Abstract:
A sensor assembly having a pair of sensors and a pair of sensor targets. Each of the sensors is an eddy current sensor that defines X, Y and Z axes that are orthogonal to one another such that the X-axes are aligned to a movement axis along which a structure is to be moved. The sensor targets are coupled to one another for common movement and are formed of an electrically conductive material that is configured to interact with a respective one of the eddy current sensors to cause the sensors to produce sensor signals that each vary in a distinct manner with movement of the targets parallel to the movement axis. The targets are configured such that their coordinated movement in a direction parallel to the Z-axes as they are moved along the movement axis has no effect on the determined location of the structure. A method is also provided.

Description:
FIELD 
       [0001]    The present disclosure relates to a sensor assembly. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    There is need in the art for an inexpensive, reliable and accurate sensor to monitor the position of a component that is translated along a movement axis, particularly in the field of actuators for driveline components. In this regard, actuators for driveline components typically present an environment that is not friendly to conventional sensors due to large thermal extremes, the presence of lubricant, and potentially the presence of metallic particles that are suspended in the lubricant. Since these sensors must operate reliably over an extended period of time, there is a desire to avoid the use of magnets in the sensors (e.g., Hall-effect sensors), since there is a possibility that metallic particles could be attracted to the magnet of the sensor. 
       SUMMARY 
       [0004]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0005]    In one form, the present disclosure provides a sensor assembly for determining a location of a structure that is translated along a movement axis. The sensor assembly includes a sensor mount, first and second sensors, and first and second targets. The first sensor is coupled to the sensor mount and is an eddy current sensor that has a first X-axis, a first Y-axis and a first Z-axis that are orthogonal to one another. The first X-axis is disposed parallel to the movement axis. The first sensor includes a first coil that is wound helically around the first Z-axis. The second sensor is coupled to the sensor mount and is an eddy current sensor that has a second X-axis, a second Y-axis, and a second Z-axis that are orthogonal to one another. The second X-axis is parallel to the first X-axis. The second Z-axis is parallel to the first Z-axis. The second sensor includes a second coil that is wound helically around the second Z-axis. The first target is configured to be coupled to the structure for movement therewith. The first target is formed of an electrically conductive material and is configured to interact with the first sensor to produce a first sensor signal that has a first magnitude that varies proportionally with movement of the first target along the first X-axis. The second target is configured to be coupled to the structure for movement therewith. The second target is formed of an electrically conductive material and is configured to interact with the second sensor to produce a second sensor signal that has a second magnitude that varies proportionally with movement of the second target along the second X-axis. The first and second targets are configured so that coordinated movement of the first and second targets within predefined limits in a direction parallel to the first and second Z-axes as the structure is moved along the movement axis is detectable from the first and second sensor signals. 
         [0006]    In another form, the present disclosure provides a sensor assembly for determining a location of a structure that is translated along a movement axis. The sensor assembly includes a sensor mount, first and second sensors, first and second targets and a controller. The first sensor is coupled to the sensor mount and is an eddy current sensor that has a first X-axis, a first Y-axis and a first Z-axis that are orthogonal to one another. The first X-axis is disposed parallel to the movement axis. The first sensor includes a first coil that is wound helically around the first Z-axis. The second sensor is coupled to the sensor mount and is an eddy current sensor that has a second X-axis, a second Y-axis, and a second Z-axis that are orthogonal to one another. The second X-axis is parallel to the first X-axis. The second Z-axis is parallel to the first Z-axis. The second sensor includes a second coil that is wound helically around the second Z-axis. The first target is configured to be coupled to the structure for movement therewith. The first target is formed of an electrically conductive material and is configured to interact with the first sensor to produce a first sensor signal that has a first magnitude that varies in a first predetermined manner with movement of the first target along the first X-axis. The second target is configured to be coupled to the structure for movement therewith. The second target is formed of an electrically conductive material and is configured to interact with the second sensor to produce a second sensor signal that has a second magnitude that varies in a second predetermined manner with movement of the second target along the second X-axis. The controller receives the first and second sensor signals and responsively determines the location of the structure along the movement axis. The first and second targets are configured such that coordinated movement of the first and second targets in a direction parallel to the first and second Z-axes within predefined limits as the structure is moved along the movement axis has no effect on the location of the structure that is determined by the controller. 
         [0007]    In a further form, the present teachings provide a method that includes: providing a structure that is movable along a movement axis; coupling a sensor assembly to the structure, the sensor assembly comprising first and second eddy current sensors and first and second targets that are mounted to the structure for movement along the movement axis; sensing the first target with the first eddy current sensor and responsively generating a first sensor signal; sensing the second target with the second eddy current sensor and responsively generating a second sensor signal; and using the first and second sensor signals to determine a location of the structure along the movable axis in a manner that is insensitive to coordinated movement of the first and second targets in a first direction that is perpendicular to the movement axis. 
