheel is aligned with the sensor housing axis.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
REFERENCES:
patent: 5229715 (1993-07-01), Niino et al.
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Patidar Jay
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