Abstract:
A transmitter system for a Ferraris motion transmitter, includes a magnetic measuring arrangement including at least one magnetic field generator for generating a magnetic field and an electrically conductive measuring body, with the magnetic field generator and the measuring body movable relative to one another in operation. Coupled to the magnetic measuring arrangement is a magnetic field sensor for providing an output signal commensurate with a velocity or acceleration of the measuring body. At least one of the magnetic field generator and the magnetic field sensor includes at least two magnetic members interlocking one another in concentric relationship to the measuring body for guiding the magnetic field as a result of eddy currents forming during operation.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This application claims the priority of German Patent Application, Serial No. 101 56 782.0, filed Nov. 19, 2002, pursuant to 35 U.S.C. 119(a)(d), the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a transmitter system for a Ferraris motion transmitter.  
           [0003]    A typical transmitter system for a Ferraris motion transmitter includes one or more magnetic field generators which form together with an electrically conducting measuring body a magnetic measuring arrangement, whereby magnetic fields generators and the measuring body move relative to one another during operation. A magnetic field sensor is linked to the magnetic measuring arrangement to provide a speed-dependent or acceleration-dependent output signal. Such a transmitter system is disclosed, for example, in an article by A. Denne, H. Rausch and W, Freise, entitled “Aufnehmer zur Messung schnell veränderlicher Drehbeschleunigungen und Drehmomente” [ Measuring of dynamic angular acceleration and torque ], and published in Technisches Messen 48, 1981, Number 10, page 339 to 342. Hereby, the measuring body is implemented as a rotating bell-shaped rotor.  
           [0004]    German patent publication DE 37 30 841 A1 discloses a further transmitter system of this type in which the measuring body is implemented as disk.  
           [0005]    Provision of a transmitter system of simple and compact structure is desirous because of cost-saving aspects and small outer dimensions to satisfy an increasing demand for miniaturization and to allow their use in volume-critical devices. Conventional transmitter systems have a mechanical play between measuring body and other components of the transmitter system that may result in measuring errors. In conjunction with a rotating measuring body, the mechanical play may result in a misalignment between the symmetry axis of the measuring body and the shaft and/or the measuring body is not entirely rotation-symmetric. Other errors may be caused, for example, through eccentricity, wobbling or inhomogeneities of the measuring body. To address this problem, it was proposed to use at least two magnetic field sensors which are evenly spaced about a circumference. This, however, resulted in a more complicated structure of the transmitter system.  
           [0006]    It would therefore be desirable and advantageous to provide an improved transmitter system which obviates prior art shortcomings and is simple in structure while yet being reliable in operation and producing enhanced measuring quality.  
         SUMMARY OF THE INVENTION  
         [0007]    According to one aspect of the present invention, a transmitter system for a Ferraris motion transmitter includes a magnetic measuring arrangement having at least one magnetic field generator for generating a magnetic field and an electrically conducting measuring body, with the magnetic field generator and the measuring body movable relative to one another in operation, and a magnetic field sensor coupled to the magnetic measuring arrangement for providing an output signal commensurate with a velocity or acceleration of the measuring body, wherein at least one of the magnetic field generator and the magnetic field sensor includes at least two magnetic members interlocking one another in concentric relationship to the measuring body for guiding the magnetic field as a result of eddy currents forming during operation.  
           [0008]    The present invention resolves prior art problems by providing the transmitter system with at least two interlocking magnetic members in concentric relationship to the measuring body. In this way, the transmitter system according to the present invention can operate reliably by using only a single magnetic field sensor which, for example, may include a coil and partially surrounds the magnetic member, for detecting the magnetic field forming by the edge currents of the measuring body during operation. As a consequence, not only is the signal readout simplified but also the assembly of the transmitter system is significantly facilitated, because material can be saved and the assembly time of the transmitter system can be shortened. Moreover, it is possible that at least one magnet produces a magnetic field which can be guided by the at least two interlocking magnetic members in concentric relationship to the measuring body.  