         [0008]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0009]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0010]      FIG. 1  is a schematic top plan view of a sensor assembly constructed in accordance with the teachings of the present disclosure; 
           [0011]      FIG. 2  is a schematic right side view of the sensor assembly of  FIG. 1 ; 
           [0012]      FIG. 2A  is a schematic illustration of the sensor assembly that depicts each of the eddy current sensors as including an RLC gate-oscillator circuit that generates a frequency output; 
           [0013]      FIG. 3  is a sectional, partly schematic view of the sensor assembly of  FIG. 1  integrated into a vehicle driveline component having a clutch; 
           [0014]      FIGS. 4 through 7  are views depicting alternately constructed portions of the sensor assembly of  FIG. 1 , the alternately constructed portions being first and second sensor targets; and 
           [0015]      FIG. 8  is a view similar to that of  FIG. 3  but depicting the sensor assembly constructed in accordance with the teachings of the present disclosure as employing first and second sensor targets that are configured in the manner depicted in  FIG. 6  and mounted to a synchronizer. 
       
    
    
       [0016]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0017]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0018]    With reference to  FIGS. 1 and 2 , a sensor assembly constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The sensor assembly  10  can include a sensor mount  12 , a first sensor portion  14 , a second sensor portion  16  and a controller  18 . The sensor mount  12  can be any type of structure, such as a circuit board, to which the first and second sensor portions  14  and  16  can be mounted. 
         [0019]    The first sensor portion  14  can include a first sensor  22  and a first target  24 , while the second sensor portion  16  can include a second sensor  26  and a second target  28 . Each of the first and second sensors  22  and  26  can include a coil  32  that is mounted to the sensor mount  12  and configured to generate a magnetic field  36  when activated (i.e., when receiving alternating current). Each of the coils  32  can be oriented such that it disposed along an associated Z-axis  40  that extends perpendicular from a surface  42  of the sensor mount  12  to which the coils  32  are mounted. The wire of each coil  32  can be wound helically about the associated Z-axis  40  of the coil such that the coils  32  have a generally annular shape. Alternately, each of the coils  32  is wound in a helical manner that is parallel to the associated Z-axis  40  and parallel to an axis that is perpendicular the associated Z-axis  40 . In the particular example provided, each of the coils  32  is wound helically about its Z-axis  40  in a manner that is elongated about its Y-axis  44  so that when viewed from a plane that includes its X-axis  46  and Y-axis  44 , the coils  32  are generally oval in shape. 
         [0020]    The first target  24  can be formed of a plate-like piece of an electrically conductive material that has opposite surfaces  50  and  52  that are oriented perpendicular to the Z-axis  40 . The first target  24  is configured to interact with the magnetic field  36  generated by the coil  32  of the first sensor  22 . More specifically, placement of the first target  24  into the magnetic field  36  generated by the coil  32  of the first sensor  22  can induce eddy currents  54  in the first target  24 . The eddy currents  54  induced in the first target  24  can create an opposing magnetic field  56  that can interact with the magnetic field  36  generated by the coil  32  of the first sensor  22 ; the first sensor  22  can output a first sensor signal that is responsive to the magnitude of the opposing magnetic field  56 . The first sensor  22  is configured so that the magnitude of the interaction between the magnetic field  36  and the opposing magnetic field  56  is dependent upon a distance between the first target  24  and the coil  32  of the first sensor  22  along the Z-axis  40 . The first target  24 , however, is also configured to also render the first sensor  22  sensitive to the placement of the first target  24  along the X-axis  46 . In this regard, the first target  24  can be shaped in a manner that varies the amount of the electrically conductive material in which the opposing magnetic field  56  is generated as a function of the placement of the first target  24  along the X-axis  46 . For example, the first target  24  can be shaped so that the output of the first sensor  22  is ratiometric when the first target  24  is moved only along the X-axis  46 . In the particular example provided, the first target  24  defines a generally V-shaped notch or aperture  60  that is formed through the material that forms the first target  24  and aligned such that the axis  62  of the V-shaped notch  60  is disposed in a plane that includes the Z-axis  40  and the X-axis  46 . 
