Abstract:
A seat position sensor for a vehicle including: a sensing portion configured to sense a position of a vehicle seat with respect to a part of the vehicle; and a mounting portion coupled to the sensing portion, wherein the mounting portion includes an integral locking pin configured to secure the seat position sensor to a portion of the vehicle. A seat position sensor including a housing having an internal surface defining an opening and a seal disposed in the opening to create a cavity for housing electrical circuitry is also provided. A seat position sensor circuit is also provided to enable testing of a varistor without adversely affecting other portions of the circuit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/328,166, filed Oct. 10, 2001, the teachings of which are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to an apparatus with an integral locking pin and cavity seal. In particular, such apparatus may be a position sensor utilized in vehicle applications. A position sensor circuit is also provided.  
         BACKGROUND OF THE INVENTION  
         [0003]    Many vehicles are equipped with sensors for sensing the position of various objects. One such sensor may be a seat track position sensor to sense the position of a vehicle seat. The position of the vehicle seat may be utilized in a variety of other internal vehicle systems including air bag deployment systems, seat position memory systems, seat occupancy sensing systems, and other such systems.  
           [0004]    In an air bag deployment system, the sensor may be configured to sense the position of the seat to a predetermined accuracy. In one system, the sensor may be a U-shaped sensor with a magnet in one leg of the U-shaped sensor and a magnetic sensor, e.g., a Hall sensor, in the other leg. The U-shaped open cavity of the sensor may be configured to accept a flange. The flange may interrupt the magnetic field such that the Hall sensor senses different magnetic field conditions depending on the position and shape of the flange. A control signal indicative of the various sensed magnetic field conditions may then be input to an air bag deployment controller.  
           [0005]    In this way, the air bag deployment force may be controlled depending on the position of the seat. For example, if the seat is in a forward position closer to the front dashboard or steering wheel, the controller may provide instructions to deploy the air bag with less force. In contrast, if the seat is sufficiently far from the front dashboard or steering wheel, the controller may provide instructions to deploy the air bag with maximum force.  
           [0006]    Seat track position sensors are packaged and provided in a variety of ways. Typically, a separate locking pin or fastener is needed in order to lock the sensor in place after the sensor is installed on a mounting bracket. This requires the installer to locate this separate component, which may be unavailable, damaged, or otherwise the incorrect component.  
           [0007]    In addition, seat track position sensors typically also require a separate potted printed circuit board (PCB) assembly. This requires a potting operation to seal this separate potted PCB assembly. This separate potted PCB assembly and potting operation requires expensive assembly and process operations, and may not provide a sufficient seal for the PCB.  
           [0008]    In addition, a seat track position sensor may include a seat track position sensor circuit having a variety of electrical components including a varistor and a Hall switch. The varistor, as known in the art, protects the circuit against high voltage power surges above the rated breakdown voltage level for the varistor. Typically, the breakdown voltage for the varistor was much lower than the breakdown voltage for the Hall switch. However, as voltage input requirements have increased, the breakdown voltage of the varistor has necessarily increased and may now overlap with the breakdown voltage of the Hall switch. As such, post production testing of such a circuit may give false indications of the functionality of the varistor given the Hall switch could inadvertently turn on first when testing for breakdown of the varistor.  
           [0009]    Accordingly, there is a need in the art for an apparatus with an integral locking pin and improved cavity seal, which can be used in a variety of applications including a vehicle seat position sensor. There is also a need for a seat position sensor circuit permitting proper post production testing of a varistor when the varistor&#39;s breakdown voltage may overlap that of an associated Hall switch.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    A seat position sensor for a vehicle consistent with the invention includes: a sensing portion configured to sense a position of a vehicle seat with respect to a part of the vehicle; and a mounting portion coupled to the sensing portion, wherein the mounting portion includes an integral locking pin configured to secure the seat position sensor to a portion of the vehicle.  
