TECHNICAL FIELD

[0001] The present invention generally relates to rotational position sensors, and more particularly relates to a non-contact rotational position sensor system.

BACKGROUND

[0002] Position sensors are used in myriad environments, including automobile and various industry control environments. For example, many automobiles include a position sensor to sense various rotational positions of the transmission gear control shaft. Typically, the type of position sensor that is used for this application is a contact sensor. With this type of position sensor, signals representative of the position of the control shaft are generated when mechanical switch components engage and disengage.

[0003] Although contact sensors generally work well and are generally safe, these types of switches can suffer certain drawbacks. For example, the lifetime of the mechanical switch components can be shortened with repeated use. Contact sensors can be structurally complex, adding to their cost. Additionally, the electrical signals generated by contact sensors may not be sufficiently stable when a vehicle is experiencing vibration.

[0004] Hence, there is a need for a sensor that can sense the rotational position of an object, such as a transmission gear control shaft, and that alleviates one or more of the above-identified drawbacks. Namely, a sensor that exhibits suitable lifetime with repeated use and/or is relatively non-complex and inexpensive and/or exhibits sufficient signal generation stability when a vehicle is experiencing vibration. The present invention addresses one or more of these needs. BRIEF SUMMARY

[0005] In one embodiment, a sensor system is provided for sensing the rotational position of a rotating body that is configured to rotate between at least a first fixed position and a second fixed position, where the second fixed position is spaced radially from the first fixed position by a predetermined radial distance in a first rotational direction. The sensor system includes a magnet carrier, a first magnet, a second magnet, and a bipolar magnet. The magnet carrier is configured to mount on the rotating body and thereby rotate between the first fixed position and the second fixed position. The first magnet has a first magnetic pole and a second magnetic pole. The first magnet is coupled to the magnet carrier and has an inner surface and a curved outer surface, the first magnetic pole of the first magnet faces radially inward, the second magnetic pole of the first magnet faces radially outward, and the curved outer surface of the first magnet has a first arc length. The second magnet has the first magnetic pole and the second magnetic pole. The second magnet is coupled to the magnet carrier and is spaced radially apart from the first magnet. The second magnet has an inner surface and a curved outer surface, the first magnetic pole of the second magnet faces radially outward, the second magnetic pole of the second magnet faces radially inward, and the curved outer surface of the second magnet has a second arc length that is greater than the first arc length. The bipolar magnetic sensor is non-movably mounted at a location adjacent to the magnet carrier and is configured to switch between a first state and a second state in response to variations in magnetic field intensity and polarity at the location. The bipolar magnetic sensor is in the first state when the magnet carrier is in the first fixed position, and in the second state at least when the magnet carrier is in the second fixed position.

[0006] In another embodiment, a sensor system is provided for sensing the rotational position of a rotating body that is configured to rotate between a first fixed position, a second fixed position, and a third fixed position, where the second fixed position is spaced radially from the first fixed position by a predetermined radial distance in a first rotational direction, and the third fixed position is spaced radially from the first fixed position by the predetermined radial distance in a second rotational direction that is opposite the first rotational direction. The sensor system includes a magnet carrier, a first magnet, a second magnet, a third magnet, and a bipolar magnetic sensor. The magnet carrier is configured to mount on the rotating body and thereby rotate between the first fixed position, the second fixed position, and the third fixed position. The first magnet has a first magnetic pole and a second magnetic pole, is coupled to the magnet carrier, and has an inner surface and a curved outer surface. The first magnetic pole of the first magnet faces radially inward, the second magnetic pole of the first magnet faces radially outward, and the curved outer surface of the first magnet has a first arc length. The second magnet has the first magnetic pole and the second magnetic pole, is coupled to the magnet carrier, and is spaced radially apart from the first magnet. The second magnet has an inner surface and a curved outer surface, the first magnetic pole of the second magnet faces radially outward, the second magnetic pole of the second magnet faces radially inward, and the curved outer surface of the second magnet has a second arc length that is greater than the first arc length. The third magnet has the first magnetic pole and the second magnetic pole, is coupled to the magnet carrier, and is spaced radially apart from the first magnet. The third magnet has an inner surface and a curved outer surface, the first magnetic pole of the third magnet faces radially outward, the second magnetic pole of the third magnet faces radially inward, and the curved outer surface of the third magnet has the second arc length. The bipolar magnetic sensor is non-mo vably mounted at a location adjacent to the magnet carrier and is configured to switch between a first state and a second state in response to variations in magnetic field intensity and polarity at the location. The first magnet is radially disposed between the second and third magnets. The bipolar magnetic sensor is in the first state when the magnet carrier is in the first fixed position, and the bipolar magnetic sensor in the second state at least when the magnet carrier is in either the second fixed position or the third fixed position.