         [0021]    The second target  28  can be formed of a plate-like piece of an electrically conductive material that has opposite surfaces  64  and  66  that are oriented perpendicular to the Z-axis  40 . The second target  28  is configured to interact with the magnetic field  36  generated by the coil  32  of the second sensor  26 . More specifically, placement of the second target  28  into the magnetic field  36  generated by the coil  32  of the second sensor  26  can induce eddy currents  70  in the second target  28 . The eddy currents  70  induced in the second target  28  can create an opposing magnetic field  72  that can interact with the magnetic field  36  generated by the coil  32  of the second sensor  26 ; the second sensor  26  can output a second sensor signal that is responsive to the magnitude of the opposing magnetic field  72 . The second sensor  26  is configured so that the magnitude of the interaction between the magnetic field  36  and the opposing magnetic field  72  is dependent upon a distance between the second target  28  and the coil  32  of the second sensor  26  along the Z-axis  40 . The second target  28 , however, is also configured to also render the second sensor  26  sensitive to the placement of the second target  28  along the X-axis  46 . In this regard, the second target  28  can be shaped in a manner that varies the amount of the electrically conductive material in which the opposing magnetic field  72  is generated as a function of the placement of the second target  28  along the X-axis  46 . For example, the second target  28  can be shaped so that the output of the second sensor  26  is ratiometric when the second target  28  is moved only along the X-axis  46 . In the particular example provided, the second target  28  defines a generally V-shaped notch or aperture  78  that is formed through the material that forms the second target  28  and aligned such that the axis  80  of the V-shaped notch  78  is disposed in a plane that includes the Z-axis  40  and the X-axis  46 . 
         [0022]    The first and second targets  24  and  28  can be fixedly coupled to one another for common movement. For example, the first and second targets  24  and  28  can be fixedly mounted to a structure  84  that is movable at least along a movement axis  86  that is parallel to the X-axes  46 . The first and second targets  24  and  28  can be aligned in coordinated manner relative to the first and second sensors  22  and  26 , respectively, such that the Z-axes  40  are parallel to one another, the X-axes  46  are parallel to one another and to the movement axis  86 , the Y-axes  44  are parallel one another, and the axes  62 ,  80  of the V-shaped notches  60 ,  78  are parallel to one another and aligned along the X-axes  46 . In the particular example provided, the structure  84  to which the first and second targets  24  and  28  are coupled is a piece of aluminum plate into which the first and second targets  24  and  28  are formed. It will be appreciated that the first and second targets  24  and  28  could be formed as discrete components that are mounted to another structure to reduce cost and/or weight as desired. Moreover, it will be appreciated that the first and second targets  24  and  28  could be offset from one another along the Z-axis  40  of the first sensor  22 , and/or that the first and second sensors  22  and  26  could be similarly offset from one another along the Z-axis  40  of the first sensor  22 . 
         [0023]    The controller  18  can be coupled to any desired structure, such as the sensor mount  12 , and can be configured to receive the first and second sensor signals and to responsively determine a position of the structure  84  along the movement axis  86 . 
         [0024]    The second target  28  can be configured to interact with second sensor  26  in a manner that is different from the manner in which the first target  24  is configured to interact with the first sensor  22  so that the manner in which the second sensor signal varies in response to movement of the structure  84  along the movement axis  86  is different from the manner in which the first sensor signal varies in response to movement of the structure  84  along the movement axis  86 . In the particular example provided, the V-shaped notch  78  of the second target  28  is oriented opposite to the V-shaped notch  60  of the first target  24  so that movement of the structure  84  along the movement axis  86  in a first direction is associated with enlargement of the width of the V-shaped notch  60  of the first target  24  along the Y-axis  44  of the first sensor  22 , and reduction of the width of the V-shaped notch  78  of the second target  28  along the Y-axis  44  of the second sensor  26 . 
         [0025]    The V-shaped notch  60  in the first target  24  renders the first sensor portion  14  an absolute position sensor for positions along the X-axis  46  within a predetermined range. Similarly, the V-shaped notch  78  in the second target  28  renders the second sensor portion  16  an absolute position sensor for positions along the X-axis  46  within the predetermined range. Moreover, if there is no movement of the first and second targets  24  and  28  along the Z-axis  40  relative to the coils  32 , the value of the output of one of the first and second sensors  22  and  26  can be determined based on the value of the output of the other one of the first and second sensors  22  and  26  (i.e., the value of the second sensor signal can be determined based on the value of the first sensor signal and vice versa). 
         [0026]    In situations where the first and second targets  24  and  28  move in a coordinated manner along the Z-axis  40 , the values of the first and second sensor signals will be higher or lower (relative to their values when there is no movement along the Z-axis  40 ) depending on whether the first and second targets  24  and  28  have moved toward or away from the coils  32 . As such, the values of the first and second sensor signals will not relate to one another in the expected manner (i.e., as though there is no movement along the Z-axis  40 ) but rather will include a common offset. The controller  18  can be configured to identify the existence of a common offset and to effectively remove the common offset from the values of the first and second sensor signals to thereby isolate the portion of the first and second sensor signals that relates to the absolute position of the structure  84  along the movement axis  86  from signal noise that relates to movement of the structure along the Z-axis  40 . 
