Abstract:
A seatbelt retractor inertial locking system for motor vehicle belt restraint systems. The inertial locking system incorporates features to reduce the influence of contaminants from causing unwanted locking of the associated retractor. The feature is in part provided by the positioning of a point contact between a ball mass and a locking lever. The inertia actuator forms the inertial ball mass nest surface which has a vented construction which permits the escape of contaminants and further contributes to reducing noise generated by contact between the ball mass and the nest surface.

Description:
FIELD OF THE INVENTION 
     This invention relates to an automotive occupant restraint seat belt retractor, and particularly to an inertial sensor of a vehicle sensitive control system for such a retractor. 
     BACKGROUND OF THE INVENTION 
     Motor vehicles are frequently equipped with active occupant restraint systems such as seat belt assemblies. Seat belt assemblies typically have lap and shoulder belt portions for restraining the occupant in the event of an impact or rollover event. To enhance the comfort and convenience provided by the seat belt system and to provide other functions, retractors are provided which allow the belt webbing to be freely paid-out and retracted when the vehicle is not subjected to unusual acceleration forces or inclination. In the event of exposure to such forces, a retractor control system activates to lock the retractor to prevent additional pay-out (extraction or protraction) of webbing. Thus, the retractor locks in a manner to enable the seat belt webbing to restrain the occupant. Such retractor control systems take various forms. One category of such control systems is known as vehicle sensitive inertial locking systems. These systems are sensitive to acceleration forces acting on the vehicle resulting from a frontal impact, side impact, rollover, and when certain other forces act on the vehicle. 
     Another category of such retractor control systems is known as belt sensitive control systems. These devices operate much in the manner of a centrifugal clutch and sense the rotational speed of the retractor spool, such that when high angular accelerations of the retractor spool occurs associated with rapid extraction of webbing, the control system engages to lock the retractor. This invention is related to an improved vehicle sensitive retractor inertial locking sensor. 
     As mentioned previously, vehicle sensitive retractor inertial locking sensors must respond to acceleration loads acting in various axes and planes. Primarily important are impacts to the vehicle creating acceleration loads acting in the horizontal plane, such as front, rear, or side impact conditions. However, if a rollover event has occurred, it is important that the retractor lock to restrain the occupant. Typical inertial retractor locking sensors utilize a pendulum, standing man, or rolling ball type inertial mass to activate a locking lever which engages directly or indirectly with a ratchet wheel of the retractor webbing spool which acts as a spool lock. In response to accelerations of the vehicle, the inertial mass moves to urge the locking lever to engage with the ratchet wheel, thus locking the spool from allowing further extraction of webbing. These devices have been utilized for many decades and have proven to be reliable and effective retractor control systems. 
     In the operating environment of a passenger car, interior components are subjected to exposure to foreign material such as liquids, dirt, and particles associated with normal or expected use of the vehicle by its occupants. The presence of foreign objects infiltrating into a seat belt retractor mechanism can interfere with operation of an inertia sensitive sensor. Traditional inertial sensors using a rolling ball or standing man type inertial mass can operate improperly in the event that debris remains in contact with the inertial mass or the related components which can interfere with desired lock-up operation of the system. For example, in the case of a rolling ball type mass, foreign particles collecting on the ball mass can become interposed between the ball mass and the associated ball seat, or between the ball mass and the associated actuating lever which senses movement of the ball. The presence of such contaminants can interfere with the designed system tolerances and interaction between actuation components. Moreover, due to the typical manner of providing a sensing lever acted on by a ball mass, very small sized contaminants can produce significant movement of the lever which can lead to inadvertent lock-up behavior. The precision requirements of present designs impose manufacturing cost penalties and capacity constraints. 
     In one prior art design of a ball mass type inertial sensor, the actuation lever forms a ring which contacts the ball mass along a ring contact line on an upper surface of the ball. As soon as the ball mass starts to move in any direction, the lever begins to lift due to contact with the ring feature. Even normal lever-to-housing parts tolerance variations may cause the lever to begin to lift (from a desired nominal position) and reduce the gap with the associated ratchet wheel, perhaps leading to inducing lockup when the system is not affected by movement/acceleration. This condition leads to an unintentionally sensitive retractor assembly. 
