Abstract:
A measuring device for contactless detection of an angle of rotation is comprised of a supporting plate ( 14 ) made of soft magnetic material which is used as a rotor. In a plane in relation to the supporting plate ( 14 ), two segments ( 16, 17 ) are disposed, which are separated by means of a slot ( 21 ) and a spacer gap ( 22 ). The supporting plate ( 14 ) is fastened to an axle ( 11 ) whose extension ( 12 ) or the axle ( 11 ) itself is comprised of a magnetically conductive material. The extension ( 12 ) protrudes into one of the segments ( 16 ) of the stator. The axle ( 11 ), particularly its extension ( 12 ), the supporting element ( 14 ), and the segments ( 16, 17 ) control the magnetic flux of the permanent magnet ( 15 ) disposed on the supporting plate ( 14 ). Through the inclusion of the axle ( 11 ) into the magnetic flux, the measuring device is constructed in a relatively simple and space-saving manner.

Description:
BACKGROUND OF THE INVENTION 
     The invention is based on a measuring device for contactless detection of an angle of rotation. German Patent Disclosure Document 196 34 381.3 has disclosed a sensor which is disposed in three planes one above the other. The rotor constitutes the central plane, wherein it is comprised of the supporting plate for a permanent magnet. The supporting plate itself is comprised of a magnetically non-conductive material so that the magnetic flux travels via both the other planes, i.e. the stator, and is controlled with the aid of two spacers that are disposed between the two planes of the stator. The shaft or the extension of a shaft to which the rotor is fastened, has no influence on the magnetic flux. With this sensor, a relatively broad angular range can in fact be measured without a signal reversal, but it is relatively large in terms of the axial direction due to the construction in three parallel planes. 
     SUMMARY OF THE INVENTION 
     The measuring device according to the invention for contactless detection of an angle of rotation has the advantage over the prior art that the sensor is relatively small in the axial direction. It is constructed of only two planes. The supporting plate of the permanent magnet, which represents the rotor, is simultaneously also used to convey the magnetic flux. Furthermore, the shaft or the axle on which the rotor sits its included in the conveyance of the magnetic flux, which obviates the need for additional magnetic flux-conducting parts. Furthermore, this construction reduces the number of parts and the assembly cost connected with them. 
     Due to its simple construction, the sensor can be integrated into various systems with relatively low assembly cost, for example a throttle measuring device or a pedal module for a gas pedal transmitter, or can be used as an independent sensor in throttle valve transmitters or a vehicle body spring deflection device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are represented in the drawings and will be explained in detail in the subsequent description. 
     FIGS. 1 to  4  show different views of a first exemplary embodiment or sections through it. In this connection, 
     FIG. 1 is a longitudinal section in the view direction X according to FIG. 3, 
     FIG. 2 is a section B—B according to FIG. 4, 
     FIG. 3 is a top view in the view direction Y according to FIG. 1, and 
     FIG. 4 is a longitudinal section in the direction A—A according to FIG.  3 . 
     FIGS. 5 and 6 show the magnetic flux at an angular rotation of 0° or an induction of B=0, 
     FIGS. 7 and 8 show the corresponding magnetic flux at a maximal angular rotation or at an induction of B=max, 
     FIG. 9 shows the corresponding course of the induction B over the rotation angle a. 
     Other exemplary embodiments that represent the sensor being built into a throttle valve adjuster or a pedal transmitter are represented as longitudinal sections in FIGS. 10 and 11. 
     Other exemplary embodiments are shown in a top view in FIGS. 12 and 14 and in a longitudinal section in FIGS. 13 and 15. 