         [0027]    As an example, suppose that the values (y1, y2) of the first and second sensor signals are related to the position (x) of the structure  84  along the movement axis  86  (within predefined limits) in a linear manner according to the formulas: 
         [0000]        y 1= m ( x )− b;  
 
         [0000]      and 
         [0000]        y 2= b−m ( x ); 
         [0000]    where (m) is a predefined slope and (b) is a predefined constant. In a situation where the structure  84  is moved only along the movement axis  86  and does not move along the Z-axis  40 , the values of y1 and y2 will sum to zero (i.e., the value of y2 is the additive inverse of y1). Accordingly, the controller  18  can average the values of y1 and y2 determine information relevant to the positioning of the structure  84  along the Z-axis  40 . For example, if the average is non-zero, the structure  84  has been positioned at a location along the Z-axis  40  that deviates from a predefined location. Additionally, the absolute value of the average is indicative of the magnitude by which the position of the structure  84  deviates along the Z-axis  40  from the predefined location, and the sign (positive or negative) of the average is indicative of the direction along the Z-axis  40  that the structure  84  is located relative to the predefined location. 
         [0028]    Alternatively, the location of the structure  84  along the movement axis  86  can be determined by dividing the value of one of the first and second sensor signals by the sum of the values of the first and second sensor signals (e.g., the value of the first sensor signal divided by the sum of the values of the first and second sensor signals). Because the first and second sensor portions  14  and  16  employ a dual sensor configuration with complementing outputs, the controller  18  can: a) determine the value of each of the first and second sensor signals, b) determine the sum of the values, c) determine a first ratio that is equal to the value of the first sensor signal to the sum of the values, d) determine a second ratio that is equal to the value of the second sensor signal to the sum of the values, and e) determine the location of the structure  84  along the movement axis  86  based on the first and second ratios. 
         [0029]    Construction of the sensor assembly  10  in this manner can be relatively inexpensive, eliminates the need for calibration of the sensor assembly  10 , requires relatively little space for the packaging of the sensor assembly  10 , and permits the axial location of the structure  84  to be determined along the movement axis  86  with accuracy that can be better than 0.5% regardless of changes in voltage, temperature or the presence of vibration. 
         [0030]    With reference to  FIG. 2A , each of the first and second sensors  22  and  26  can include an RLC gate-oscillator circuit that cooperates with the eddy current sensor to generate a frequency output that is dependent on the magnetic field produced by the coils  32  of the first and second targets  24  and  26 , respectively, and the opposing magnetic fields  56  and  72  ( FIG. 2 ). 
         [0031]    In  FIG. 3 , the sensor assembly  10  can be employed to sense a position of a clutch fork  100  that is moved by a linear actuator  102  along a movement axis  86 . The clutch fork  100  is engaged to a synchronizer  104  in a conventional manner and is employed for translating the synchronizer  104  into and out of meshing engagement with a plurality of first coupling teeth  108  that are coupled to a driven gear  110  for common rotation. Those of skill in the art will appreciate that the structure  84  is the clutch fork  100  and that the first and second targets  24  and  28  ( FIG. 1 ) are mounted directly to (or alternatively formed in) the clutch fork  100 . The linear actuator  102  can be any type of device that is configured to translate the clutch fork  100  along the movement axis  86 . In the particular example provided, the linear actuator  102  is a electromagnetically operated solenoid, but those of skill in the art will appreciate that other types of linear motors, including fluid-powered cylinders, could be employed in the alternative. 
         [0032]    While the first and second targets  24  and  28  ( FIG. 1 ) have been described as comprising V-shaped notches  60 ,  78  ( FIG. 1 ), those of skill in the art will appreciate from this disclosure that the first and second targets  24  and  28  ( FIG. 1 ) could be shaped differently. For example, the first and second targets could be shaped as tapered surfaces as shown in  FIGS. 4 through 7 . In  FIG. 4 , the first and second targets  24   a  and  28   a  comprise sensing surfaces  120  and  122 , respectively, that taper along the Z-axes  40  in a ratiometric manner. In  FIGS. 5 through 7 , the first and second targets  24   b  and  28   b  comprise frusto-conical sensing surfaces  120   b  and  122   b , respectively, that taper in a radial direction. Configuration in this latter manner may be particularly suitable for situations in which the structure  84  is also rotatable about the movement axis  86  and the first and second targets  24   b  and  28   b  are coupled to the structure  84  for rotation and axial movement therewith. 
         [0033]    In  FIG. 8 , the sensor assembly  10   b  can be employed to sense a position of a rotating synchronizer  104  that is moved by a clutch fork  100  and a linear actuator  102 . The clutch fork  100  is engaged to a synchronizer  104  in a conventional manner and is employed for translating the synchronizer  104  into and out of engagement with a plurality of first coupling teeth  108  that are coupled to a driven gear  110  for common rotation. Those of skill in the art will appreciate that the structure  84  is the synchronizer  104  and that the first and second targets  24   b  and  28   b  are formed on a portion of the synchronizer  104  that is disposed on a side opposite the first coupling teeth  108 . 
         [0034]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.