           [0009]    According to another feature of the present invention, the magnetic field generator defines a magnetic field source direction in parallel relationship to the axis of the measuring body, with the magnetic field being guided by at least two exciter-side claw poles having magnetic field poles in concentric relationship to the measuring body and arranged such that the magnetic field poles of the claw poles alternatingly interlock one another. As a result, a plurality of exciter-side poles can be provided already with a single magnet. The magnet may hereby be configured as permanent magnet or as electromagnet.  
           [0010]    According to another feature of the present invention, the magnetic field sensor delivers an output signal in dependence on the magnetic field strength in the magnetic members as an end signal and intermediate signal. Suitably, the signal may be an electric signal and optical signal. Electrical signals outputted by the magnetic field sensor can easily be processed in an electronic processing or evaluation assembly. Optical signals can also be converted by signal converters into electrical signals and are advantageous because they can be tapped in a potential-free manner.  
           [0011]    According to another feature of the present invention, the magnetic field sensor may include at least one coil with at least one winding for partially surrounding at least one sensor-side claw-pole ring guiding the magnetic field during operation. In this way, the claw-pole ring can be used to detect the magnetic fields formed by the eddy currents during operation. Suitably, the at least one coil may be arranged in concentric relationship to the measuring body. As a result, the assembly of the transmitter system is significantly simplified, and, moreover, a sensor signal can already be evaluated which detects integrally the magnetic field of the transmitter system.  
           [0012]    According to another feature of the present invention, the magnetic field sensor may include at least one Hall element, or a magnetoresistive sensor, or a magnetooptic sensor.  
           [0013]    According to another embodiment of the present invention, the magnetic fields of at least two magnetic field generators pass through the measuring body, whereby the magnetic field generators are arranged on a radius in concentric relationship to the measuring body and alternatingly poled with different polarity. The concentric disposition of the magnetic field generators upon a radius in alternatingly poled manner allows detection of rotary motions of a rotating measuring body.  
           [0014]    According to another feature of the present invention, the magnetic field sensor may include at least one current-carrying coil with at least one winding for providing a magnetic field source, wherein alternating current or direct current can be impressed upon the coil. As a consequence, at least one electromagnet may be useable.  
           [0015]    According to another embodiment of the present invention, the transmitter system may include at least two magnetic field sensors, each including, e.g., a coil with at least one winding, wherein the useful fields, effected as a result of the relative movement of the measuring body, in the magnetic field sensors are oppositely directed, and wherein the output signals of the magnetic field sensors are subtracted by the at least two magnetic field sensors. In this way, the sensitivity is enhanced as the useful signals are added up.  
           [0016]    According to another feature of the present invention, there is provided a magnetic shielding for at least partly shielding components of the transmitter system. In this way, magnetic noise fields from the measuring system of the transmitter system can be eliminated. Of course, the magnetic shielding may also be realized by the housing of the transmitter system.  
           [0017]    A transmitter system according to the present invention results in significant cost savings as far as manufacture and assembly thereof are concerned. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0018]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:  
         [0019]    [0019]FIG. 1 is a perspective view, in exploded illustration, of a first embodiment of a Ferraris motion transmitter according to the present invention;  
         [0020]    [0020]FIG. 2 is a detailed perspective view of a magnetic field generator;  
         [0021]    [0021]FIG. 3 is a schematic partly sectional illustration of sensor coils and magnetic fields generators;  
         [0022]    [0022]FIG. 4 is a perspective view, in exploded illustration, of a second embodiment of a Ferraris motion transmitter according to the present invention;  
         [0023]    [0023]FIG. 5 is a side view of the assembled Ferraris motion transmitter of FIG. 4; and  
         [0024]    [0024]FIG. 5 a  is a top view of the assembled Ferraris motion transmitter of FIG. 4. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]    Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way.  