           [0011]    According to another aspect of the invention, there is provided an apparatus including: an integral locking pin having a head portion and a leg portion; and a mounting portion for mounting the apparatus to a mounting location with the integral locking pin, the mounting portion including a member having a first surface and a second surface orthogonal to the first surface, wherein the first surface and the second surface define a first portion of a cavity configured to accept the head portion of the integral locking pin when the integral locking pin is fully inserted into the cavity, and wherein the mounting portion further includes a tapered surface defining a second portion of the cavity configured to accept the leg portion of the integral locking pin when the locking pin is fully inserted into the cavity.  
           [0012]    According to a further aspect of the invention, there is provided a seat position sensor for sensing the position of a vehicle seat relative to a portion of a vehicle including: a sensor portion configured to sense the position of the vehicle seat and provide a seat position control signal; a housing having an internal surface defining an opening; a seal disposed in the opening to create a cavity defined by a portion of the internal surface of the housing and an internal surface of the seal; and electrical circuitry disposed in the cavity and configured to accept the seat position control signal.  
           [0013]    According to yet another aspect of the invention, there is provided a seat position sensor circuit including: a pair of input/output terminals; a varistor coupled to the terminals; an energy storage element coupled in parallel with the varistor; a forward biased diode having an input terminal and an output terminal, the input terminal coupled to the varistor and the output terminal coupled to the energy storage element; wherein a negative voltage may be applied at the pair of input/output terminals to test the varistor and wherein the forward biased diode would isolate any other electrical components coupled to the output terminal of the diode.  
           [0014]    Another seat position sensor circuit consistent with the invention includes: a varistor coupled to a pair of terminals; and a forward biased diode having an input terminal and an output terminal, the input terminal coupled to the varistor and the output terminal coupled to a Hall switch, wherein a negative voltage may be applied at the pair of terminals to test the varistor and wherein the forward biased diode would isolate the Hall switch from the negative voltage.  
           [0015]    A method of testing a varistor of a seat track position sensor circuit consistent with the invention includes the steps of: applying a negative voltage to test a break down voltage of the varistor; and blocking the negative voltage to effectively isolate other components of the circuit.  
           [0016]    A method of securing a seat position sensor to a vehicle consistent with the invention includes the steps of: locating the sensor in proximity to a mounting portion of the vehicle, the mounting portion having an opening; and forcing an integral locking pin of the sensor into the opening of the mounting portion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    Advantages of the present invention will be apparent from the following detailed description of exemplary embodiments thereof, which description should be considered in conjunction with the accompanying drawings, in which:  
         [0018]    [0018]FIG. 1 is a simplified plan view of a vehicle having a seat track position sensor;  
         [0019]    [0019]FIG. 2 is a side sectional view of an apparatus including an integral locking pin consistent with the present invention;  
         [0020]    [0020]FIG. 3 is a cross sectional view along the line  3 - 3  of FIG. 2 illustrating details of an integral locking pin consistent with the present invention;  
         [0021]    [0021]FIG. 4 is a cross sectional view illustrating an exemplary cavity and seal for electronic circuitry consistent with the present invention; and  
         [0022]    [0022]FIG. 5 is a circuit diagram of an exemplary seat track position sensor circuit consistent with the invention. 
     
    
     DETAILED DESCRIPTION  
       [0023]    The present invention relates generally to an apparatus having an integral locking pin and improved cavity seal. A seat position sensor circuit is also provided. The present invention is described with reference to a seat track position sensor to provide seat position information to a variety of internal vehicle systems. Those skilled in the art, however, will recognize that an apparatus consistent with the present invention may be utilized in a host of other environments. Thus, it is to be understood that the present invention is not limited to the illustrated exemplary embodiments described herein. Rather, the present invention may be incorporated in a wide variety of devices without departing from the spirit and scope of the present invention.  
         [0024]    Turning to FIG. 1, a simplified plan view of an exemplary vehicle  100  having a seat track position sensor  102  is illustrated. The seat track position sensor  102  provides position information for the seat  104 . In one exemplary embodiment, the seat track position sensor  102  may provide seat position control signals to a controller  106 . The controller  106  may then be responsive to such control signals to control the deployment force of an associated air bag  110 . For example, if the seat is in a forward position closer to the front dashboard or steering wheel, the controller  106  may provide instructions to deploy the air bag  110  with less force. In contrast, if the seat is sufficiently far from the front dashboard or steering wheel, the controller  106  may provide instructions to deploy the air bag  110  with maximum force.  