     The FIGS. 16 to  24  depict different modifications of the exemplary embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1 to  4 , a sensor is labeled  10 , which with the aid of an axle  11 , is connected to a component that is not shown, whose rotational movement is to be detected. An extension  12  is attached to the end face of the axle  11 , so that a shoulder  13  is produced, upon which a rotor formed as a supporting plate is centrally placed. The axle  11 , the extension  12 , and the supporting plate  14  can be produced as individual components or as a single component. An annular permanent magnet  15  is disposed on the supporting plate  14 , with as great a radial distance as possible from the center point, ice. from the attachment point of the axle  11 . The greater the distance is here, the better the resolution of the measurement signal. The permanent magnet  15  can be embodied as a section of a circle (circle segment) or as part of a circular ring. Its angular range is at least as great as the maximal rotation angle to be detected that belongs to the monitoring or component or the component to be measured. As can be seen from the representations in FIGS. 2 and 3, the angular range of the permanent magnet  15  in this exemplary embodiment is 180° so that a 180° rotation angle to be measured can be achieved. The permanent magnet  15  is furthermore polarized in the axial direction, i.e. perpendicular to the supporting plate  12 . The supporting plate  14  is comprised of magnetically conductive, in particular, soft magnetic material. According to the invention, the axle  11  and the extension  12  or at least the extension  12  is also comprised of magnetically conductive, in particular soft magnetic material. 
     A stator, which is comprised of two segments  16 ,  17  is disposed in a second plane above the permanent magnet  15 , parallel to the supporting plate  14  and spaced slightly apart from it. The segment  16  encloses the extension  12  with an arc  19 . In this exemplary embodiment, the arc  19  is embodied as a circular arc. However, a different contour is also conceivable. It is essential, however, that a magnetically conductive connection is possible between the extension  12  and the segment  16 . The gap  20  between the axle  11  and the arc  19  must therefore be embodied as small as possible. A continuous gap is formed between the two segments  16 ,  17  and in the exemplary embodiment according to FIGS. 1 to  4 , has two identically embodied outer sections  21  and a central spacer section  22  disposed in the vicinity of the arc  19 . With the spacer gap  22 , it is important that as little as possible magnetic flux of the magnetic field lines generated by the permanent magnet  15  can exist between the segments  16  and  17 , i.e. in this exemplary embodiment in the vicinity of the arc  19 . The spacer gap  22  can consequently be filled with air or another magnetically non-conductive material. If the spacer gap  22  is filled with air, then it must be embodied as larger in relation to the gap  21  in order to achieve this above-mentioned effect. Instead of air, a different magnetically non-conductive material can also be selected. A magnetic field sensitive element  25 , such as a field plate, a magnetic transistor, coils, a magneto-resistive element, or a Hall element is disposed approximately in the center of the gap  21 . It is important here that the magnetic field-sensitive component has as linear as possible a dependency of its output signal on the magnetic induction B. FIGS. 1 to  4  respectively show a measurement with the aid of a single magnetic field-sensitive element  25 , a Hall element. However, it would also be possible to dispose for example one element  25  in both gaps  21  in order to be able to carry out a so-called redundant measurement (backup measurement). It would also be conceivable to dispose two elements in one gap. If, as can be seen in FIG. 3, only one magnetic field-sensitive element  25  is disposed in one gap  21 , then the opposing gap  21  can also have the size of the spacer gap  22  and can consequently have the magnetically non-conductive function that the spacer gap  22  has. Naturally, it is also possible not only to symmetrically dispose the gap  21  used as the measurement gap, but also to dispose it asymmetrically or even at an angle. It is important here that the gap  21  be embodied as relatively small in relation to the spacer gap  22  in order to permit as uninterrupted as possible a flux of the magnetic lines through the magnetic field-sensitive element  25 . 
