Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-05-18
2001-02-13
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207250
Reexamination Certificate
active
06188216
ABSTRACT:
BACKGROUND OF THE PREFERRED EMBODIMENT(S)
1. Field of the Preferred Embodiment(s)
This invention generally relates to position sensing and to a position sensor which is compact, durable and precise. More specifically, the invention relates to a noncontacting low profile position sensor.
2. Description of the Related Art
Position sensing is used to allow an electrical circuit to gain information about an event or a continuously varying condition. There are a variety of known techniques for angular position sensing. For example, optical, electrical, electrostatic, and magnetic fields are all used in a sensor to measure position. There are many known sensors such as resistive contacting networks, inductively coupled ratio sensors, variable reluctance devices, capacitively coupled ratio detectors, optical detectors using the Faraday effect, photo-activated ratio detectors, and electrostatic ratio detectors.
There are many applications for sensors, and a wide variety of technologies to fill these needs. Each of these technologies offers a unique set of advantages and limitations. limitations. Of these technologies, magnetic sensing is known to have a unique combination of long life components and excellent resistance to contaminants.
Regardless of the arrangement and method for changing the field about the sensor, the magnetic circuit faces several obstacles which have not been overcome. Movement of the sensor relative to the gap as a result of bearing play will lead to a variation in field strength measured by the sensor. This effect is particularly pronounced in Hall effect, magneto-resistive and other similar sensors, where the sensor is sensitive about a single axis and insensitive to perpendicular magnetic fields.
DESCRIPTION OF RELATED ART
Examples of patents related to the present invention are as follows, wherein each patent is herein incorporated by reference for related and supporting teachings:
U.S. Pat. No. 3,112,464 is a hall effect translating device.
U.S. Pat. No. 4,142,153 is a tachometer for measuring speed and direction of shaft rotation with a single sensing element.
U.S. Pat. No. 4,293,837 is a hall effect potentiometer.
U.S. Pat. No. 4,570,118, is an angular position transducer including permanent magnets and hall effect device.
U.S. Pat. No. 4,726,338 is a device for controlling internal combustion engines.
U.S. Pat. No. 4,744,343 is a device for controlling an internal combustion engine.
U.S. Pat. No. 4,848,298 is a device for controlling internal combustion engine.
U.S. Pat. No. 4,942,394 is a hall effect encoder apparatus
U.S. Pat. No. 5,055,781, is a rotational angle detecting sensor having a plurality of magnetoresistive elements located in a uniform magnetic field.
U.S. Pat. No. 5,115,239 is a magnetic absolute position encoder with an undulating track.
U.S. Pat. No. 5,159,268 is a rotational position sensor with a hall effect device and shaped magnet.
U.S. Pat. No. 5,258,735 is a multi-pole composite magnet used in a magnetic encoder.
U.S. Pat. No. 5,313,159 is a magnetic encoder with composite magnet.
U.S. Pat. No. 5,712,561 is a field strength position sensor with improved bearing tolerance in a reduced space.
U.S. patent application Ser. No. 08/206982 titled, “dual magnet hall effect position sensor”, filed Mar. 4, 1994 and owned by the same assignee as the instant application.
U.S. patent application Ser. No. 08/206474 titled, “molded magnet structure”, filed Mar. 4, 1994 and owned by the same assignee as the instant application.
U.S. patent application Ser. No. 08/976879 titled, “molded magnet structure”, filed Nov. 24, 1997 and owned by the same assignee as the instant application.
U.S. patent application Ser. No. 08/206568 titled, “flux gradient control”, filed Mar. 4, 1994 and owned by the same assignee as the instant application.
U.S. patent application Ser. No. 08/659963 titled, “field strength position sensor with improved bearing”, filed Jun. 7, 1996 and owned by the same assignee as the instant application.
U.S. patent application Ser. No. 08/971800 titled, “flux gradient control”, filed Nov. 17, 1997 and owned by the same assignee as the instant application.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicants' acknowledged duty of candor in disclosing information that may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicants' claimed invention.
PROBLEMS WITH THE PRIOR ART
There are several problems that exist with the prior art that are addressed by the preferred embodiment. One problem with the prior art sensors is that they are too thick and are unable to fit into some engine locations. Engine compartments are becoming more cramped due to more engine functions being added. Another cause of engine room space shortage is the trend toward maximizing the interior space of the car while keeping the overall dimensions of the car the same. This leads to a shrinking of the engine compartment.
Another problem is that the prior art throttle position sensors have had to have a shorter input shaft that can not extend through or beyond the device. In some applications, it is preferable to have a longer shaft.
This and other problems will be solved by the preferred embodiments of the invention. A review of the specification, drawings, and claims will more clearly teach a skilled artisan of other problems that are solved by the preferred embodiments.
SUMMARY OF THE PREFERRED EMBODIMENT(S)
It is a feature of the invention to provide a position sensor for rotational engagement with a shaft. The sensor includes a pole piece, having a first and second piece, a backstrap for retaining the first and second pieces in parallel and opposing relationship, and a bore extending through at least one of the pieces for the shaft to be inserted therein. A first and second magnet is disposed on the first and second pieces respectively. A magnetic sensor is positioned between the first and second magnets.
A magnetic field varies from a first to a second location on the magnets and extends across the air gap. The magnetic field sensor is positioned in the air gap and operates to provide an output signal representative of the variable magnetic field as the pole piece is rotated. The output signal changes magnitude in relation to the relative position of the magnet with respect to the magnetic field sensor.
It is a feature of the invention to provide a first and second magnetically permeable devices with a first and second aperture or bore, respectively. The shaft passes through at least one of the first or second apertures or bore.
A further feature of the invention is to provide the magnetically permeable device to be held to the shaft by a shaft retainer.
The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. Further, the abstract is neither intended to define the invention of the application, which is measured by the claims, neither is it intended to be limiting as to the scope of the invention in any way.
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patent: 5712561 (1998-01-01)
Borgman Mark W.
Bourgeois Mark P.
CTS Corporation
Jolly Anthony
Oda Christine
LandOfFree
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