Abstract:
A method and apparatus for controlling the deployment of a passive inflatable restraint system wherein driver and passenger air bags are employed each having two independently actuatable gas generators of the same or different sizes which are activated in a fixed time sequence. The sequence is timed to provide an initial low inflation rate to just open the airbag container and initially deploy the airbag followed by a higher gas flow rate to complete filling of the cushion. An electronic control unit containing a control algorithm and connected to external sensors monitors vehicle decelerations, detects impacts, and determines if impact severity warrants deployment of an airbag for occupant protection. The external sensors include one or more sensors located in the forward portion of the vehicle to provide early impact detection and crash severity indications; a weight based occupant detection system located in the passenger seat to identify infants and small children and provide airbag suppression; and a seat belt mode or seat belt tension sensor to determine the presence of a cinched child seat and provide additional airbag suppression. The control algorithm monitors the above described sensors and if a deployment is required, a signal for activating the first initiator and a second signal for activating the second initiator are provided, the second signal being delayed a predetermined time after the first signal is generated.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Patent Application Serial No. 60/248,997 filed Nov. 15, 2000, the contents of which are incorporated herein by reference thereto. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates generally to vehicle passive inflatable restraint systems and, more particularly, to an air bag deployment system.  
         BACKGROUND  
         [0003]    Driver side or passenger side passive inflatable restraint (PIR) systems typically include an air bag stored in a housing module within the interior of the vehicle in close proximity to either the driver or one or more passengers. PIR systems are designed to actuate upon sudden deceleration so as to rapidly deploy an air bag to help restrain the movement of the driver or passengers. During deployment, gas is emitted rapidly from an inflator into the air bag to expand it to a fully inflated state.  
           [0004]    Air bag passive restraint systems include an inflator, which produces gas to inflate an air bag cushion. There are several types of inflators for air bag modules. One type is the cold gas inflator wherein a pressure vessel contains stored pressurized gas. The pressure vessel communicates with the cushion through various types of rupturable outlets or diaphragms. Another type is the pyrotechnic gas generator wherein a propellant is ignited and the resultant gas flows through an outlet into the cushion. A third type is the hybrid or augmented type. This type includes a pressure vessel containing stored pressurized gas and a pyrotechnic heater. When the heater is ignited, the stored gas from the pressure vessel is heated (expands) resulting in a greater gas volume to the airbag cushion.  
           [0005]    All of these inflator types can be configured as dual stage inflators. Using two separate initiators, the cushion can be inflatedto a low pressure at a relatively low rate under some deployment conditions; and to a higher pressure at a relatively high rate under other deployment conditions. This can be accomplished, for example, in a hybrid type inflator by providing the pressure vessel with two separately ignitable heater&amp;  
         SUMMARY OF THE INVENTION  
         [0006]    The invention consists of a restraint system having novel airbag modules, airbag suppression logic using a passive occupant detection system (PODS), seat belt inputs either from an automatic locking retraction (ALR) switch or belt tension sensor (BTS), and deployment logic to appropriately control the airbag deployment and assist in the restraint of an occupant.  
           [0007]    Each airbag module contains an inflator having a first and second initiator each being fired during an air bag deployment, with the second initiator being ignited after a pre-determined time delay. Each initiator provides gas flow to an air bag which is deployed in a two-step sequence. Both initiators will be fired for any deployment, leaving no live squibs in the air bag module after deployment. The first initiator provides a low inflation rate and contributes an initial volume of gas sufficient to just deploy the airbag cushion. After the cushion has begun to deploy, the second initiator is firedand provides additional gas at a higher inflation rate into the cushion to provide the required restraint capability. The higher gas flow rates are initiated after the cushion has been deployed.  
           [0008]    A deployment command consisting of two signals will be transmitted by a sensing and diagnostic module (SDM) to each airbag module when a sufficiently severe vehicle impact occurs as to require airbag deployment. Should the passive occupant detection system (PODS) determine that a small child or a child seat or infant seat is occupying the passenger seat, the deployment command will be suppressed and not sent to the airbag modules. The PODS uses the measured weight of the occupant to make this determination.  