     Another important consideration in the design and manufacture of automotive components is their tendency to contribute to unwanted noise during vehicle operation referred to generally as buzz, squeak, and rattle (BSR). Existing vehicle sensitive inertia sensors have tendencies to create undesirable noise as the inertial mass moves within its seat and against the associated locking lever and other components. 
     In view of the above, there is a desire in the design of retractor inertial actuators to improve their tolerance to contaminants and further to provide means for eliminating contaminants which can lead to the above-described improper operation. In addition, there is a need to provide retractor inertial actuators which reduce BSR problems. 
     SUMMARY OF THE INVENTION 
     In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a vehicle sensitive retractor inertial locking sensor having a point of interaction between a spherical ball mass and its associated actuating lever which is spaced some distance from the axis of pivoting motion of the actuating lever, as compared with conventional designs. This point contact results in a reduced angular deflection of the actuating lever caused by the presence of a given size of contaminant particle at the contact area between the ball mass and the actuating lever as compared with prior art designs. The inertial locking system of this invention further provides an inertial ball seat design featuring a vented construction which aids in allowing contaminants to fall away from the actuator, and further provides a damping function to reduce noise resulting from vibration of the inertial ball mass. 
     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial view of a seat belt retractor inertial locking actuator in accordance with the present invention; 
         FIG. 2  is a side sectional view of the seat belt retractor locking actuator as illustrated in  FIG. 1  shows further shown with components of a retractor spool; 
         FIG. 3  is an enlarged cross-sectional view of the actuator shown in  FIG. 2 ; 
         FIG. 4  is a pictorial view of the inertial locking actuator showing the locking lever and ball mass removed; and 
         FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A seat belt retractor inertial locking sensor in accordance with the present invention is illustrated in  FIGS. 1 and 2  and is generally designated by reference number  10 . Locking sensor  10  operates in conjunction with a ratchet wheel  12  which is part of a seat belt retractor (not shown in its entirety) having a rotating webbing spool. Ratchet wheel  12  includes an array of ramped teeth  14  around its perimeter. Teeth  14  are used to enable locking sensor  10  to lock the webbing retractor spool, restricting extraction of seat belt webbing under specific operating conditions. Locking sensor  10  primarily incorporates locking lever  16 , ball mass  18 , and housing  22  forming ball nest  20 . 
     It should be recognized that various approaches for providing a spool lock of a retractor locking system are known. Due to the extremely high forces involved in the locking operation of a retractor in restraining impact loads acting on seat belt webbing, ratchet wheel  12  may act as an intermediate locking device for the associated retractor. Locking lever  16  may force a pivoting locking bar (not shown) into engagement with spool ratchet wheel  12 . In other words, the high torque loads acting on a retractor spool during occupant restraint may not, in some forms of the invention, be directly restrained by the interaction between arm edge  28  and ratchet wheel  12 . Conventionally known mechanical servo-type spool lock engagement systems can be used for retractor inertial sensitive locking systems, such as that of the present invention. These systems allow the highly sensitive inertia locking sensor  10  to actuate other elements of a spool lock mechanism to lock the spool with sufficiently high strength to sustain restraint loads. These features are conventionally known and outside the scope of the novel features of the present invention. 
     Locking lever  16  is rotatably supported for pivoting motion about a shaft  23  which defines a pivot axis  24  (best shown in  FIG. 3 ). Locking lever  16  includes arm  26  which forms edge  28  which engages with ratchet wheel teeth  14  under specific operating conditions, as briefly described above and explained in more detail in the following description. Lever  16  extends over the upper surface of ball mass  18  and includes a ring-shaped rim  30 . Rim  30  is annular, encircling the upper surface of ball mass  18  but its surface is displaced from contact with the ball mass while it is in its normal position, like a halo. Accordingly, in the normal position of ball mass  18  there is clearance between the ball mass and rim  30 . The center of gravity  38  (cg) of lever  16  is positioned relative to pivot axis  24  such that the locking lever is normally urged to rotate in the counterclockwise direction (when viewing the lever as in  FIG. 3 ) such that the lever is urged downwardly into contact with ball mass  18 . 
     As best shown in  FIG. 3 , locking lever  16  contacts ball mass  18  when it is in its normal resting position as shown in the figure at a point contact  32 , which is positioned along or adjacent to the vertical diametric plane  50  of ball mass  18 . Plane  50  is vertical with respect to gravity when sensor  10  is in its mounted position within the associated motor vehicle. This point contact  32  creates an actuating lever arm length  34  as shown in  FIG. 3 . For reasons which will be described in more detail as follows, the positioning of point contact  32  contributes to the debris tolerance capabilities of locking sensor  10 . 