     FIG. 9 depicts the course of the characteristic curve of the magnetic induction B in the element  25 , e.g. a Hall element, over the rotational angle a of the axle  11 . It is clear that a rotational angle α of 0°, the induction B is likewise 0, whereas at the maximal rotational angle α, it also achieves the maximal induction value. In this exemplary embodiment, the maximal rotation angle is achieved at 180°. FIGS. 5 and 6 show the position of the sensor  10  at a rotational angle of 0°. It is clear that the magnetic flux travels from the permanent magnet  15  via the small gap, which serves the mobility of the rotor in relation to the stator, to the segment  16 , from there via the small bearing gap to the extension  12 , and from their via the supporting plate  14  back to the permanent magnet  15 . As is particularly clear from FIG. 6, the magnetic flux is controlled so that a rotation angle of 0°, it does not travel through the element  20  so that no magnetic induction B can occur in the element  25 . If the axle  11  and consequently the supporting plate  14  with the permanent magnet  15  is now rotated, then the magnetic flux traveling through the element  25  is increased and the linear and the linear measurement line depicted in FIG. 9 is produced. FIGS. 7 and 8 show the setting at the maximal rotation angle α. FIG. 7 is a view of FIG. 8 in the viewing direction A. In the position of the maximal rotation angle α, the entire magnetic flux of the permanent magnet  15  travels via the small gap into the segment  17 . From there, the magnetic flux flows through the one gap  21  into the segment  16  and on the opposite side, flows via the other gap  21  back through the bearing gap into the extension  12  and from there, via the supporting plate  14  to the permanent magnet  15 . It is particularly clear from FIG. 8 that when passing the gap  21  almost all of the magnetic flux is conveyed through the element  25  and as a result, a maximal possible magnetic induction B is produced in the element  25 . It is also clear from FIG. 8 that the spacer gap  22  produces a course of the magnetic lines almost completely through the gap  21  and consequently through the element  25 . As little magnetic flux as possible is permitted via the spacer gap  22 . 
     The exemplary embodiment according to FIG. 10 shows the installation of the above-described sensor in a throttle valve adjusting unit  30 . With the aid of this unit  30 , the rotation angle of a throttle valve is detected for a motor control. In this connection, the segments  16 ,  17  of the stator are disposed directly in the cover  31  of the throttle valve adjusting unit  30 . Since the cover  31  is comprised of plastic, the segments  16 ,  17  can be injection-molded into the cover  31 . However, it would also be possible to clip the two segments  16 ,  17  of the stator into the cover  31 . Naturally, there must be a gap  33 , however, which permits a magnetic flux from the permanent magnet  15  to the segments  16  and  17 . One or both of the elements  25  are in turn disposed in a gap  33 , which is not visible in FIG.  10 . The axle  11  in this connection is fastened directly to the shaft  32  of the throttle valve or represents an extension of this shaft  32 . The supporting plate  14  with the permanent magnet  15 , which plate is used as a rotor, is consequently fastened directly to the shaft  32  of the throttle valve. Without great changes, the sensor according to FIGS. 1 to  4  or  12  to  15  can be built into a throttle valve adjusting unit  30 . In this connection, the previously used potentiometer, for example, can be simply replaced. FIG. 11 depicts a pedal transmitter. In FIG. 11, the segments  16 ,  17  of the stator are disposed in the bottom  40  of the unit  30   a . The segments  16 ,  17  here can once again be injection-molded or clipped into the bottom  40 . The extension of the shaft  32  consequently protrudes through the stator, and the supporting plate  14  that is used as a rotor is fastened to the end of the axle  32 . Consequently, according to FIGS. 10 and 11, the sensor corresponding to the embodiments of FIGS. 1 to  4  or  12  to  15  can be adapted to the structural conditions of the throttle valve adjusting unit  30  or the pedal transmitter. 
     In the exemplary embodiment according to FIGS. 12 and 13, the supporting plate of the sensor is no longer a full disk. It is sufficient for the supporting plate  14   a  to be embodied as a segment that has an angular range which corresponds to the size of the permanent magnet  15 . FIG. 12, with reference to FIGS. 1 to  4 , shows a permanent magnet with an angular range of 180°. Consequently, the supporting plate  14   a  also has an angular range of approximately 180°. The outer contour of this supporting disk  14   a , which is embodied as a segment, can be embodied arbitrarily. So for example in FIGS. 14 and 15, the supporting segment  14   b  is embodied as a gear segment. As can be seen particularly in FIG. 15, the gear segment  45  is injection-molded onto the supporting disk  14   b , wherein the gear segment  45  also encompasses the permanent magnet  15 . With the aid of the gear segment, which is made of magnetically non-conductive material, a driving force can be simultaneously introduced into the supporting plate. This permits an integration into a drive device and consequently, a very compact construction. 