           [0009]    Since some child seats require cinched seat belts to retain them in position, a switch detecting the activation of the automatic locking retractor feature or a seat belt tension sensor is employed to correct the PODS weight estimation for the additional load produced by the cinched seat belt. Alternatively, the ALR or BTS switches may be used to suppress the deployment command directly.  
           [0010]    The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:  
         [0012]    [0012]FIG. 1 is an exploded perspective view of a driver side air bag module;  
         [0013]    [0013]FIG. 2 is a view along lines  2 - 2  of FIG. 1 and shows a two stage pyrotechnic driver inflator;  
         [0014]    [0014]FIG. 3 is a view along lines  3 - 3  of FIG. 1;  
         [0015]    [0015]FIG. 4 is a cross-sectional view of a driver airbag module in a first deployment configuration;  
         [0016]    [0016]FIG. 5 is a cross-sectional view of a driver airbag module in a second deployment configuration;  
         [0017]    [0017]FIG. 6 is an exploded perspective view of a passenger side air bag module;  
         [0018]    [0018]FIG. 7 is a cross-sectional view of a two-stage pyrotechnic passenger side inflator;  
         [0019]    [0019]FIG. 8 is a cross-sectional view of a hybrid passenger side inflator;  
         [0020]    [0020]FIG. 9 is a diagrammatic view of a two-stage driver side inflator and control system;  
         [0021]    [0021]FIG. 10 is a diagrammatic illustration of an occupant protection system;  
         [0022]    [0022]FIG. 11 is a flowchart illustrating portions of a command sequence employed by the FIG. 10 embodiment; FIG. 12 is a cross sectional view of a seat belt tension assembly without tension;  
         [0023]    [0023]FIG. 13 is a cross sectional view of the seat belt tension of a FIG. 1 assembly with tension;  
         [0024]    [0024]FIG. 14 is a cross sectional view of a seat belt tension assembly without tension;  
         [0025]    [0025]FIG. 15 is a view along lines  15 - 15  of FIG. 14;  
         [0026]    [0026]FIGS. 16 and 17 are cross sectional views of alternative seat belt tension assemblies;  
         [0027]    [0027]FIGS. 18 and 19 are exploded views of alternative embodiments of the present invention;  
         [0028]    [0028]FIG. 20 is a schematic of a Hall effect device for use with the present invention; and  
         [0029]    [0029]FIG. 21 is a schematic of a Hall effect device for use with the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]    Referring now to FIG. 1, a driver&#39;s side air bag module, generally designated at  10  is illustrated. Air bag module  10  includes a cover  12 , an air bag cushion  14 , a retainer  16 , a mounting plate  18 , and an inflator assembly  20 . The inflator assembly has a plurality of vent apertures  22  which are in fluid communication with an opening  24  of air bag cushion  14 . The inflator assembly through apertures  22  releases a volume of gas into the air bag cushion. The volume of gas released into the air bag cushion is sufficient to deploy the air bag cushion through cover  12 .  
         [0031]    Referring now to FIGS. 2 and 3, inflator assembly  20  has an inflator housing  22  defining an interior inflator housing cavity  25 . In addition, inflator assembly  20  has a peripheral flange  26  for mounting inflator assembly  20  to air bag module  10 . Positioned within cavity  25  are a first initiator  28  and a second initiator  30 . Initiator  28  has an initiator housing  32 . Initiator housing  32  has a plurality of vent apertures  34 . A propellant  36  is stored within housing  32  of initiator  28 . Propellant  36  is ignited by a squib  38  which fires in response to a signal received from a controllor in response to signals received from a plurality of sensors positioned throughout the vehicle in order to determine whether deployment of the airbags is required. In an exemplary embodiment, propellant  36  is a pyrotechnic-type solid propellant and alternatives such as pressured gas are also contemplated to be used.  
