Abstract:
An inductive vehicle seat position sensor assembly determines a linear vehicle seat position and has a circuit board member. First and second transmitter coils are proximate to a periphery of the circuit board member and radiate an out of phase magnetic field in response to an alternating current input. First and second receiver coils are offset relative to one another. The first and second transmitter coils and the first and second receiver coils span along the circuit board member. A loop coil member is provided for relative motion to the circuit board member. The first and second receiver coils generate a voltage with phase information corresponding to a position of the loop coil member relative to the circuit board member. A signal conversion unit produces a seat position output corresponding to the vehicle seat position based on the voltage with phase information of the first and second receiver coils.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    Multiple embodiments relate to position sensor assemblies for vehicle seats. 
         [0003]    2. Background Art 
         [0004]    Currently, vehicle seat position sensors are utilized to determine seat position along a track of the vehicle seat. The vehicle seat position sensors are employed as an input to a restraint control module as a part of a safety system deployment strategy for front seat occupants. Typically, vehicle seat position sensors have a limited capability to only detect two distinct fore/aft zones (near and far) as needed by current safety system strategies. These vehicle seat position sensors function as switches and do not provide higher resolution seat linear position information. Often the vehicle seat position sensors are based upon the Hall effect/magnetic sensing. Switches in the vehicle seat position sensors indicate that an occupant is sitting too close to a safety system upon deployment, such as an airbag and help optimize airbag deployment for this condition. 
       SUMMARY 
       [0005]    In one embodiment, an inductive vehicle seat position sensor assembly to determine a linear vehicle seat position is provided with a circuit board member. First and second transmitter coils are each arranged proximate to a periphery of the circuit board member and radiate an out of phase magnetic field in response to an alternating current input. The first and second transmitter coils each span a length along the circuit board member. First and second receiver coils have a waveform and are offset relative to one another within the first and second transmitter coils. The first and second receiver coils each span the length along the circuit board member. A loop coil member is provided for relative motion to the circuit board member along the length of the circuit board member to interact with the first and second transmitter coils and the first and second receiver coils via inductive coupling. In response to the loop coil member positioned over the transmitter and receiver coils, each of the first and second receiver coils generate a voltage with phase information corresponding to a position of the loop coil member relative to the circuit board member. A signal conversion unit produces a seat position output corresponding to the vehicle seat position based on the unique voltage/phase of each of the first and second receiver coils. 
         [0006]    In another embodiment, an inductive vehicle seat position sensor system has an inductive sensor assembly to determine a vehicle seat position. A circuit board member is provided. First and second transmitter coils are each arranged proximate to a periphery of the circuit board member and radiate an out of phase magnetic field in response to an alternating current input. The first and second transmitter coils each span a length along the circuit board member. First and second receiver coils have a waveform and are offset relative to one another within the first and second transmitter coils. The first and second receiver coils each span the length along the circuit board member. A loop coil member is provided for relative motion to the circuit board member along the length of the circuit board member for interacting with the first and second transmitter coils and the first and second receiver coils via inductive coupling. In response to the loop coil member positioned over the transmitter and receiver coils, each of the first and second receiver coils generates a voltage with phase information. A signal conversion unit produces a seat position output corresponding to the vehicle seat position based on the unique voltage/phase of each of the first and second receiver coils. A restraint control module communicates with the inductive sensor assembly to receive the seat position output and communicates with at least one auxiliary passenger safety device to provide an input. 
         [0007]    In another embodiment, a vehicle seat frame assembly is provided. A vehicle seat frame has a pair of generally parallel lateral frame members that are slidably engageable with a pair of seat tracks adapted to be mounted to a vehicle floor. An inductive sensor assembly determines a position of the lateral frame members relative to the seat tracks. A restraint control module communicates with the inductive sensor assembly and communicates with at least one auxiliary passenger safety device to provide an input. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic representation of a vehicle seat frame equipped with an inductive vehicle seat position sensor assembly; 
           [0009]      FIG. 2  is a schematic overview of a vehicle safety system with an inductive vehicle seat position sensor assembly according to the present invention; 
           [0010]      FIG. 3  is a top view of an embodiment of an inductive vehicle seat position sensor assembly; 
           [0011]      FIG. 4  is a side view of the inductive vehicle seat position sensor assembly of  FIG. 3  with an attached signal conversion unit; and 
           [0012]      FIG. 5  is a graph comparing seat track position to sensor output voltage. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0013]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0014]    With reference to  FIG. 1 , a detailed top view of a vehicle seat is illustrated and generally referenced by numeral  10 . For illustrative purposes, trim and cushioning have been removed. While only a passenger seat  10  is depicted, a driver seat is also contemplated within the scope of the embodiments disclosed. 