         [0025]    In other embodiments, the seat track position sensor  102  may provide position information for use in seat position memory systems. In such instances, a seat position may be saved in memory, and a user may activate the seat to move to the saved seat position.  
         [0026]    In yet another embodiment, a seat track position sensor  102  may be configured to sense the presence of a person in a construction vehicle seat. When a person occupies the seat, the weight of the person may force a shunt into an open cavity of a sensor having a magnet in one side of the cavity and a Hall sensor in the other side. The sensor then, in turn, may provide a control signal to a separate external controller indicating normal operation of the construction equipment may begin. If, however, the person is then accidentally removed from the seat, the shunt may leave the open cavity and a separate control signal would be indicated. An external controller may use this separate control signal to shut down the running engine of the construction equipment ensuring higher safety.  
         [0027]    Turning to FIG. 2, a side sectional view of an apparatus  200  including an integral locking pin  202  consistent with the present invention is illustrated. The apparatus  200  may be a seat track position sensor in one embodiment having a mounting portion  220  and sensing portion  222 . The mounting portion advantageously includes the locking pin  202  integral with the sensor such that the installer does not need a separate locking pin that may be unavailable, damaged, or otherwise the incorrect pin. An installer simply needs to apply a downward force to the integral locking pin  202  to push the locking pin though a receptive opening in a mounting plate  214  of a vehicle.  
         [0028]    Turning to FIG. 3, a cross sectional view of the apparatus  200  taken along the line  3 - 3  is illustrated. The integral locking pin  202  is illustrated in a first integral position in which the pin  202  is ready for mounting. In general, the integral locking pin  202  has a head portion  340  and a leg portion  342 . The leg portion  342  may further include a first leg  346  and a second leg  348  which have interior surfaces  347 ,  349  that define a slot  312 . The slot  312  may also be defined by an interior surface of a leg portion  342  of the integral locking pin  202  where the leg portion has a hollow cylindrical type shape. The locking pin  202  may further include a first radial protrusion  304  and a second radial protrusion  306  extending radially from a centerline axis  370  of the integral locking pin  202 .  
         [0029]    The mounting portion of the sensor further includes components that define a cavity  360  to work in cooperation with the above identified features of the integral locking pin  202 . The cavity  360  may have a first portion  362  and a second portion  364 . A member  350  of the sensor may have a surface  351  and a surface  352  which is orthogonal to surface  351  that together define the first portion  362  of the cavity  360 . This first portion  362  of the cavity  360  is sized to receive the head portion  340  of the integral locking pin  202  when the integral locking pin is fully inserted into the cavity  360 . A tapered surface  316  of the mounting portion of the sensor defines the second portion  362  of the cavity  360 .  
         [0030]    In operation, the integral locking pin  202  may by have a variety of positions to simplify mounting. FIG. 3 illustrates the pin  202  in a first integral position in which the pin  202  is prepared to assist with mounting of the sensor to the mounting plate  214 . If an outwardly exerted force is applied to the pin, the first radial portion  304  of the pin  202  contacts a surface portion of member  350  and thus prohibits the pin  202  from being extracted from the sensor. As such, the locking pin  202  advantageously remains integral with the sensor until the sensor or apparatus is ready for final assembly in the correct assembly location.  
         [0031]    Once the sensor or apparatus is located in a position ready for assembly, e.g., a seat position sensor for mounting to a mounting plate of a vehicle, a downward force is exerted by an installer on the integral locking pin  202 . As the pin  202  moves downward, the tapered surface  316  forces the leg portion  342  of the pin  202  closer together thereby narrowing the slot  312  opening. As this occurs, the second radial protrusion  306  is forced or deflected inward allowing it to pass through the opening defined by the member  350  and also allowing the second radial protrusion to pass through the narrow opening defined by the narrow end of the tapered surface  316 .  