         [0032]    Accordingly, and as the squib ignites the propellant, the resultant gas flows through an outlet pathway to the cushion. In an exemplary embodiment, the gas of initiator  28  flows through vent openings  34  into cavity  25  and into air bag opening  24  through vent apertures  22 .  
         [0033]    Similarly, second initiator  30  has a squib  40  for igniting a propellant  42  that passes through vent openings  44  in a housing  46  of second initiator  30 . In an exemplary embodiment, typically, first initiator  28  is larger than second initiator  30 . Accordingly, the resultant gas generated by first initiator  28  is more than the gas generated by second initiator  30 .  
         [0034]    In addition, and in accordance with an exemplary embodiment, a preferred mode of the deployment of air bag cushion  14  of air bag module  10  is as follows: first, initiator  28  fires to provide an amount of gas for deploying air bag cushion  14  into a first deployment position (FIG. 4). The amount of gas provided to air bag cushion  14  is sufficientto cause cushion  14  to break through a tear seam  48  of cover  12 . Alternatively, and in applications where cover  12  or a portion thereof is dislodgable from module  10  the amount of gas is sufficient to dislodge cover  12 . Second, initiator  30  fires to provide a second amount of gas to air bag cushion  14  in order to fully deploy air bag cushion  14  (FIG. 5).  
         [0035]    Referring now to FIG. 6, a passenger side air bag module  50  is illustrated. Air bag module  50  has a cover or door  52 , an inflatable air bag cushion  54 , a housing assembly  56  and an inflator assembly  58 .  
         [0036]    Referring now to FIG. 7, an inflator assembly  60  is illustrated. Here inflator assembly  60  has a central opening  62  that once installed into a housing of a passenger side air bag module is in fluid communication with an opening of an inflatable air bag cushion. Inflator assembly  60  has a first initiator  64  and a second initiator  66 . First initiator  64  has an outer housing  68  for containing a propellant  70 . In addition, first initiator  64  has an exhaust manifold  72  in fluid communication with the propellant of housing  68 . Exhaust manifold  72  has a plurality of vent openings  74 . Vent openings  74  are in fluid communication with an exhaust plenum  76  that is in fluid communication with central vent opening  62 . A first squib  78  provides a means for igniting the propellant in housing  68 . In addition, first squib  78  is connected to a central processor or controller which provides a signal to fire first squib  78  in response to a signal or plurality of signals received from a plurality of sensors positioned about the vehicle. The plurality of sensors provide information about the impact severity which in response to adverse conditions sends a signal to authorize first squib  78  to fire.  
         [0037]    Second initiator  66  has a squib  82  for igniting a propellant  84  whose gas passes through vent openings  86  in an exhaust manifold  88 . The first initiator  64  is larger than second initiator  66 . Accordingly, the resultant gas generated by first initiator  64  is larger than the gas generated by second initiator  66 .  
         [0038]    In addition, and in accordance with an exemplary embodiment, a preferred mode of deployment of air bag cushion  54  of air bag module  50  is similar to the deployment of air bag module  10  in which the first initiator fires first to provide a first amount of gas for deploying the air bag cushion into a first deployment position. The amount of gas provided to the air bag cushion is sufficient enough to the cause the cushion to break through a tear line of the air bag cover, and the second initiator fires after a fixed time delay to provide a second amount of gas to the air bag cushion in order to fully deploy the air bag cushion.  
         [0039]    Accordingly, the air bag modules with inflators that have two initiators provide deployment by creating a gentler inflation curve (S-curve) with less punch out force in the first stage (first initiator firing) to break the air bag cover tear seam and get the air bag out.  
         [0040]    The first ignition will always be followed by a second ignition in a fixed time delay to produce more gas into the cushion resulting in a higher inflation slope when the second initiator is fired. The module uses a sequential deployment of the inflator initiators.  
         [0041]    Moreover, there will be no unfired initiator left in the air bag module.  
         [0042]    Referring now to FIG. 8, an alternative configuration of a passenger side inflator assembly is illustrated.  