         [0015]    As illustrated, the vehicle seat  10  has lateral frame members  12 ,  14 , respectively that are spaced apart by cross members  16 ,  18 , respectively. The vehicle seat  10  is arranged to move linearly along seat tracks  20 ,  22 , which are adapted to be mounted in a vehicle floor  24  by attachments through apertures  26 ,  28 ,  30 , and  32 , respectively. It is apparent that while one method of mounting the vehicle seat  10  to the vehicle floor  24  is illustrated, any manner of attaching the seat tracks  20 ,  22  to the vehicle floor  24  is contemplated within the description of the multiple embodiments disclosed. The seat tracks  20 ,  22  are generally substantially parallel to one another and serve to permit the vehicle seat  10  to travel to different positions linearly within an interior of a vehicle compartment. 
         [0016]    Along at least one of the seat tracks  20 ,  22 , or at least in close proximity thereto, and generally parallel to at least one of the seat tracks  20 ,  22 , is an inductive vehicle seat position sensor assembly  34 . The inductive vehicle seat position sensor assembly  34  is provided on or relative to the vehicle seat  10  to determine the position of the vehicle seat  10  relative to the tracks  20  as the vehicle seat  10  travels linearly in a fore/aft direction indicated by the arrow  39  provided proximate to the vehicle seat  10 . 
         [0017]    The inductive vehicle seat position sensor assembly  34  has an inductive sensor  36  and a loop coil member  38 . The inductive sensor  36  and the loop coil member  38  of the inductive vehicle seat position sensor assembly  34  are illustrated in  FIGS. 3-4  and are discussed in detail below. 
         [0018]    As depicted in  FIG. 1 , the inductive sensor  36  may mounted directly to the track  20  or adjacent the track  20  so that the circuit board member  60  of the sensor  36  does not move in the fore/aft direction. The loop coil member  38  may be mounted on at least one of the lateral frame members  12 ,  14  in close proximity to the inductive sensor  36 . Since the inductive sensor  36  is affixed in one position relative to the lateral frame members  12 ,  14 , movement of the vehicle seat  10  in the fore/aft direction causes the loop coil member  38  to move linearly in the fore/aft direction relative to the inductive sensor  36  and thereby sense changes in voltage/phase caused through induction. 
         [0019]    In another embodiment, the inductive sensor  36  is mounted on at least one of the lateral frame members  12 ,  14 . The loop coil member  38  is mounted directly to the track  20  or adjacent the track  20  so that the loop coil member  38  does not move in the fore/aft direction. Movement of the vehicle seat  10  in the fore/aft direction as indicated by the arrow  39  proximate the vehicle seat  10  causes the inductive sensor  36  to also move linearly in the fore/aft direction relative to the loop coil member  38  so that the inductive sensor  36  thereby senses changes in voltage/phase caused through induction. 
         [0020]    Referring now to  FIG. 2 , a vehicle safety system with an inductive vehicle seat position sensor system is illustrated and generally referenced by numeral  40 . The vehicle safety system  40  may include inductive vehicle seat position sensor assembly  34 . The inductive vehicle seat position sensor assembly  34  is comprised of the inductive sensor  36  and the loop coil member  38  as described in reference to  FIG. 1 . The inductive vehicle seat position sensor assembly  34  is electrically connected to a remote electronic control unit  42 . In at least one embodiment, the remote electronic control unit  42  is a restraint control module (RCM). The RCM  42  may supply the inductive vehicle seat position sensor assembly  34  with the power as indicated at  44 , and the inductive vehicle seat position sensor assembly  34  sends a signal to the RCM  42  indicative of the linear position in the fore/aft direction of the vehicle seat  10  within the vehicle compartment. The RCM  42  receives additional data signals from safety input devices  46 , shown here as remote crash sensors  48 , occupant classification sensors  50  and seat belt buckle switches  52 . The RCM  42  may have a memory that may be volatile and nonvolatile, EPROM/EEPROM, flash or any other memory, with tables resident therein with values for controlling auxiliary safety devices  54 , shown as seat belt pretensioners  56  and airbags  58 . 
         [0021]    It can be extremely important that all occupant information be made available to the RCM  42  so that all the safety devices  46 ,  54  work together to enhance occupancy safety. For example, it is significant to know the linear position in the fore/aft direction of the vehicle seat  10  within the vehicle so that airbags are inflated at a proper rate and intensity to provide maximum protection to the occupant in the vehicle seat  10 . The input of additional data from the remote crash sensors  48 , occupant classification sensors  50 , and seat belt buckle switches  52  all enhance operation of the seat belt pretensioners  56  and/or airbags  58  during vehicle crash events. Values may be stored in the RCM  42  tables indicative of various intensities and rates of activation for these devices based upon input to the RCM  42 , including linear seat position within the vehicle during a crash event. 
