Abstract:
A rotary position sensor apparatus includes a magnet having a surface and a plurality of Hall components placed within the surface of the magnet. The Hall components are located on a neutral axis of the magnet thereby forming a rotary position sensor apparatus having an enhanced linearity, a reduced calibration time and a compact size. A printed circuit board (PCB) can also be provided and the Hall components mounted to the PCB. The magnet preferably possesses a rectangular shape, but other shapes may be implemented depending upon design considerations.

Description:
TECHNICAL FIELD  
       [0001]     Embodiments are generally related to sensor systems and methods. Embodiments are also related to magnetic sensing systems and devices. Embodiments are additionally related to Hall Effect devices and rotary position sensors.  
       BACKGROUND  
       [0002]     Magnetic sensing devices have many applications, including navigation, position sensing, current sensing, vehicle detection, and rotational displacement. There are many types of magnetic sensors, but essentially they all provide at least one output signal that represents the magnetic field sensed by the device. The Earth, magnets, and electrical currents can all generate magnetic fields. The sensor may be able to detect the presence, the strength, and/or the direction of the magnetic field. The strength of the magnetic field may be represented by a magnitude and a polarity (positive or negative). The direction of the magnetic field may be described by its angular position with respect to the sensor. One of the benefits of using magnetic sensors is that the output of the sensor is generated without the use of contacts. This is a benefit because over time contacts can degrade and cause system failures.  
         [0003]     A Hall sensor is a type of magnetic sensor that uses the Hall Effect to detect a magnetic field. The Hall Effect occurs when a current-carrying conductor is placed into a magnetic field. A voltage is generated perpendicular to both the current and the field. The voltage is proportional to the strength of the magnetic field to which it is exposed. The current-carrying conductor is called a Hall element and it is typically composed of a semiconductor material.  
         [0004]     One of the first practical applications of the Hall Effect was as a microwave power sensor in the 1950s. With the later development of the semiconductor industry and its increased ability for mass production, it became feasible to use Hall Effect components in high volume products. In 1968, Honeywell&#39;s MICRO SWITCH division produced a solid-state keyboard using the Hall Effect. The Hall Effect sensing element and its associated electronic circuit are often combined in a single integrated circuit.  
         [0005]     In its simplest form, a Hall element can be constructed from a thin sheet of conductive material with output connections perpendicular to the direction of electrical current flow. When subjected to a magnetic field, the Hall Effect element responds with an output voltage that is proportional to the magnetic field strength. The combination of a Hall Effect element in association with its associated signal conditioning and amplifying electronics is sometimes called a Hall Effect transducer. Such Hall elements are typically implemented in the context of a Hall component or device such as a Hall chip.  
       BRIEF SUMMARY  
       [0006]     The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed can be gained by taking the entire specification, claims, drawings, and abstract as a whole.  
         [0007]     It is, therefore, one aspect of the present invention to provide for an improved rotary position sensor apparatus.  
         [0008]     It is yet another aspect of the present invention to provide for a rotary position sensor apparatus based on the integration of one or more Hall components and a magnet.  
         [0009]     It is a further aspect of the present invention to provide a rotary position sensor apparatus with a rectangular magnet and one or more Hall sensors placed within the surface of the magnet.  
         [0010]     The aforementioned aspects of the invention and other objectives and advantages can now be achieved as described herein. A rotary position sensor apparatus is disclosed, which includes a magnet having a surface and a plurality of Hall components placed within the surface of the magnet. The Hall components are located on a neutral axis of the magnet thereby forming a rotary position sensor apparatus having an enhanced linearity, a reduced calibration time and a compact size. A printed circuit board (PCB) can also be provided and the Hall components mounted to the PCB. The magnet preferably possesses a rectangular shape, but other shapes may be implemented depending upon design considerations.  
         [0011]     The rotary sensor apparatus can thus be implemented based on a rectangular magnet and one or more Hall chips placed within the magnet surface. The Hall chips can be placed exactly on the neutral axis of the magnet leaving sufficient air gap above the magnet. The Hall chips are mounted on a PCB which is fixed firmly in a stationary location of the sensor apparatus. The rectangular magnet can be press fitted in a rotary part of the sensor apparatus revolved over the Hall chips. An extended linearity can be provided as the chip is placed within the magnet surface. Additionally, a zero calibration time results when the magnet is rectangular in shape. Also, a dual analog output can be generated by placing the chips equidistant from the geometric center of magnet. Finally, a compact size can be achieved with less undesirable effects due to the presence of external magnetic fields, because the Hall chips are placed within the magnet surface.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the detailed description, serve to explain the principles of the disclosed embodiments.  