         [0043]    Referring now to FIG. 9, a control system  100  is illustrated. Control system  100  is used in the deployment of an air bag module using an inflator with a pair of initiators with a sequential firing of both initiators in accordance with an exemplary embodiment of the present invention, for example, inflator assembly  20 . Of course, other types of inflator assemblies with multiple initiators for air bag deployment are contemplated for use with control system  100 . In addition, both passenger side and driver side inflator assemblies are contemplated for use with control system  100 .  
         [0044]    A sensing and diagnostic module (SDM)  110  receives a plurality of inputs  102  from a plurality of sensors  104  and determines whether an air bag deployment is necessary. If the SDM determines that an air bag deployment is necessary, SDM  110  generates a first signal  108  and a second signal  106 . The first signal is received by and instructs a first squib of a first initiator to fire. The second signal is received by and instructs a second squib of a second initiator to fire. For example, squibs  40  and  38  of assembly  20 .  
         [0045]    In accordance with an exemplary embodiment of the present invention, a time delay is applied to delay the generation of second signal  106 . The time delay is generated by a logic system  112  of SDM  110 . Accordingly, and as plurality of signals  102  are received within SDM  110  a decision to deploy the air bag is determined. If SDM  110  determines that deployment is necessary second signal  106  is delayed a predetermined amount of time to facilitate the deployment of an air bag in a manner including but not limited to the deployment illustrated in FIGS. 4 and 5.  
         [0046]    The SDM receives signals (such as vehicle decelerations and impact sensors) in order to determine whether an air bag should be deployed. One of sensors  104  is an electronic frontal sensor (EFS), which is an external sensor mounted in the engine compartment, typically on the radiator tie bar to supplement the internal sensors of the SDM in detecting and responding in a timely manner to threshold impacts such as the offset deformable barrier impact. In addition, the SDM has its own internal sensors for measuring vehicle decelerations. The EFS will be used to enhance the overall sensing system performance by providing early information to the SDM to determine airbag deployment.  
         [0047]    Accordingly, and if the appropriate signals from the sensors located throughout the vehicle are received, a signal for initiating the deployment of an air bag is generated by the SDM.  
         [0048]    In an exemplary embodiment, the preferred delay of second signal  106  with respect to  108  is 20 milliseconds. Accordingly, first initiator 30 fires 20 milliseconds before second initiator  28 . Of course, and as applications may require, the delay value may be greater than or less than 20 milliseconds.  
         [0049]    Preferably, the delay will be in a 5-35 millisecond range, however, and as applications may require, delays outside this range are contemplated to be within the scope of invention.  
         [0050]    In addition, it is noted that the system will always fire both squibs and follow a fixed time sequence deployment. The squibs are fired once the SDM has determined that airbag deployment is required. Moreover, this allows low level deployment in the first stage with overall high-level gas discharge from both the first and second stages.  
         [0051]    The amount of delay and resultant gas generated by initiators  28  and  30  will depend upon the vehicle performance characteristics as well as the necessary force required to dislodge the cover or door which is placed over the air bag. Accordingly, it is contemplated that these values may differ for applications in multiple types of vehicles.  
         [0052]    As an alternative embodiment, and as illustrated by the dashed lines in FIG. 9, a passive occupant detection system (PODS)  114  provides an input into the SDM. PODS  114  is a sensing system installed in the seat cushion which senses the weight of the occupant to determine if infants, small children or an adult are present (in the passenger seat) and if necessary, instructs the SDM to utilize air bag suppression. Thus, the system will suppress the passenger side airbag if the PODS has detected and determined that smaller sized children are in the passenger seating position. Separate from or as part of the PODS, a seat belt mode sensor (ALR SW) or belt tension sensor (BTS) may also be provided to detect the installation of a child seat and modify or replace the decision of the PODS system to suppress the airbag.  
