Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-12-15
2001-10-30
Williams, Hezron (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200, C324S207220
Reexamination Certificate
active
06310473
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the field of rotational position sensors, and more specifically to a magnetic rotational position sensor for sensing each rotational position of a control shaft about a rotational axis over a definable range of rotation.
Electronic fuel injected engines used in motor vehicles typically embody a microprocessor based control system. Fuel is metered or injector activation time is varied in accordance with various engine parameters including the regulation of air flow into the engine via a rotational position of a throttle diaphragm relative to a closed position of the throttle diaphragm. Typically, a shaft is adjoined to the throttle diaphragm to synchronously rotate the throttle diaphragm as the shaft is rotated between the closed position and a maximal open position of the throttle diaphragm. Rotational position sensors are adjoined to or adjacent the shaft to sense each rotational position of the shaft, i.e. each degree of rotation of the shaft relative to the closed position, thereby the rotational position of the throttle diaphragm relative to the closed position is sensed.
One of the problems associated with prior contact rotational position sensors that incorporate a contact element, e.g. a contact potentiometer, is the wear and tear experienced by the contact element that reduces the useable life of the contact rotational position sensor. One of the problems associated with prior magnetic rotational position sensors is magnetic hysteresis. Magnetic hysteresis causes an offset error signal to be generated whenever a magnet of the sensor is advanced from and returned to a reference position of the magnet, or whenever a magnetizable component of the sensor, e.g. a magnetizable pole piece, is advanced from or toward the magnet of the sensor. Annealing the magnet can minimize, but never eliminate, magnetic hysteresis. What is therefore needed is a novel and unique magnetic rotational position sensor that neither incorporates a contact element nor experiences magnetic hysteresis.
SUMMARY OF THE INVENTION
The present invention is a magnetic rotational position sensor for sensing each degree of rotation of a control shaft about a first rotational axis over a definable range of rotation. The present invention overcomes the aforementioned drawbacks associated with prior contact rotational position sensors and prior magnetic rotational position sensors. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention described in detail herein can only be determined with reference to the claims appended hereto, certain features which are characteristic of the present invention disclosed herein can be described briefly.
Each embodiment of a magnetic rotational position sensor in accordance with the present invention comprises a loop pole piece, one or more magnets, and one or more magnetic flux sensitive transducers. The loop pole piece includes a plurality of pole pieces serially adjoined in a closed configuration to define an air gap area. One or more pole pieces of the loop pole piece has an inner diameter surface radially extending from a second rotational axis. Each magnet has a north pole surface and a south pole surface to generate magnetic flux.
A magnet is disposed within the air gap area of the loop pole piece with each pole surface of the magnet facing either the inner diameter of a pole piece of the loop pole piece or a pole surface of another magnet disposed within the air gap area to enclose the magnetic flux from the magnet(s) within the loop pole piece to thereby establish a magnetic field throughout the air gap area. The loop pole piece and the magnet(s) are adjoined to the control shaft to synchronously rotate about the second rotational axis over the definable range of rotation as the control shaft is rotated about the first rotational axis over the definable range of rotation. Thus, each degree of rotation of the control shaft about the first rotational axis over the definable range of rotation exclusively corresponds to a distinct degree of synchronized rotation of the magnetic field about the second rotational axis over the definable range of rotation.
In a first aspect of the present invention, a pole surface of a magnet disposed within the air gap area spatially faces an inner diameter surface of a pole piece of the loop pole piece to define a working air gap area therebetween. The pole surface of the magnet, and the inner diameter surface of the pole piece are contoured to arcuately configure the working air gap area. In a second aspect of the present invention, a pole surface of a first magnet disposed within the air gap area spatially faces a pole surface of a second magnet disposed within the air gap area to define a working air gap area therebetween. The pole surface of the first magnet, and the pole surface of the second magnet are contoured to arcuately configure the working air gap area.
Each magnetic flux sensitive transducer is operable to sense a magnetic flux density of any magnetic flux passing through the magnetic flux sensitive transducer. A magnetic flux sensitive transducer is disposed within each working air gap area. The arcuate configuration of the working air gap area enables the magnetic flux sensitive transducer to be operable to sense a different magnitude of magnetic flux density for each degree of synchronously rotation of the control shaft and the magnetic field over a definable range of rotation.
It is a primary object of the present invention to sense each rotational position of the control shaft about the rotational axis over the definable range of rotation without experiencing magnetic hysteresis by synchronously rotating the loop pole piece, and the magnet(s) about the second rotational axis as the control shaft rotates about the first rotational axis.
Further objects, features, and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.
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Andersen Henry S.
Kearney-National Inc.
Williams Hezron
Woodhard, Emhardt, Naughton, Moriarty & McNett
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