Electricity: measuring and testing – Electrical speed measuring – Including speed analog electrical signal generator
Reexamination Certificate
2002-10-08
2003-11-18
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Electrical speed measuring
Including speed analog electrical signal generator
C324S207160
Reexamination Certificate
active
06650106
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the priority of German Patent Application, Serial No. 101 49 794.6, filed Oct. 9, 2001, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a device for measuring a motion of a moving body, and more particularly to a motion sensor capable of inductively measuring the velocity and acceleration of a moving body.
A motion sensor for inductively measuring the velocity and acceleration of a moving body is known, for example, from German Pat. No. DE 37 30 841 A1. A primary time-independent magnetic field that passes through a disk orthogonally to the direction of motion, is produced in a locally confined partial area of the disk near the edge of the rotating, electrically conducting disk that forms the moving body. For producing the primary field, two opposing permanent magnets are provided along an air gap through which the disk extends. These permanent magnets are also magnetically short-circuited on the sides facing away from the disk by a yoke made out of a magnetic material, for example iron, so as to form a closed magnetic circuit. The primary magnetic field of the permanent magnets induces in the moving disk locally electrical eddy currents which in turn induce a counteracting magnetic eddy current field. A Hall effect sensor or another magnetic field sensor, for example a magneto-resistive sensor, is provided on both sides of the gap for measuring the magnetic flux density produced by the eddy currents. The magnetic field sensor can determine the tangential velocity or the angular velocity of the disk. Each of the two magnetic field sensors is arranged in a gap of a corresponding flux collector ring made of magnetic material, for example iron, and also in the air gap between the two permanent magnets. Each of the flux connector rings defines a magnetic flux path in form of a loop which extends parallel to the disk or to the rotation plane of the disk and perpendicular to the primary field. Each of the flux connector rings has a linear segment which extends between the corresponding permanent magnets and the disk, wherein the gap with the magnetic field sensor is formed in the center of the segment, and a second U-shaped segment which is connected with the first straight segment and complements the first linear segment to form a closed flux path, with the U-shaped second segment projecting outwardly from the gap. The second segment of each of the two flux connector rings is surrounded outside the gap by a corresponding detector coil. These two detector coils measure the temporal variation of the flux density produced by the eddy currents and thereby provide a measurement signal for the temporal change of the tangential velocity or the rotation speed, and also for the acceleration or the rotational acceleration speed of the disk. Both the magnetic field sensors and the detector coils are oriented so as to measure the flux of the eddy current field which extends tangentially to the motion direction. According to DE 37 30 841 A1, both the magnetic field sensor and the induction coils are arranged closer to the moving body than the two permanent magnets and, on the other hand, as viewed in the motion direction, at the same height as the partial region in the moving body through which the primary magnetic field passes.
The device described in DE 37 30 841 A1 measures the tangential component of the measuring magnetic field in the air gap between the permanent magnets. However, since the tangential component can be accurately measured only at a relative large distance from the moving body, the permanent magnets in this prior-art device have to be arranged quite far from each other. As a result, the applied magnetic field becomes relatively small due to demagnetizing effects, resulting in a correspondingly small useful signal.
It would therefore be desirable and advantageous to provide an improved device for measuring a motion of a moving body to obviate prior art shortcomings.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a device for measuring a motion of an moving body (or: moved object) which is electrically conducting at least partially in a certain region includes magnetic field generating means (or: magnetic field sources) for producing a magnetic field (or: exciter field) which induces electric currents in the electrically conducting area of the moving body depending on the motion of the moving body, and at least one measuring device (or: detection device) for measuring a measuring magnetic field (or: measuring induction field) induced by the electric currents in the electrically conducting area of the moving body as a measure for at least one motion parameter of the moving body. The measuring device(s) measure(s) the measuring magnetic field at one location, where the field is at least approximately parallel to the motion direction. The magnetic field generating means are located closer to the moving body than the measuring device.
The term magnetic field or measuring magnetic field is used both for the traditional magnetic field—as used in the physical sciences—as well as for a magnetic induction field (or: the magnetic flux density) or a magnetic flux, or a combination thereof. The measurement or evaluation of the measuring magnetic field also includes measuring or evaluating its temporal change or another function of the measuring magnetic field. For measuring the moving body in the magnetic field, only the relative motion between the moving body and the magnetic field is important. Accordingly, the moving body can be stationary relative to a pre-determined reference system, in particular the earth surface or to a machine part, and the magnetic field can be moved relative to the reference system or the magnetic field can be stationary relative to the reference system or the moving body can be moved relative to the reference system. The motion of the moving body is generally arbitrary and can be a translation, for example a linear motion, or a rotation, as well as a combination of a translation and rotation.
The invention is based on the concept, that the tangential magnetic field of the electric currents induced into moving body during its motion in the applied magnetic field of the magnetic field generating means can be measured with one or several measuring devices, and that these measuring devices can be to placed at a greater distance from the moving body than the magnetic field generating means. The invention is based on the observation that the tangential measuring magnetic field is relatively homogeneous or uniform, so that the distance between the measuring device and the moving body can be varied over a wider range than when measuring the vertical measuring magnetic field, which produces only relatively small changes in the measurement signal. Accordingly, the device of the invention has a greater installation tolerance for the measuring device(s) and/or a greater tolerance with respect to measurement deviations or unevenness of the surface of the moving body. The invention is based on another observation that measuring the tangential measuring magnetic field at a greater distance than the distance of the magnetic field generating means for the moving body produces an improved useful signal.
According to an advantageous embodiment, at least one measuring device includes at least one induction coil for measuring the measuring magnetic field, which in general has a coil axis which is at least approximately perpendicular to the magnetic field of the magnetic field generating means and/or at least approximately parallel to a motion direction of the moving body.
For guiding the measuring magnetic field through the induction coil (s) or also as a carrier for the coil winding, each induction coil generally has its own magnetic flux conduction body or coil core. Moreover, at least one termination element can be arranged on the end faces of each induction coil not only for gu
Daalmans Gabriel
Finkler Roland
Feiereisen Henry M.
Patidar Jay
Siemens Aktiengesellschaft
Zaveri Subhash
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