         [0053]    As yet another alternative, second squib  38  is equipped with a mechanical delay to provide the necessary delay in firing of the second squib. In this embodiment, signals  106  and  108  may be fired atthe same time or alternatively a single signal may be sent to one squib and the second squib can be fired by a mechanical delaying mechanism between the two squibs. This will allow the SDM to send a signal to only one squib (e.g., one signal for a driver airbag module and one for a passenger airbag module).  
         [0054]    Alternative inflator assemblies may include a hybrid inflator wherein the first initiator is a pyrotechnic device which is used as a heater to expand a gas stored in a pressure vessel. A second initiator is provided to further heat and expand the stored gas. Accordingly, the first initiator is fired first to initially expand the gas and just deploy the airbag cushion, then the second initiator is ignited following a time delay which causes the resultant gas to expand further and completely fill the cushion.  
         [0055]    The deployment of the air bag modules as disclosed herein provides a means for deploying an air bag cushion in a manner which causes the air bag module to always fire both initiators leaving no unfired charges in the air bag module after it has deployed.  
         [0056]    While only two types of air bag modules are illustrated herein, it is contemplated that in accordance with the present invention the inflators described herein may be used in other air bag modules, including but not limited to, driver side air bag modules, passenger side air bag modules and side impact air bag modules.  
         [0057]    Referring now to FIG. 10, a vehicle occupant protection system  300  is illustrated. System  300  includes a driver airbag (DAB)  310 . In an exemplary embodiment, driver airbag  310  is an air bag module capable of deploying an air bag in a two step manner. This is achieved in one embodiment by adding an inflator with two charges and two initiators and firing the initiators in sequence with a predetermined fixed time delay.  
         [0058]    For example, one such driver airbag  310  may be the airbag module described in FIGS.  1 - 5 . A clock spring coil  312  (coil) is configured to transmit a deployment current independently to each initiator of the air bag module from the vehicle electrical system via the SDM into the rotating steering wheel and to the driver airbag module using a continuous coil of wire or similar device.  
         [0059]    Seat belt switches (SBS)  314  are located in the seat beltbuckles and provide a signal indicating the proper attachment and usage of seat belts. This information is provided to the system control algorithm to tailor system performance for belted and unbelted occupants such as modifying the severity threshold parameters for deployment.  
         [0060]    A passenger airbag (PAB)  316  is also incorporated into system  300 . In an exemplary embodiment, passenger airbag  316  is an air bag module capable of deploying an airbag in a two step manner. This is achieved in a manner similar to the driver side air bag as well as the modules illustrated in FIGS.  6 - 9 . Also, the passenger airbag may utilize a Biased Deployment Flap as disclosed in and commonly owned and assigned U.S. Pat. No. 5,348,343.  
         [0061]    Alternatively, passenger airbag  316  is an airbag module wherein the deployment is achieved through the use of alternative charges being fired and/or venting schemes in which the gas produced by the inflator is varied accordingly.  
         [0062]    A Passive Occupant Detection system (PODS)  318  includes a seat mounted sensor used to detect the approximate size of the passenger occupant by weight. The sensor is used by the control system to suppress the passenger airbag in accordance with pre-determined criteria.  
         [0063]    An automatic locking retractors switch (ALR SW)  320  is a system that assumes that the use of a combination ELR/ALR seat belt system which normally operates in the emergency locking retractor (ELR) mode. When the belt is fully extended or above a pre-determined length, the belt system switches to an automatic locking retractor mode for use in securing certain infant and child seats. The ALR switch detects when the seat belt is in the ALR mode and provides this information to the control system. The control system uses this information in conjunction with the PODS data to determine if a child or infant seat is present in the passenger seat and the control system will suppresses the airbag, if appropriate.  
         [0064]    One contemplated automatic locking retractor switch is of the type described and disclosed in commonly owned and assigned U.S. provisional patent application Serial No. 60/247,309 filed on Nov. 9, 2000, attorney docket no. DP 303497.  