     In the exemplary embodiment according to FIGS. 16 to  19 , a recess  50  is embodied at each of the transitions from the gap  22  into the two gaps  21 . The recesses  50  in this connection represent an elongation of the gap  22 , which protrudes into the segment  16  of the stator. FIG. 18 depicts the recesses  50  as arc-shaped, but a different form is also conceivable. It is important here that the recesses  50  protrude at least 15° into the segment  16 . With an arc-shaped embodiment, the side edges of the recess  50  represent an elongation of the gap  22 , which is enclosed with a circular arc. The recesses  50  hinder the magnetic stray flux of the permanent magnet  15  to a relatively large degree. As result, the stray flux at the transition from the gap  22  to the two gaps  21  is minimized, which further improves the output signal in its linearity. As result of the recesses  50 , it is possible to reduce the size of the gap  22  used as a spacer gap in comparison to the exemplary embodiments above and consequently, to reduce the size of the sensor. In order to achieve an optimal use of the magnetic flux, the area of the segments  16  and  17 , which are disposed opposite one another in the vicinity of the two gaps  21 , should be virtually equal. Like the gap  22  in this exemplary embodiment or in the previous ones, the recesses  50  should be filled with air or, as a magnetically non-conductive spacer, should be filled with a corresponding material compound. It is important for the size ratio between the gap  21 , the gap  22 , and the recess  50  that the gap  22  and the recesses  50  are much larger in proportion than the two gaps  21  so that no magnetic flux of the permanent magnet  15  is possible via the gap  22  and the recesses  50  and consequently, this magnetic flux travels almost completely via the two gaps  21 . As shown in FIG.  18  and mentioned in the previous exemplary embodiments, it is possible that there is only one magnetic field-sensitive element  25  in one gap  21 . In this connection, it is conceivable to embody the diametrically opposing gap on the same order of magnitude as a gap  21  with the magnetic field-sensitive element  25 . However, it is also conceivable to embody this gap  21 , which is not filled with a magnetic field-sensitive element  25 , on the order of magnitude of the gap  22  and consequently to embody it as a spacer gap. As mentioned above, it can in this case have the order of magnitude of the gap  22  and/or can additionally be filled with magnetically non-conductive material or air. In the FIGS., the gap  21  with the magnetic field-sensitive element  25  is depicted as a gap that extends radially outward. However, it would also be conceivable for this measurement gap to be embodied as angled or asymmetrical. 
     In FIGS. 20 to  23 , the magnetic flux is now shown at the rotation angle positions α=0 degrees and α= the maximal rotation angle corresponding to the FIGS. 5 to  9 . It is clear from FIGS. 20 and 21 that as a result of the recesses  50 , the magnetic flux of the permanent magnet  15  into the inside of the segment  16  is also prevented so that at the angle position α=0 degrees, the induction B is likewise zero and is hardly tainted by any stray flux. However in FIGS. 22 and 23, the maximal induction value B=Max is also achieved at the maximal rotation angle α. As a result of the recesses  50 , a stray flux is also prevented here which would bypass the magnetic field-sensitive element  25 . 
     Consequently, virtually all of the magnetic flux is conveyed via the magnetic field-sensitive elements. FIG. 24 shows a modification of the rotor  14   a . Due to the geometry of the rotor  14   a , the linearity of the characteristic curve of the sensor over the measurement range of 140 degrees is significantly improved. The magnetic stray flux of the permanent magnet  15   a  is minimized and as a result, the zero point of the measurement curve of the sensor has a high degree of temperature stability. As is clear from FIG. 24, the rotor  14   a  represents a circular segment which in contrast to the rotor  14  of the previous exemplary embodiments, has an angle of &lt;180°. The rotor  14   a  in this connection must encompass the axle  11 . The circular section  60  of the rotor  14   a , which lies between the points C and B, has its center point in the center point M of the shaft  11 . Furthermore, a line S extends through the center point M. The rotor  14   a  is embodied as mirror-inverted in relation to this line S. This means that a connection of the point C to a point A, which lies on the line S, and a connection of the point B to this point A each have the same angle in relation to the line S. The point A his disposed on the side of the rotor  14   a  opposite from the circular arc shape  60 . In the vicinity of the points A, B, and C, the rotor  14   a  must have rounded edges. The magnitude of the angle of the rotor  14   a  depends on the magnet segment  15   a  that is used. The assurance must be made that the angular range of the rotor  14   a  is equal to or greater than that of the magnet used.