Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-02-13
2001-10-02
Snow, Walter (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207220
Reexamination Certificate
active
06297629
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a device for measuring the rotation of a rotating element and, more particularly to a device that contains a magnetic encoder to be maintained in the vicinity of a sensor.
Conventionally, devices for measuring the angular position or the speed of a rotating element contain a sensor, which is maintained immobile with respect to the measurement reference frame, and a magnetic encoder driven in rotation by the shaft, the sensor cooperating with the magnetic encoder in order to provide a signal to an electronic station that processes the information. Such devices have the disadvantage of requiring an air gap between the magnetic encoder and the sensor. A variation of the air gap, for example in the case of extensive vibrations of the rotating element, can lead to incorrect information.
In order to remedy this difficulty, a known method is to use a means of application, such as an elastic washer, in order to maintain the magnetic encoder in close proximity to the sensor. An example of this type of device is described and represented in the document FR-A-2 688 606 submitted by the applicant. However, this solution leads to a rather complex device, which contains numerous pieces to be assembled, thus generating a large space requirement and a high cost of the device, which makes it poorly suited to the simplest applications.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. An object of the present invention is therefore to propose a device for measuring the rotation of a rotating element which has a small space requirement and which ensures good positioning and maintaining of a constant air gap between the magnetic encoder and the sensor and which is simple and economical to realize. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
In one aspect of the invention, this is accomplished by providing a device for measuring the rotation of a rotating element, comprising a magnetic encoder which turns with the rotating element and a sensor integrated with a support which is immobilized with respect to the rotating element. The magnetic encoder is maintained in close proximity to the sensor by magnetic application means comprising the magnetic encoder and the support, the support being produced, at least partially, from magnetic material.
REFERENCES:
patent: 4839591 (1989-06-01), Nomura et al.
patent: 5081756 (1992-01-01), Abe et al.
patent: 5157329 (1992-10-01), Brauer
patent: 5635833 (1997-06-01), Onodera et al.
Bigler John C.
Snow Walter
The Torrington Company
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