         [0065]    Another type of seat belt tension sensing device for determining whether an infant or child seat is secured by the seat belt and for providing a signal to the sensing and diagnostic module is of the type described and disclosed in commonly owned and assigned U.S. patent application Ser. No. 09/796,237, filed Feb. 28, 2001. (FIGS.  12 - 21 ).  
         [0066]    Other contemplated types of seat belt tension sensing devices are described and disclosed in commonly owned and assigned U.S. patent applications Ser. Nos. 09/415,533, filed Oct. 8, 1999 and 09/482,298 filed Jan. 1, 2000.  
         [0067]    A sensing and diagnostic module (SDM)  322  is an electronic control module that senses and diagnoses signals from sensors and determines if the air bags, pre-tensioners, etc. should be deployed. The SDM uses inputs from both internal and external sensors to determine if air bag and/or pretensioner suppression is required.  
         [0068]    In an exemplary embodiment, the SDM follows the logic shown in FIG. 11, which illustrates portions of a command sequence of the control algorithm of the SDM. Of course, and as applications require, other control algorithms and/or sequences may be employed with the present invention.  
         [0069]    The SDM also contains its own internal sensors for measuring vehicle decelerations for arming and discriminating purposes. In addition, an external electronic frontal sensor  324  is positioned typically at the front of the vehicle to provide early detection of various impacts. The electronic frontal sensor (EFS) is an external sensor mounted in the engine compartment typically mounted on the radiator tie bar to supplement the internal sensors of the SDM in detecting and responding in a timely manner to threshold impacts such as the offset deformable barrier impact.  
         [0070]    In addition, system  300  includes a telltale light  326 . Telltale light  326  is a light mounted in the passenger compartment positioned to indicate the status of passenger airbag deployment activation. When the passenger side air bag is suppressed, the telltale light will be turned on indicating the passenger airbag is suppressed.  
         [0071]    As an alternative, seat belt pre-tensioners (P/T)  328  are included into system  300 . Seat belt pre-tensioners  328  are pyrotechnic devices that remove slack from the seat belt.  
         [0072]    Referring now to FIG. 11, a flowchart  350  illustrates portions of a control algorithm wherein the passenger air bag deployment and other safety restraints are partitioned into a two-step process. A first step  352  is illustrated by the dashed lines in FIG. 11 here first step  352  determines whether airbag suppression is necessary while also determining whether an infant car seat is present. A decision node  354  determines whether the automatic locking retractor switch  320  has been activated or a seat belt cinching sensor detected enough tension of the seat belt webbing. If so, a command step  356  instructs the SDM to suppress the passenger side air bag. If on the other hand, the ALR has not been activated, the PODS  318  determines whether an occupant smaller than a pre-determined size and weight is present in the passenger seat. One example of a predetermined size and weight is that of a six-year-old test dummy or substantial equivalent thereof. Of course, other predetermined sizes and weights may be used with the PODS system. This is performed through the use of a passenger seat sensor or other sensing means.  
         [0073]    A decision node  358  determines whether the occupant in the passenger seat is less than a prescribed weight. For example, FIG. 11 illustrates a decision node with an  80  pound prescribed weight. Of course, and as applications may require this value can vary.  
         [0074]    If decision node  358  determines that the occupant is less than the prescribed weight a command step  360  will instruct the control module to suppress the passenger side air bag. In addition, and in applications where the alternative seat belt pre-tensioners (P/T)  328  have been included these will also be suppressed by command step  360 .  
         [0075]    If on the other hand, decision node  358  determines that the occupant is not less than the prescribed weight a command step  362  instructs the control module to deploy the passenger side air bag as well as seat belt pre-tensioners (P/T)  328  if, of course, the same are included in the system.  
         [0076]    Referring now to FIGS.  12 - 15 , an embodiment of a seat belt tension sensor is shown generally at  410 . Seat belt tension sensor  410  includes an analog sensor design, which will produce a signal relative to the variation in the tension of the seat belt. Seat belt tension sensor  410  has a housing portion  412 . Housing portion  412  is preferably constructed out of a lightweight, easily-molded material such as plastic. Housing  412  has a central receiving area  414 . A slider  416  is configured to be slidably received within central receiving area  414 .  