[0007] In yet another embodiment, a rotational position sensor system includes a control shaft, a magnet carrier, a first magnet, a second magnet, a third magnet, and a bipolar magnetic sensor. The control shaft is configured to rotate between a first fixed position, a second fixed position, and a third fixed position. The second fixed position is spaced radially from the first fixed position by a predetermined radial distance in a first rotational direction, and the third fixed position is spaced radially from the first fixed position by the predetermined radial distance in a second rotational direction that is opposite the first rotational direction. The magnet carrier is coupled to the control shaft to rotate therewith between the first fixed position and the second fixed position. The first magnet has a first magnetic pole and a second magnetic pole, is coupled to the magnet carrier, and has an inner surface and a curved outer surface. The first magnetic pole of the first magnet faces radially inward, the second magnetic pole of the first magnet faces radially outward, and the curved outer surface of the first magnet has a first arc length. The second magnet has the first magnetic pole and the second magnetic pole, is coupled to the magnet carrier, and is spaced radially apart from the first magnet. The second magnet has an inner surface and a curved outer surface, the first magnetic pole of the second magnet faces radially outward, the second magnetic pole of the second magnet faces radially inward, the curved outer surface of the second magnet has a second arc length that is greater than the first arc length. The third magnet has the first magnetic pole and the second magnetic pole, is coupled to the magnet carrier, and is spaced radially apart from the first magnet. The third magnet has an inner surface and a curved outer surface, the first magnetic pole of the third magnet faces radially outward, the second magnetic pole of the third magnet faces radially inward, and the curved outer surface of the third magnet has the second arc length. The bipolar magnetic sensor is non-mo vably mounted at a location adjacent to the magnet carrier and is configured to switch between a first state and a second state in response to variations in magnetic field intensity and polarity at the location. The first magnet is radially disposed between the second and third magnets, the bipolar magnetic sensor is in the first state when the magnet carrier is in the first fixed position, and the bipolar magnetic sensor in the second state at least when the magnet carrier is in either the second fixed position or the third fixed position.

[0008] Furthermore, other desirable features and characteristics of the rotational position sensor will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

[0010] FIG. 1 depicts a plan view of a portion of a non-contact rotational position sensor system configured to sense the rotational position of a rotating shaft;

[0011] FIGS. 2 and 3 depict top and plan views, respectively, of a magnet carrier and magnets that may be used to implement the rotational position sensor system of FIG. 1 ;

[0012] FIG. 4 depicts magnetic flux lines that exist when the magnetic carrier of the sensor system depicted in FIG. 1 is in a first position; [0013] FIG. 5 depicts magnetic flux lines that exist when the magnetic carrier of the sensor system depicted in FIG. 1 has been rotated in a first direction and is in a second fixed position; and

[0014] FIG. 6 simultaneously depicts a first graph that illustrates the output of a magnetic sensor versus the angle of rotation of the magnetic sensor system of FIG. 1 , and a second graph that illustrates magnetic field intensity at the location of the magnetic sensor versus the angle of rotation of the magnet carrier of the sensor system of FIG. 1.

DETAILED DESCRIPTION

[0015] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description.