         [0013]      FIG. 1  illustrates an exploded view of a rotary position sensor apparatus, which can be implemented in accordance with a preferred embodiment;  
         [0014]      FIG. 2  illustrates a side sectional view of the rotary position sensor apparatus depicted in  FIG. 1  in accordance with a preferred embodiment;  
         [0015]      FIG. 3  illustrates a top view of the rotary position sensor apparatus depicted in  FIGS. 1-2  in accordance with a preferred embodiment;  
         [0016]      FIG. 4  illustrates a bottom view of the rotary position sensor apparatus depicted in  FIGS. 1-2  in accordance with a preferred embodiment;  
         [0017]      FIGS. 5A and 5B  illustrates a flow chart of operations depicting logical operational steps, which may be processed for assembling the rotary position sensor apparatus depicted in  FIGS. 1-4  in accordance with a preferred embodiment;  
         [0018]      FIG. 6  illustrates a diagram of a prior art magnet configuration;  
         [0019]      FIG. 7  illustrates a graph depicting a change B z  smoothed as a function of a radial angle in accordance with the prior art magnet configuration depicted in  FIG. 6 ;  
         [0020]      FIG. 8  illustrates a diagram of a proposed magnet configuration set up for avoiding alignment problems;  
         [0021]      FIG. 9  illustrates a graph depicting a change B z  smoothed as a function of a radial angle in accordance with the configuration depicted in  FIG. 8 ;  
         [0022]      FIG. 10  illustrates a diagram of an improved magnet configuration, which can be implemented in accordance with a preferred embodiment; and  
         [0023]      FIG. 11  illustrates a graph depicting a change B z  smoothed as a function of a radial angle in accordance with a preferred embodiment depicted in  FIG. 10 .  
     
    
     DETAILED DESCRIPTION  
       [0024]     The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope of the invention.  
         [0025]      FIG. 1  illustrates an exploded view of a rotary position sensor apparatus  100 , which can be implemented in accordance with a preferred embodiment. The apparatus  100  generally includes a magnet  110 , which is surrounded by a gasket  112  and located on a printed circuit board (PCB)  114 . A housing  120  is provided, which maintains an EMI shield  118  below the PCB  114 . A connector  116  permits the EMI shield  118  and the PCB  114  to be attached to the housing  120 , thereby supporting the magnet  110 . A rotor  108  surrounds the magnet  110 . The rotor  108  is in turn supported by a torsion spring  106  and a sealing ring  104 . A cover or cap  102  can be provided for maintaining the sealing ring  104 , the torsion spring  106  and the rotor within housing  120 .  
         [0026]      FIG. 2  illustrates a side-sectional view of the rotary position sensor apparatus  100  depicted in  FIG. 1  in accordance with a preferred embodiment. Note that in  FIGS. 1-2 , identical or similar parts or elements are generally indicated by identical reference numerals. Thus, in addition to the components depicted in  FIG. 1 , the side-sectional view of apparatus  100  illustrated in  FIG. 2  further illustrates terminals  202  disposed within housing  120 .  
         [0027]      FIG. 3  illustrates a top view of the rotary position sensor apparatus  100  depicted in  FIGS. 1-2  in accordance with a preferred embodiment.  FIG. 4  illustrates a bottom view of the rotary position sensor apparatus  100  depicted in  FIGS. 1-2  in accordance with a preferred embodiment. In  FIGS. 1-4 , identical or similar parts or elements are generally indicated by identical reference numerals.  
         [0028]      FIGS. 5A-5B  illustrates a flow chart of operations depicting logical operational steps, which may be processed for assembling the rotary position sensor apparatus depicted in  FIGS. 1-4  in accordance with a preferred embodiment. The method is initially depicted in  FIG. 5A  and continues as depicted in  FIG. 5B . The assembly process can be initiated as indicated at block  502 . Several operational paths can be performed simultaneously. The operations depicted at blocks  504 ,  506 , and  508  can be implemented, while the operations illustrated at blocks  510 ,  512   514 ,  516  can be processed. Similarly, the operation described at block  511  can also be processed and so on. As indicated at block  510  the rotor  108  can be inserted onto a fixture. Next, as depicted at block  510 , the magnet  110  can be inserted onto the rotor  108 . A check alignment test can then be performed as depicted at block  514 . If the test fails then the components are rejected as indicated at block  516 . If the test succeeds, however, then the operation continues.  
         [0029]     The operation illustrated at block  504  involves inserting the EMI shield  118  into the housing  120 . Thereafter, as depicted at block  506 , the PCB  114  can be inserted with the connector  116  into the housing  120 . Next, as illustrated at block  508 , the gasket  112  can be inserted into the housing  120 . Following processing of the operations described at blocks  514  and/or  508 , the operation depicted at block  58  can be processed in which the rotor  108  is inserted into the housing  120 . Next, as illustrated at block  520 , the torsion spring  106  can be inserted into the rotor  108  and housing  120  (i.e., housing assembly). Thereafter, as depicted at block  521 , a test can be performed to detect the assembled components. If the test fails, then the operation depicted at block  523  is processed. That is, the faulty component is replaced. If, however, the test depicted at block  521  is successful, then the cover  102  is placed on the housing  120  as described at block  524 . Note that the operation depicted at block  524  can also be processed following processing of the operation illustrated at block  511 . Following processing of the operation depicted at block  524 , the housing  120  can be ultrasonically welded to the cover  102 . A functional test can then be performed as indicated at block  528 . If the test fails, then the entire device is rejected. If, however, the test is successful then the resulting assembled apparatus  100  is deemed fit, as indicated at block  530 .  