         [0077]    The dimensions of slider  416  are such that the same is capable of movement in a range defined by a first position (FIG. 12) and a second position (FIG. 13). The first position corresponds to liffle or no tension, and the second position corresponds to a tension greater than or equal to a predetermined tension. The predetermined tension relates to a tension value that will determine whether or not a child seat is cinched by the seat belt.  
         [0078]    Housing  412  has an opening  418 . In addition, slider  416  has an opening  420 . Opening  418  is larger than opening  420 , allowing opening  420  to traverse within opening  418  as slider moves within the range defined by the first position and the second position. In addition, slider  416  has a pair of tab portions  422  which protrude outwardly from the surface of slider  416  proximate to opening  420 .  
         [0079]    A sensor  424  is also positioned within receiving area  414 . In an exemplary embodiment, sensor  424  is a Hall effect sensor assembly. Hall effect sensor assembly  424  includes a Hall effect device and complimentary circuit board  425 . An opening  426  is disposed on slider  416 . Opening  426  is substantially large enough to allow slider  416  to move within the range defined by the first position and the second position, while Hall effect sensor assembly  424  remains stationary. In addition, slider  416  is configured to have a shoulder portion  428 . Shoulder portion  428  is configured to accommodate a baseplate  430  to which Hall effect sensor  424  and related electrical components are secured. As illustrated in FIGS.  12 - 15 , Hall effect sensor  424  depends outwardly from baseplate  430 . Accordingly, the securement of Hall effect sensor  424  within receiving area  414  will not impede the travel of slider  416 .  
         [0080]    A pair of magnets  432  and  434  are positioned at either end of opening  426 . Accordingly, and as slider moves in the range defined by the first position (FIG. 12) and the second position (FIG. 13), hall effect sensor  424  moves away from magnet  432  and travels toward magnet  434 .  
         [0081]    The Hall effect device will sense the strength of the magnetic field of the approaching magnet (either magnet  432  or magnet  434 , depending on the direction of travel), and depending on the strength of the magnetic field, the Hall effect device will generate an electric signal to determine the level of the tension force, the electric signal being received by a system controller to determine whether or not to suppress any safety-related items such as a hypertensioner, airbag, or pre-tensioner, etc. When the tension force exceeds the pre determined threshold, the system will suppress a passenger air bag. The analog design will provide a liner output, corresponding to seat belt tension, to the controller.  
         [0082]    In an exemplary embodiment, the Vcc of the Hall effect sensor assembly  24  is 5 volts +/−0.5 volts DC. The voltage with no magnetic field present will be approximately 2.5 v. As the magnet is brought into the proximity of the sensor, the voltage will increase to near Vcc or decrease to near ground, depending on the polarity of the magnet. Accordingly, as the voltage increases or decreases, so does the tension of the seat belt. Of course, Vcc may have values greater than and less than 5 volts.  
         [0083]    A biasing force for urging slider  416  in the direction of the first position (FIG. 12) is provided by a plurality of springs  436 . Plurality of springs  436  are configured to be received within a plurality of spring apertures  438  in slider  416  at one end, and make contact with a wall  440  of receiving area  414 . In an exemplary embodiment, three springs are used, and as applications may require, the number, size, and configuration of springs  436  may vary.  
         [0084]    Once the internal components of sensor  410  are assembled, an anchor plate  442  is secured to housing  412 . In an exemplary embodiment, anchor plate  442  is manufactured out of a durable material such as steel. Anchor plate  442  has an opening  444  which aligns with opening  418  of housing  412  when anchor plate  442  is secured to housing  412 . Opening  444  is substantially similar to opening  418  of housing  414 , thus allowing the travel of opening  420  within openings  444  and  418 .  
