Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
1999-07-22
2001-03-27
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
C324S207200
Reexamination Certificate
active
06205866
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor device for detecting small angular position changes and, more particularly, to a sensor device for detecting angular position changes of mechanical parts that rotate relative to each other, especially those angle changes due to the torsion experienced by an axle.
2. Prior Art
From U.S. Pat. No. 5,501,110, a sensor device is already known in which the torque transmitted to an axle is to be detected. The torque is determined by the torsion or the angle of rotation of the ends of the axle and a constant that depends on the material and geometry of the axle. Two magnets and one Hall sensor opposite each magnet are mounted on two disks that each rotate with the axle and are mechanically solidly coupled to the ends of the axle.
For instance, to detect the torque acting on a steering wheel axle of a motor vehicle while the steering wheel is rotating, very small angle changes in both directions of rotation of the steering wheel must be measured. Evaluating the changes in the field originating at the magnets therefore requires an extremely sensitive and also temperature-stable measurement device.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved sensor device of the above-described type, by which small angular position changes of mechanical parts that rotate relative to each other are measured with great sensitivity.
The sensor device for measuring angle changes of mechanical parts that rotate relative to each other includes only one magnet mounted on one part and at least one magnetoresistive sensor mounted on another part opposite to the sole magnet. The at least one magnetoresistive sensor includes means for generating an electrical output signal according to a direction of the magnetic field lines at the magnetoresistive sensor or sensors. The sole magnet and the at least one magnetoresistive sensor are mounted on the respective parts so that a magnetic-field sensitive layer of the at least one magnetoresistive sensor extends so as to face a magnetic pole of the sole magnet. The magnetic-field sensitive layer of the at least one magnetoresistive sensor extends tangentially to a rotation direction in which the parts rotate relative to each other so that the sensor device. Thus the output signal of the at least one magnetoresistive sensor varies in a sensitive manner to a tangential component of the magnetic field.
Because the magnetic field of the magnet extends in the direction toward the respectively opposed sensor, and the sensor is a magnetoresistive sensor, great sensitivity in field line detection is possible. The magnetoresistive sensor is disposed opposite one pole of the magnet in such a away that the magnetic-field-sensitive layer extends tangentially to the rotation direction of the parts whose relative angular position changes. This advantageously exploits the fact that in a tight space (for instance>1 mm) above the pole of the magnet, a major change in the direction of the field lines occurs.
The magnetoresistive sensors according to the invention are controlled linearly because of their pronounced sensitivity to a directional component (in this case tangential) of the field lines and thus make it possible to measure very small angle changes upon a rotation of the magnet or of the sensor.
A preferred embodiment of the invention is based on a sensor device for detecting the torque in an axle that is known per se from U.S. Pat. No. 5,501,110 cited above. Here, the magnet and the sensor are each mechanically coupled to axially different points of the axle and face one another in such a way that torsion of the axle can be detected as an angle change.
In an advantageous embodiment, the measurement device can be realized in that two sensors are disposed in the magnetic field of the magnet and are interconnected in such a way that their differential output without an angle change can be set to zero. The zero point is present if the rotating axle is unloaded. A relative rotation of the parts with the magnets and the sensors causes a difference in the electrical analog outputs of the two sensors, which can be output directly as torque by means of electronic signal processing.
The magnet can be constructed cylindrically with axial magnetization, and the magnetoresistive sensor is preferably an AMR sensor (AMR=anisotropic magnetoresistive), a GMR sensor (GMR=giant magnetoresistive), or a CMR sensor (CMR=colossal magnetoresistive).
REFERENCES:
patent: 4361805 (1982-11-01), Narimatsu et al.
patent: 4724710 (1988-02-01), Murty
patent: 5148106 (1992-09-01), Ozawa
patent: 5501110 (1996-03-01), Peilloud et al.
patent: 26 58 697 (1979-09-01), None
patent: 44 18 539 A1 (1995-11-01), None
patent: 196 47 420 A1 (1997-12-01), None
patent: 801966 (1958-09-01), None
patent: WO 97/08527 (1997-03-01), None
Dukart Anton
Herderich Hans-Juergen
Jost Franz
Marx Klaus
Ullmann Thomas
Noori Max
Robert & Bosch GmbH
Striker Michael J.
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