Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1998-04-29
2001-05-08
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
Reexamination Certificate
active
06227710
ABSTRACT:
The present invention relates to the field of rolling bearings with information sensors of the kind possessing a stationary race and a rotating race, one or more rows of rotating elements in contact with raceways formed on the said races, a sensor assembly secured to the stationary race and an encoder means secured to the rotating race and rotating past the sensor with a radial gap.
This type of rolling bearing is used in numerous applications where it is necessary to have accurate information about the angular displacement parameters of a mechanical element, especially the speed or angular position. These rolling bearings can be used for example in electric motors, robots or in numerous rotating members.
One of the problems to be solved in this type of instrumented rolling bearing is the accuracy obtained with regard to the value of the radial gap between the sensor and the encoder, the quality and reliability of the signal obtained depending on this parameter. The accuracy in the value of the gap depends in particular on the concentricity of the races of the rolling bearing, on the concentricity of the encoder with respect to the rotating race and on the radial position of the sensor with respect to a reference surface of the non-rotating race. The concentricity of the races of the rolling bearing is achieved by construction, a rolling bearing being a precision mechanical member. The concentricity of the encoder with respect to the rotating race of the rolling bearing poses no particular problem insofar as the annular encoder can be push-fitted onto a precision-ground land of the rotating race. The radial position of the sensor with respect to a reference surface of the non-rotating race of the bearing, therefore remains the determining parameter with regard to the final accuracy in the value of the gap.
In conventional systems, the electronic component constituting the sensor is fixed in a support, generally made of a synthetic material, so as thus to form a sensor block which is itself positioned on the non-rotating race of the instrumented rolling bearing. It follows that the accuracy of the gap between the sensor and the encoder will depend largely on the accuracy with which the sensor can be positioned radially with respect to its support and with which the support can be positioned radially with respect to a reference surface of the non-rotating race of the rolling bearing. This results, on the one hand, in a relatively high manufacturing cost and, on the other hand, in additional risks regarding the scatter in the final value of the resulting gap between the sensor and the encoder.
The object of the invention is to overcome the drawbacks of the above devices and to propose a rolling bearing which makes it possible to circumvent the problem of the radial positioning of the sensor with respect to its support.
The rolling bearing, according to the invention, comprises a stationary race, a rotating race, at least one row of rolling elements placed between the stationary race and the rotating race, an encoder means secured to the rotating race and concentric therewith and a sensor assembly which includes a sensor and a support for the sensor. The sensor is secured to the stationary race and arranged facing and a small gap away from the encoder means the travel of which, during rotation, is detected by the which bears directly on a reference surface of the stationary race.
The scatter in the value of the gap, due to the positioning of the sensor with respect to its support and of the support with respect to the stationary race, is thus eliminated.
Advantageously, there is provision for the support to exert a continuous load on the sensor in the direction of the reference surface. This load precludes any inopportune displacement of the sensor.
In one embodiment of the invention, the sensor comprises at least one magnetosensitive sensor, for example a Hall effect sensor, or optical sensor and the encoder means comprises a multipole magnetized ring.
In one embodiment of the invention, the sensor assembly includes at least one of which, each sensor is provided with a housing comprising a reference face in contact with the said reference surface of the stationary race, and a detection face opposite the reference face and arranged facing the encoder means.
Preferably, the housing comprises two chamfer-forming oblique surfaces linking up with each side of the detection face. The sensor support can be annular and provided with at least one recess designed to accommodate a sensor, each recess comprising a notch whose edges form surfaces for positioning the sensor with respect to the support. Advantageously, the edges of the recess are arranged converging towards the inside of the bearing, and in contact with the oblique surfaces of the housing.
In one embodiment of the invention, the support comprises at least one drilling for connection pins of the sensor.
Advantageously, the support comprises an annular main body and an annular retaining element, the main body being in contact with the front end face of the extension and the retaining element being in contact with the bore of the said extension.
In one embodiment of the invention, the reference face of the housing projects radially with respect to the periphery of the support.
In one embodiment of the invention, the support is provided with two axial grooves capable of co-operating with complementary surfaces of the stationary race.
In this way one or more sensors are obtained whose spatial position is determined directly by their contact with the reference surface of the stationary race, thus considerably reducing the possibilities of scatter in the value of the gap between the sensor and the encoder.
REFERENCES:
patent: 4875785 (1989-10-01), Santos et al.
patent: 0320322A (1989-06-01), None
patent: 0495323A (1992-07-01), None
patent: 0511105A (1992-10-01), None
patent: 0631139A (1994-12-01), None
Landrieve Franck
Message Olivier
Footland Lenard A.
SKF France
Smith Gambrell & Russell
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