         [0085]    Anchor plate  442  has a securement end  446  which is configured to engage a shoulder portion  448  of housing  412 . In addition, anchor plate  442  has a securement opening  450 , positioned to engage a securement tab  452  of housing  412 . A securement tab  452  is molded into housing  414  and includes a chamfered engagement surface  454  and an engagement surface  456 . Accordingly, and since securement tab  452  is molded out of the same material of housing  414 , securement tab  452  has resilient qualities which allow it to have a snap fit engagement of anchor plate  442  to housing  412 . Accordingly, seat belt tension sensor  410  is easily assembled by snapping anchor portion  442  to housing  412 . Accordingly, there are no additional manufacturing steps.  
         [0086]    Anchor plate  442  has a securement portion  458  which depends away from housing  414  when anchor plate  442  is secured to the same. Securement portion  458  has an opening  460  which allows a securement bolt to pass therethrough in order to secure sensor assembly  410  to a vehicle.  
         [0087]    Referring now to FIGS.  12 - 15 , and as sensor assembly  410  is fixedly secured to a vehicle, a portion of a seat belt  462  passes through openings  418 ,  420 , and  444 . Referring now to FIGS. 12 and 13, a plurality of springs  436  provide an urging force in the direction of arrow  464  to maintain slider in the position illustrated in FIG. 12. In an exemplary embodiment, the biasing force of springs  436  is overcome when a force in the amount of 5 to 15 lbs is applied in the direction substantially opposite of arrow  464 . Of course, and as applications may require, the biasing force of springs  436  to be overcome may vary. For example the biasing force of springs  436  may be greater or less than 15 lbs, this can be varied to comply with a manufacturing request for a different biasing force. Accordingly, and when the urging force of springs  436  is overcome, slider  416  travels towards the position illustrated in FIG. 13. In so doing, magnet  432  is moved away from the Hall effect sensor and magnet  434  is moved closer to the Hall effect sensor, causing a resulting signal to be sent through one of a plurality of wires  466  secured to Hall effect sensor  424 .  
         [0088]    The signal is ultimately received by a microcontroller  468  which controls the operation of an occupant protection system(s)  470  such as an airbag or other safety restraint system. The microcontroller will suppress the air bag and provide a signal to an indicator light  472  to indicate that the air bag has been suppressed. Indicator light  472  is located in a position within the vehicle compartment that is easily viewed by the operator and/or occupants of the same. For example, one such location of indicator light  472  is on the vehicle dashboard. In addition, the microcontroller may also provide an audible tone or voice response, indicating that the air bag has been suppressed.  
         [0089]    Referring now to FIGS. 16 and 17, alternative design configurations of sensor  410  are illustrated. In FIG. 16, a plurality of protrusions  474  are positioned to receive one end of springs  436 . In FIG. 17, springs  436  are received within a central spring aperture  438 . In addition, securement end  446  of anchor plate  442  can be configured to have an angular displacement with respect to anchor plate  442  (FIG. 16). Alternatively, securement end  446  of anchor plate  442  depends outwardly from the same.  
         [0090]    Referring now to FIGS. 18 and 19, an alternative embodiment of the present invention is illustrated. Here, component parts performing similar or analogous functions are labeled in multiples of  500 . Here, seat belt tension sensor  510  is a digital sensor design. This design is configured to provide an On-Off signal to the controller in order to suppress the safety device.  
         [0091]    Here, slider  516  is configured to have a receiving area  580  having a plurality of tabs  582  for engaging notches  584  in a shutter  586 . Shutter  586  is a planar member constructed out of a metal capable of shunting the magnetic field generated by a magnet  532 .  
         [0092]    In this embodiment, a single magnet  532  is positioned to be sensed by a Hall effect sensor assembly  524 . Accordingly, and as slider  516  is urged by the tension of the seat belt passing through seat belt tension sensor  510 , shutter  586  is moved away from its shunting position in between the hall effect sensor and the magnet. The movement of shutter  586  away from magnet  532  is detected by Hall effect sensor assembly  524  and a signal is sent out to a microcontroller via wires  588 .  
         [0093]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.