         [0022]    Referring now to  FIGS. 3 and 4 , a detailed view of the inductive vehicle seat position sensor assembly  34  is illustrated. The sensor assembly  34  has an inductive sensor  36  and a loop coil member  38 . The inductive sensor  36  has a circuit board member  60  that is mounted within the vehicle. In at least one embodiment, one of the circuit board member  60  and the loop coil member  38  move relative to one another. In one embodiment, the circuit board member  60  is fixedly mounted within the vehicle and the loop coil member  38  is mounted to a moveable lateral frame member of the vehicle seat so that the loop coil member  38  moves relative to the circuit board member  60 . In another embodiment, the loop coil member  38  is fixedly mounted within the vehicle and the circuit board member  60  is mounted to a moveable lateral frame member of the vehicle seat so that the circuit board member  60  moves relative to the loop coil member  38 . 
         [0023]    The circuit board member  60  is a substrate of fiberglass or other flat insulating sheet material and is an electrically insulating material that has a lightweight. Of course, any suitable circuit board member  60  is contemplated within the scope of the disclosed embodiments. 
         [0024]    As illustrated, a first transmitter coil  62  and a second transmitter coil  64  are mounted on the circuit board member  60 . The first transmitter coil  62  and the second transmitter coil  64  are mounted proximate to the periphery of the circuit board member  60 . The first transmitter coil  62  and the second transmitter coil  64  are excitation coils that may be wires of copper or other conductor imprinted to or adhered to the circuit board member  60 . Although first and second transmitter coils  62 ,  64  are illustrated, any amount of transmitter coils  62 ,  64  are contemplated within the scope of the disclosed embodiments. The first transmitter coil  62  and the second transmitter coil  64  are connected to an integrated circuit  66 . The integrated circuit  66  serves as an excitation and processing circuit. The integrated circuit  66  also has a signal conversion unit  80 . In at least one embodiment, the integrated circuit  66  is a power source for the sensor assembly  34 . 
         [0025]    The first and second transmitter coils  62 ,  64  each receive an input from the integrated circuit  66 . The input may be an alternating current. The first and second transmitter coils  62 ,  64  each produce respective multi-phase magnetic fields that are inductively coupled to a first receiver coil  68  and a second receiver coil  70  by the loop coil member  38 . 
         [0026]    The first receiver coil  68  and the second receiver coil  70  each have a waveform with a period that may be equal. As illustrated, the first receiver coil  68  and the second receiver coil  70  waveforms are out of phase when compared to one another so that each location of the loop coil member  38  along the circuit board member  60  induces voltages with unique phase information in the first receiver coil  68  and the second receiver coil  70 . The measured output voltage/phase of the first receiver coil  68  and the second receiver coil  70  is a function of the position of the loop coil member  38  relative to the circuit board member  60  and thus of the linear position of the movable seat frame with respect to the fixed seat track. The receiver coil voltage and phase measurements are converted to a sensor signal output using a lookup table and interpolating a relative value. The sensor signal output, as seen in  FIG. 2 , is connected to the RCM  42 . 
         [0027]    Referring to  FIG. 4 , the inductive sensor  34  may interface to the RCM  42  via the integrated circuit  66 . In one embodiment, the integrated circuit  66  is an integrated circuit with an analog output signal. In another embodiment, the integrated circuit  66  is an integrated circuit with a digital output signal. Of course, any suitable integrated circuit  66  is contemplated within the scope of the multiple embodiments disclosed. 
         [0028]    The inductive vehicle seat position sensor assembly  34  employs relatively inexpensive printed circuit board  60  with coils implemented using circuit traces, which provides a low cost sensor assembly  34 . Additionally, the inductive vehicle seat position sensor assembly  34  is relatively insensitive to changes in distance between the inductive sensor  36  and the loop coil member  38 , which provides the sensor assembly  34  greater flexibility when mounted within the vehicle than compared to prior art sensor assemblies in vehicles. Furthermore, the inductive vehicle seat position sensor assembly  34  has diagnostic detection capabilities so that the assembly  34  can be tested before the vehicle is fully assembled. The inductive vehicle seat position sensor assembly  34  does not require sensitive, heavy, expensive magnets, which may be influenced by temperature, contaminants, and/or electromagnetic disturbances. Fewer parts are employed because of the use of a single sensor  36  and a single loop coil member  38 . In addition, the inductive vehicle seat position sensor assembly  34  has a continuous (non-discrete) sensing range, which allows for greater sensitivity when compared to prior art sensor assemblies. The inductive vehicle seat position sensor assembly  34  also has a simple construct and does not require the additional weight of other electronics to determine position. 
         [0029]    In  FIG. 5 , a representation of seat track position in relation to voltage of the signal assembly is illustrated. The x-axis  100  is linear seat position, ranging from full rear to full forward position of the seat, and the y-axis  102  is sensor output voltage. The relationship between linear seat position and voltage is depicted at  104 , and can be understood to be linear. When the seat is in the rearward portion  106 , the voltage is relatively low, and as the seat travels linearly toward the full forward position  108 , the voltage is relatively high. In this depiction, the voltage ranges from 0.25 volts to 4.75 volts, but any range of voltages may be seen, the only limitation being that the relationship between fore and aft seat position and voltage is linear. 
         [0030]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.