[0016] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Thus, any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Moreover, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as "first," "second," "third," etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical. [0017] Furthermore, depending on the context, words such as "connect" or "coupled to" used in describing a relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other manner, through one or more additional elements. Moreover, two elements may simply contact each other.

[0018] Referring now to FIG. 1, a plan view of a portion of a non-contact rotational position sensor system 100 is depicted. The position sensor system 100 is configured to sense the rotational position of a control shaft 102, and includes a magnet carrier 104, a plurality of magnets 106 (only one visible in FIG. 1), and a bipolar magnetic sensor 108. The control shaft 102 is configured to rotate at least between a first fixed position, a second fixed position, and a third fixed position. The first fixed position may be, for example, equivalent to a neutral position of an automobile transmission, and the second and third positions may be equivalent to other automobile transmission gear positions such as, for example, reverse and drive. In any case, the second fixed position is spaced radially from the first fixed position by a predetermined radial distance in a first rotational direction 103, and the third fixed position is spaced radially from the first fixed position by the same predetermined radial distance but in a second rotational direction 105 that is opposite the first rotational direction.

[0019] The magnet carrier 104 is coupled to the control shaft 102, and thus rotates therewith between the first fixed position, the second fixed position, and the third fixed position. The magnet carrier 104 may be variously configured, but in the depicted embodiment, as shown more clearly in FIGS. 2 and 3, the magnet carrier 104 includes a main body 202, an engagement flange 204, and a magnet mounting structure 206. The main body 202 is generally cylindrical in cross section and has an inner surface 208 that defines an opening 212 that extends through the main body 202. As FIG. 1 depicts, the control shaft 102 extends completely through the opening 212. As FIG. 1 further depicts, the engagement flange 204 preferably engages an interfacing flange 1 12 that is formed on the control shaft 102. One or more engagement tabs 212 (only one depicted in FIG. 1) extend perpendicularly from the engagement flange 204 and extend through slots formed in the interfacing flange 1 12. [0020] The magnet mounting structure 206 extends from both the main body 202 and the engagement flange 204, and has a generally fan-shaped cross section. The magnet mounting structure 206 includes an outer surface 214 that has a plurality of magnet mounting slots 216 formed therein. The number, size, and spacing of the magnet mounting slots 216 may vary, but in the depicted embodiment, there are three magnet mounting slots 216 - a first magnet mounting slot 216-1 , a second magnet mounting slot 216-2, and a third magnet mounting slot 216-3. The size and spacing of the magnet mounting slots 216, as will be described further below, will depend upon, for example, the selected size of the magnets 106.

[0021] The magnets 106 are disposed, one each, in a different one of the magnet mounting slots 216. As with the magnet mounting slots 216, the number of magnets 106 may vary, but the depicted embodiment includes three magnets - a first magnet 106-1 , a second magnet 106-2, and a third magnet 106-3. The first magnet 106-1 is mounted within the first magnet mounting slot 216-1 , the second magnet 106-2 is mounted within the second magnet mounting slot 216-2, and the third magnet 106-3 is mounted within the third magnet mounting slot 216-3. The first magnet 106-1 is thus radially disposed between, and is equidistantly spaced radially from, the second and third magnets 106-2, 106-3.