     Ball mass  18  rests on ball nest  20  which forms a generally concave surface on which the ball mass is cradled to remain in its normal position shown in  FIG. 3 . This positioning of the components is associated with the normal condition of the components of the locking sensor  10  in which inertial loads are not acting on the associated vehicle and retractor locking is not desired. In this position, the cg position  38  of locking lever  16  maintains it in the position shown in  FIG. 3 , in which arm edge  28  does not engage with ratchet wheel  12 . 
     Operation of control sensor  10  in various conditions will now be described with reference to the Figures. As mentioned previously,  FIG. 3  illustrates the orientation of the components in the normal condition in which inertial forces are not acting on the locking sensor  10  and locking of the associated retractor is not desired. In this condition, locking of the retractor does not occur since arm edge  28  does not engage with ratchet wheel  12  which acts as a spool lock. When inertial forces are acting on locking sensor  10  in a horizontal plane (corresponding to longitudinal or lateral inertial forces on the vehicle), ball mass  18  is urged to move from its normal position to a displaced actuation position.  FIG. 3  shows an example of such displacement of ball mass  18  in phantom lines. In such an actuation, ball mass  18 , through its contact with lever  16  at point contact  32 , urges the locking lever to rotate clockwise about axis  24  to a position in which edge  28  engages with ratchet wheel  12 , causing the associated retractor to lock. 
     In conventional inertial actuators, it is common for rim  30  to be the initial contact surface between locking lever  16  and ball mass  18 , thus forming a ring contact line. In a condition where debris is present and interposed between ball mass  18  and locking lever  16 , a contaminant particle of a given size causes a greater clockwise rotation of locking lever  16  as the interaction point between lever  16  and ball mass  18  moves closest to pivot axis  24 . In other words, a contaminant interposed between ball mass  18  and the right-hand region of rim  30  designated as area  40  causes a greater angular displacement of the locking lever than the same contaminant interposed between the ball mass and the lever at point contact  32  in accordance with the present invention. By moving the contact area to near the vertical diametric plane  50  of ball mass  18 , the tolerance to the presence of contaminants which may become lodged between the ball mass and lever  16  is enhanced. As mentioned previously, tolerance to the presence of contaminants is an important design objective of devices in accordance with the present invention. In addition to the debris tolerance, the inertial locking system  10  of the present invention allows a small “mismatch” between locking lever  16  and ball mass  18  to occur without lifting the lever and reducing the pawl gap (spacing between edge  28  and ratchet wheel teeth  14 ) to exist without causing the potential for an oversensitive retractor or locking too early. 
     When ball mass  18  moves to one of its displaced position as illustrated in phantom lines in  FIG. 3 , rim  30  engages the ball mass to aid in rotating locking lever  16  to the locking position. This may occur with any portion of rim  30 , including displacement of the ball mass in the right-hand direction (as the components are shown in  FIG. 3 ) to engage with rim  30  at area  40 . However, in the normal position of ball mass  18  however, there is a separation between rim  30  and the surface of the ball mass. 
       FIG. 4  illustrates additional features of locking sensor  10  which aid in providing two benefits; namely, contaminant tolerance and reduction of noise. Nest surface  39  forms a number of apertures including central aperture  42  formed by ring section  43  and V-shaped slots  44  which form a number of radially projecting ribs  46  extending from central aperture  42  to the outer perimeter of ball nest  20 . The V-shaped slots  44  also define inwardly extending pointed extensions  48 . V-shaped slots  44 , ribs  46 , and extensions  48  act to disrupt the transmission of vibrations caused by contact between ball mass  18  and surface of the ball nest  20 , or the transmission of vibrations to the ball mass. These features tend to reduce the creation and transmission of noise upon such vibrations since they tend to reduce the presence of a continuous transmission path through housing  22  along nest  20  conducting vibrational movement which produces sound. The clear openings provided by V-slots  44  and central aperture  42  further provide an escape path for contaminants that may be present in the area of ball mass  18 . This enables the contaminants to fall under the force of gravity past and underneath ball mass  38  where they will not interfere with operation of locking sensor  10 . 
     While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.