         [0032]    If an outwardly exerted force is applied to the pin once it is fully inserted into the cavity  360 , the second radial portion  306  of the pin  202  contacts a surface portion on the exterior of the cavity and thus prohibits the pin  202  from being extracted from the sensor. The slot  312  is outwardly biased sufficiently to maintain the integral locking pin in its fully assembled position. Advantageously, a staged pin assembly consistent with the present invention is thereby incorporated without any additional components. Those skilled in the art will recognize a plurality of radial protrusions may be provided on a locking pin  202  for different applications without departing from the scope of the present invention.  
         [0033]    Turning to FIG. 4, another embodiment of the present invention including a seal  402  for protecting internal electrical circuitry, e.g., for protecting a PCB  404 , is illustrated. In the exemplary embodiment of FIG. 4, an exemplary seal  402  is formed and positioned to adequately seal a PCB  404  in a PCB cavity  406 . The other portions of the cavity  406  are formed by the internal surfaces  411   a,    411   b,    411   c  of the housing  411 . The cavity seal  402  may be formed by an injection-molded elastomer and may further include a retainer plate  408 .  
         [0034]    The injection-molded elastomer may be injected into a mold exterior to the apparatus  400 . The retainer plate  408  may be stainless steel, which provides a rigid structure to the cavity seal  402 . The retainer plate  408  also provides gripping pressure to the seal  402  to assist gripping the seal to the internal housing surfaces  411   a,    411   c.  The seal  402  may include an elastomer type that provides an adequate seal between the seal  402  and the internal housing surfaces  411   a,    411   c.    
         [0035]    For instance, the formed elastomer may be sufficiently flexible so that the seal can be compressed and inserted in the opening  414 . When the seal  402  reaches its sealed position as illustrated in FIG. 4, the elastomer attempts to expand against the internal housing surfaces  411   a,    411   c  thus providing a tight seal that prevents leakage of unwanted contaminants into the cavity  406 . Additional sealing features are provided for the electrical terminals to prevent leakage along this possible leak path.  
         [0036]    Turning to FIG. 5, another embodiment of the present invention including an exemplary seat position sensor circuit  500  is illustrated. The seat position sensor circuit  500  generally includes a Hall switch  502 , an energy storage element, e.g., a capacitor  504 , a diode  506 , a varistor  508 , and a resistor  510 . Such an exemplary circuit  500  may be located on the PCB  404  of the sensor  400  illustrated in FIG. 4.  
         [0037]    The varistor  508 , as known in the art, protects the circuit  500  against high voltage power surges. When a voltage surge exceeding a predetermined voltage level or varistor voltage level is applied, the varistor suppresses such voltage by rapidly decreasing its resistance and creating a shunt path for the voltage surge. If such a voltage surge does not exceed the varistor voltage level, the varistor acts as a capacitor.  
         [0038]    Once the circuit is constructed, various tests are typically undertaken to test the functionality of various components of the circuit  500 , e.g., the varistor  508 . Advantageously, the exemplary circuit  500  enables testing of the varistor  508  with a current limited negative voltage which gives a true sense of the varistor functionality without inadvertently turning the Hall switch on. To accomplish this, the varistor  508  is connected in parallel with the input/output terminals  512   a,    512   b  and the forward biased diode  506  is connected in series between the varistor  508  and the capacitor  504 . As such, this circuit  500  enables post circuit production testing to apply a current limited negative voltage to the circuit  500  to verify proper operation of the varistor  508 . The forward biased diode  506  prevents such current limited negative voltage from inadvertently turning on the Hall switch  502 . As is known in the art, checking the breakdown voltage with negative or positive voltage is a legitimate check of the functionality of a varistor, since varistors are inherently bilateral devices.  
         [0039]    The embodiments that have been described herein, however, are but some of the several which utilize this invention and are set forth here by way of illustration but not of limitation. It is obvious that many other embodiments, which will be readily apparent to those skilled in the art, may be made without departing materially from the spirit and scope of the invention as defined in the appended claims.