[0022] Each magnet 106 has an inner surface and an outer surface. More specifically, the first magnet 106-1 has an inner surface 218 and a curved outer surface 222, the second magnet 106-2 has an inner surface 224 and a curved outer surface 226, and the third magnet 106-3 similarly has an inner surface 228 and a curved outer surface 232. The curved outer surface 222 of the first magnet 106-1 has a first arc length (ai), and the curved outer surfaces 226 and 232 of the second and third magnets 106-2 and 106-3, respectively, each have a second arc length (a ₂ ) that is greater than the first arc length ( _\ ). In the depicted embodiment, the inner surfaces 218, 224, 228 of each magnet 106 are also curved. It will be appreciated, however, that the inner surfaces could be variously shaped and configured. It will additionally be appreciated that the first and second arc lengths may vary, and that the radial distance between the first magnet 106-1 and the second and third magnets 106-2, 106- 3 may vary. It one particular embodiment, the first arc length is about 2.5 millimeters, the second arc length is about 4.5 millimeters, and the second and third magnets are each spaced radially apart from the first magnet by an arc length of about 1 millimeter. [0023] Each magnet 106 also has a first magnetic pole and a second magnetic pole. In the depicted embodiment, the first magnetic pole is magnetic north (N) and the second magnetic pole is magnetic south (S). It will be appreciated, however, that the poles could be oppositely arranged. In the depicted embodiment, the first magnet 106-1 is disposed within the first magnet mounting slot 216-1 such that its first magnetic pole faces radially inward and its second magnetic pole faces radially outward. Conversely, the second and third magnets 106-2, 106-3 are disposed within the second and third magnetic mounting slots 216-2, 216-3 such that their first magnetic poles each face radially outward and their second magnetic poles each face radially inward.

[0024] Referring once again to FIG. 1 , the bipolar magnetic sensor 108 is non-movably mounted at a location adjacent to the magnet carrier 104. The bipolar magnetic sensor 108 may be variously implemented, but in a particular embodiment the bipolar sensor 108 is implemented using a bipolar Hall-effect sensor. No matter the specific implementation, the bipolar magnetic sensor 108 is configured to switch between a first state and a second state in response to variations in both the magnetic field intensity and magnetic polarity at its mounting location. In this regard, with the depicted arrangement, the bipolar magnetic sensor 108 is disposed and configured to be in the first state when the magnet carrier 104 is in the first fixed position, and to be in the second state at least when the magnet carrier 104 is in either the second fixed position or the third fixed position.

[0025] The operation of the non-contact rotational position sensor system 100 may be even more readily understood with reference to FIGS. 4-6. In particular, FIG. 4 depicts magnetic flux lines that exist when the control shaft 102 and magnetic carrier 104 are in the above-mentioned first position, FIG. 5 depicts magnetic flux lines that exist when the control shaft 102 and magnetic carrier 104 have been rotated in the first direction 103 and are in the above-mentioned second fixed position, and FIG. 6 simultaneously depicts a first graph 602 that illustrates the output of the magnetic sensor 108 versus the angle of rotation

(0) of the magnet carrier 104, and a second graph 404 that illustrates the magnetic field intensity (B) at the location of the magnetic sensor 108 versus the angle of rotation (Θ) of the magnet carrier 104. As FIGS. 4 and 6 depict, when the control shaft 102 and magnet carrier

104 are in the first fixed position, the magnetic sensor 108 is in the first state (e.g., its output is non-zero or a relatively high value). If the control shaft 102 and magnet carrier 104 are rotated out of the first fixed position, in either the first rotational direction 103 or the second rotation direction 105, the magnetic sensor 108 remains in its first state for angles of rotation between - θι and +Q\ . However, as depicted in FIGS. 5 and 6, when the control shaft 102 and magnet carrier 104 are rotated to angles of rotation of + Θ] or - Θ] (which correspond to the second fixed position and the third fixed position, respectively) or beyond, the magnetic sensor 108 switches to the second state (e.g., its output is zero or a relatively low value).

[0026] It will be appreciated that the first state and the second state of the magnetic sensor 108, as described above, may vary. For example, in some embodiments the output of the magnetic sensor 108 may be zero or a relatively low value when it is in the first state, and non-zero or a relatively high value when it is in the second state. It will additionally be appreciated that the specific angles of rotation that correspond to the second and third fixed positions may vary, and that the size, dimensions, spacing, and relative polarities of then magnets 106, just to name a few variables, may be varied to achieve the desired result. Furthermore, the magnets 106 are dimensioned such that the rotational accuracy of the rotational position sensor system 100 is relatively insensitive to translational movements thereof along the rotational axis of the shaft 102.

[0027] While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.