         [0026]    Turning now to the drawing, and in particular to FIG. 1, there is shown a perspective view, in exploded illustration, of a first embodiment of a transmitter system  100  according to the present invention in the form of a Ferraris motion transmitter. The transmitter system  100  includes a magnetic field sensor comprised of a coil  11  and magnetic members in the form of claw-pole rings, generally designated by reference characters  1 ,  2 , and a magnetic field generator  3 . The claw-pole rings  1 ,  2  are of an identical construction, and each includes a carrier  4  which has a plurality of sensor-side claw poles  5 . In the assembled state, the claw-pole rings  1 ,  2  are placed adjacent one another in superimposed disposition, with the claw poles  5  opposing and interlocking one another in parallel relationship to the main axis of the transmitter system  100 .  
         [0027]    The magnetic field generator  3  is placed inwardly of the claw-pole rings  1 ,  2  and has a magnetic north pole N and a magnetic south pole S. Magnetic members, generally designated by reference numerals  6 ,  7  and configured as claw-pole rings encircle in opposite disposition the magnetic field generator  3 . The magnetic members  6 ,  7  are of an identical construction, and each includes a disk-shaped base area  8  and a plurality of exciter-side claw poles  9  which extend from the base area  8  at a right angle in parallel relationship to the main axis of the transmitter system  100 . The magnetic field generator  3  has a cylindrical configuration, with the magnetic members  6 ,  7  respectively adjoining the circular end faces of the magnetic field generator  3  with their circular base areas  8 . Thus, in the assembled state of the motion transmitter, the exciter-side claw poles  9  encircle the magnetic field generator  3 .  
         [0028]    The magnetic field generator  3  produces a main magnetic field which has a magnetic field source direction generally parallel to the main axis of the transmitter system  100  and passes through the magnetic members  6 ,  7 .  
         [0029]    A measuring body  10 , whose velocity or acceleration is to be ascertained, is movable relative to the magnetic field generator  3  and its magnetic members  6 ,  7  and may be secured, for example, to a driven shaft (not shown). The measuring body  10  is made of electrically conductive material. Thus, as the measuring body  10  moves, the main magnetic field induces eddy currents in the conductive material of the measuring body  10 , which in turn generate magnetic fields. The eddy currents and thus the resultant magnetic fields are velocity-dependent and acceleration-dependent. The magnetic fields caused by the measuring body  10  are detected by the magnetic field sensor of the transmitter system  100  to output a respective signal. The magnetic fields are sensed and guided with proper polarity by the sensor-side claw poles  5 . Hereby, the number of sensor-side claw poles  5  matches the number of exciter-side claw poles  9 .  
         [0030]    The transmitter system  100  according to the present invention is simple in structure and compact. In the assembled state, the sensor coil  11  surrounds the claw poles  5  of the claw-pole rings  1 ,  2  about the main axis. The magnetic members  1 ,  2  of the magnetic field sensor encircle the coil  11  and contact one another at their confronting sides of the sensor-side carriers  4 . In this way, the magnetic circuit is completed at these areas substantially without air gap. The coil  11  encircles the magnetic field in the claw poles  5  of the magnetic members  1 ,  2  and thus can output a sensor signal representative of the magnetic field.  
         [0031]    Turning now to FIG. 2, there is shown an arrangement of magnetic field generators  3 , whereby the magnetic field generators  3  are oriented on a radius R in concentric relationship to the main axis of the transmitter system  100 . The magnetic field generators  3  are arranged on a base carrier  12  in a manner that their magnetic field poles alternate. The base carrier  12  has a hollow cylindrical shape without circular outer surfaces and is oriented perpendicular to the axis of the transmitter system  100 . The magnetic field generators  3  may be realized as permanent magnets or electromagnets.  