         [0030]      FIG. 6  illustrates a diagram of a prior art magnet configuration  600 . A magnet  602  of the configuration  600  is generally circular In shape. Two Hall components (e.g., Hall chips)  604 ,  606  are located above the magnet  602  opposite one another. Note that as utilized herein the term “Hall” can be utilized interchangeably with the term “Hall Effect.” Hall components  604 ,  606  thus constitute Hall Effect devices or components (e.g., Hall Effect sensor). The linearity error for such a configuration is approximately 1.45% with offsets of 4.945 mm in X and 1.000 mm in Z. The diameter of the circular magnet can be, for example, 8.89 mm in “X” length with a 2.54 mm thickness. Arrow  608  depicted in  FIG. 6  generally indicates the rotation of magnet  602 .  FIG. 7  illustrates a graph  700  depicting a change B z  smoothed as a function of a radial angle in accordance with the prior art magnet configuration  600  depicted in  FIG. 6 . Graph  700  is thus associated with the configuration  600  Graph  700  indicates a region of interest  702  generally in an  80  degree range with respect to a plotted data curve  704 .  
         [0031]      FIG. 8  illustrates a diagram of a proposed magnet configuration  800  setup to avoid alignment problems. The configuration  800  can be set up with a magnet  802  having a generally rectangular shape with respect to Hall components  804  and  806 . Suggested parameters for magnet  802  are, for example, 10×12×2.54 mm. The rectangular shape of magnet  802  with respect to Hall Effect components  804  and  806  tends to avoid alignment problems. Arrow  808  generally indicates the rotation of configuration  800 .  
         [0032]      FIG. 9  illustrates a graph  900  depicting a change B z  smoothed as a function of a radial angle in accordance with the configuration  800  depicted in  FIG. 8 . A region of interest  904  is indicated in graph  900  with respect to a plotted curve  904 . The data plotted in graph  900  is generally associated with the magnet configuration  800  depicted in  FIG. 9 . Because the region of interest  904  indicated in graph  900  is not acceptable, the configuration  800  is also not acceptable for rotary sensing purposes.  
         [0033]      FIG. 10  illustrates a diagram of an improved magnet configuration  1000 , which can be implemented in accordance with a preferred embodiment. Note that in  FIGS. 8 and 10 , identical or similar parts or elements are generally indicated by identical reference numerals. In configuration  1000 , the positions of Hall chips or Hall components  804  and  806  are modified with the same magnet  802 . The Hall components  804 ,  806  are thus placed within the surface of magnet  802 . The Hall components  804 ,  806  are located on a neutral axis of magnet  802 , and forming and/or adapted for use with the rotary position sensor apparatus  100  discussed earlier. The resulting configuration  1000  for the rotary position sensor apparatus  100  provides an enhanced linearity, a reduced calibration time and a compact size.  
         [0034]      FIG. 11  illustrates a graph  1100  depicting a change B z  smoothed as a function of a radial angle in accordance with preferred alternative embodiment depicted in  FIG. 10 . Graph  1100  generally includes a region of interest  1102  with respect to a plotted data curve  1104 . Graph  1100  indicates the linearity error can be reduced to 0.30 by moving the chips  804 ,  806  closer within the magnet  802  boundary, thereby reducing space requirements. Suggested parameters for magnet  802  are, for example, 10×12×2.54 mm.  
         [0035]     The rotary sensor apparatus  100  described earlier can thus be implemented based on the use of the rectangular magnet  802  and one or more Hall chips  804 ,  806  placed within the surface of the magnet  802 . The Hall chips  804 ,  806  can be placed exactly on the neutral axis of the magnet  802  leaving a sufficient air gap above the magnet  802 . The Hall chips  804 ,  806  can be mounted on the PCB  114 , which is fixed firmly in a stationary location of the overall sensor apparatus  100 . The rectangular magnet  802  can be press fitted in a rotary part of the sensor apparatus revolved over the Hall chips  804 ,  806 .  
         [0036]     An extended linearity can be provided as the chips  804 ,  806  are placed within the surface of magnet  802 . A zero calibration time results because the magnet  802  is rectangular in shape. Also, a dual analog output can be generated by placing the chips  804 ,  806  equidistant from the geometric center of the magnet  802 . Finally, a compact size can be achieved with less undesirable effects due to the presence of external magnetic fields, because the Hall chips  804 ,  806  are placed within the magnet  802  surface. In general, the configuration  1000  depicted in  FIG. 10  can be implemented in place of magnet  110  depicted in  FIG. 1  and can be utilized for a number of rotary sensing applications, such as, for example, non-contact rotary position sensing, throttle position devices, pedal accelerators, door position detection and steering position devices.  
         [0037]     It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.