Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-12-01
2001-02-20
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207210
Reexamination Certificate
active
06191579
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to magnetic position sensors and more particularly to magnetic field concentrators employed in a rotary magnetic sensor.
BACKGROUND OF THE INVENTION
For mechanisms having one portion that rotates relative to another, it is often necessary to know the precise relative rotational position between the two portions. There are many types of sensor arrangements that can accomplish such a task; however, many have drawbacks in that they are too large for a particular application, too expensiv e to design and fabricate, or require extensive calibration once assembled in the mechanism.
These types of sensors can be used, for example as throttle position sensors, fuel accumulators, transmission position sensors, steering angle sensors, and gear tooth sensors. Many other types of applications of course can also benefit from having rotational position sensing.
Also, of course, it is desirable that the sensor be as inexpensive and easy to fabricate and assemble as possible in order to minimize the cost of the sensor assembly.
An additional requirement for some positional sensor applications is that there is a backup sensor or some other means of detecting a failure in part of the sensor assembly. In this way, if part of the sensor does fail, the appropriate actions can be taken to assure that no harm is done until the sensor can be fixed or replaced.
Consequently, it is desirable to have a rotational position sensor that does not need calibration, or may need only minimal calibration, is small in size, cost effective, and still reliable, with feedback if a failure of a portion of the sensor assembly occurs.
SUMMARY OF THE INVENTION
In its embodiments, the present invention contemplates a rotary position sensor assembly. The sensor assembly including a mounting base having a center of relative rotation, and magnetic means for creating a magnetic field having generally parallel magnetic flux around base, with the magnetic means having a center of relative rotation at the same location as the base. The sensor assembly also includes a sensor array having two sets of magnetic field sensors, with each sensor spaced and oriented to extend radially from the center of relative rotation, and with the sensor array including means for reducing the magnetic flux passing through each of the sensors that is more parallel to the general direction of magnetic flux produced by the magnetic means than the sensors which are relatively less parallel. Also, the sensor assembly includes means for communicating signals through each of the magnetic field sensors.
The present invention further contemplates a method for operating a rotary position sensor located in the magnetic flux of a uniform magnetic field and relatively rotatable thereto about a center of rotation, the method comprising the steps of: providing a first and a second set of radially oriented magnetic field sensors spaced circumferentially about the center of relative rotation; sensing the rotational position of a magnetic field relative to the first set of magnetic field sensors; sensing the rotational position of the magnetic field relative to the second set of magnetic field sensors; comparing the relative rotational position of the first set of sensors with the relative rotational position of the second set of sensors; and determining that a failure has occurred if the relative rotational position of the first set of sensors is not substantially equal to the relative rotational position of the second set of sensors.
Accordingly, an object of the present invention is to direct a generally uniform magnetic field across a rotary position sensor assembly such that the magnetic field strength appearing across each individual sensing element of the array is related to the direction of the magnetic field relative to that particular element.
It is a further object of the present invention to provide a redundancy to the sensor assembly so that should one of the sensor elements fail, the sensor assembly will be able to recognize such and react accordingly, without substantially increasing the cost or size of the overall sensor assembly.
An advantage of the present invention is that the magnetic flux is distributed by the concentrators in a controlled manner over multiple magnetic field sensing elements.
Another advantage of the present invention is that this sensor array can be used with various types and sizes of magnetic field sensing elements. While this invention will operate on large scale assemblies, it will also operate effectively on very small scale assemblies, including micro-scale sensors with the structure built up on a ceramic chip or on a silicon chip which may or may not also contain additional electronic components.
A further advantage of the present invention is that magnetic field direction and hence rotary sensor position can be determined by comparing the responses of the individual sensing elements in the array to each other, without the need for precise temperature and magnetic field calibration in the final assembly.
An additional advantage of the present invention is that the arrangement of the sensor array can be configured so as to make assembly and alignment of the array onto a chip easier.
Another advantage of the present invention is that different configurations of magnets, for producing a magnetic field on the sensor array, can be employed to allow for flexibility of design for the sensor assembly.
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Andersen Henry S.
Mark Mollon
Oda Christine
Visteon Global Technologies Inc.
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