         [0032]    [0032]FIG. 3 shows a schematic partly sectional view of sensor coils  11  and magnetic field generators  3  of a transmitter system comprised of two motion transmitters in axial superimposed disposition, whereby each motion transmitter is configured in accordance with the illustration of FIG. 4. For sake of simplicity, FIG. 3 shows only one half of the transmitter system with respect to the main axis and only by way of the coils  11  and their pertaining magnetic field generators  3 . Disposed above and below a carrier  13  are the coils  11  with different sense of winding. The magnetic field generators  3  are positioned interiorly in concentric relationship to the coils  11 . The magnetic field source direction of the superimposed generators  3  is hereby in opposite direction. As a consequence of this construction, shown only partly in FIG. 3, magnetic noise signals are eliminated from the sensor signal by subtracting the individual signals of the coils  11 . Therefore, the resultant output signal of the magnetic field sensor is doubled and an interfering magnetic field is eliminated. An interfering magnetic field results in sensor signals of same magnitude but different sign in the respective coils  11 .  
         [0033]    [0033]FIG. 4 shows a perspective view, in exploded illustration, of a second embodiment of a transmitter system in the form of Ferraris motion transmitter according to the present invention, generally designated by reference numeral  200 . Parts corresponding with those in FIG. 1 will be identified by corresponding reference numerals followed by an “a”. In this embodiment, the exciter-side claw-pole rings  6   a ,  7   a  partly encircle the sensor-side claw-pole rings  1   a ,  2   a  with their claw poles  5   a . In contrast to the embodiment of FIG. 1, the coil  11   a  is positioned interiorly in concentric relationship to the claw poles  9   a  of the exciter-side claw-pole rings  6   a ,  7   a  and, at the same time, interiorly in concentric relationship to the claw poles  5   a  of the sensor-side claw-pole rings  1   a ,  2   a.    
         [0034]    The magnetic field generator  3   a  of the transmitter system  200  is positioned interiorly in concentric relationship to the sensor coil  11   a  and the sensor-side claw poles  5   a  and has a generally cylindrical configuration with circular base surface, with a cylindrical central bore  14  being formed in the magnetic field generator  3   a . The magnetic field of the magnetic field generator  3   a  is passed with proper polarity through the exciter-side magnetic members (claw-pole rings)  6   a ,  7   a  about the entire arrangement. The magnetic members  6   a ,  7   a  adjoin opposite base surfaces of the magnetic field generator  3   a  and encircle the entire transmitter system  200 . In the exemplified embodiment of FIG. 4, the magnetic members  6   a ,  7   a  have a substantially pot-shaped configuration, with the claw poles  9   a  extending like prongs in parallel relationship to the main axis of the transmitter system  200 . A measuring body, not shown in FIG. 47 moves in concentric relationship to the main axis of the transmitter system outside the exciter-side claw poles  9   a  and the sensor-side claw poles  5   a.    
         [0035]    [0035]FIGS. 5 and 5 a  show side and top views of the transmission system  200  of FIG. 4. Of course, the transmitter system  200  must contain much mechanical apparatus which does not appear in the foregoing Figures for the sake of simplicity, e.g. a housing and the measuring body. FIG. 5 shows the transmitter system  200  in a position generally perpendicular to the main axis direction. The exciter-side claw poles  9   a  encircle hereby with proper polarity the sensor coil  11   a  with pertaining claw poles  5   a . In the top view of FIG. 5 a , the transmitter system  200  is shown as viewed in parallel direction to the main axis. The magnetic member  6   a  can be seen here in particular, with the claw poles  9   a  radiating in a star-like manner and bent at their outer edge by 90° so as to be oriented in main axis orientation.  
         [0036]    Also the transmitter system  200  according to the present invention is simple in structure and compact. A multiplication of the pole number, which is desirable for reducing revolution-periodic noise signals as a result of eccentricity, wobbling or inhomogeneities in the measuring body, is easily possible. This is also desirable because smaller dimensions of the individual poles and thus smaller time constants and better dynamics can be realized. The respective claw poles can be formed through punching processes and subsequent bending to provide the final shape. The sensor exciter-side magnetic members  1 ,  2 ;  1   a ,  2   a  and the exciter-side magnetic members  6 ,  7 ;  6   a ,  7   a  may be made of ferromagnetic material.  
         [0037]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. For example, it is certainly possible to apply further measures to enhance the measuring capabilities of the transmitter system, e.g. measures commonly utilized in transformers (core lamination). The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.  
         [0038]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and their equivalents: