Abstract:
A one-way locking assembly having an axially moveable member extending through a locking structure. The locking structure including an engagement member contacting an exterior surface of the axially moveable member and being movable relative to the exterior surface of the moveable member in a first direction while being substantially immovable along the outer surface of the moveable member in a direction opposite to the first direction. The engagement member further including a pair of lock arms extending radially inward from a circumferential frame and terminating in distal ends engaging the exterior surface of the moveable member.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional patent application No. 61/794,134, filed on Mar. 15, 2013, the entire contents of which are herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to seatbelt restraint systems for motor vehicles. More particularly, the present invention relates to a locking mechanism for a linear pretensioner of a seatbelt restraint system in a motor vehicle. 
         [0004]    2. Related Technology 
         [0005]    Seatbelt restraint systems used for restraining occupants in motor vehicle seats play an important role in reducing injury to the occupants in the unfortunate event of a vehicle crash. While there are several varieties of seatbelt restraint systems, the conventional “3-point” variety has a lap belt section extending across the pelvis and a shoulder belt section crossing the upper torso of a seated occupant. The lap and shoulder belt sections are each connected to the vehicle structure by anchorages and may be further fastened to each other or formed as portions of a continuous length of seatbelt webbing. Seatbelt restraint systems that are manually secured by the occupant (“active” types) also typically include a latch plate attached to the belt webbing. Such a system further includes a seatbelt buckle attached to the vehicle body structure by another anchorage. The latch plate is received by the buckle thereby allowing the seatbelt restraint system to be fastened, enabling restraint, and unfastened, allowing entrance and exit from the vehicle. Of the anchorages securing the lap and shoulder belt sections, one anchorage typically includes a belt retractor to store the belt webbing. This belt retractor may further act to manage belt tension loads during a crash situation. Seatbelt restraint systems, when deployed, effectively restrain the occupant during a collision. 
         [0006]    OEM (Original Equipment Manufacturer) vehicle manufacturers often provide seatbelt restraint systems with pretensioning devices (usually referred to just as a “pretensioner”). These devices induce tension in the seatbelt, either prior to impact of the vehicle during a collision or at an early stage of a sensed impact/collision, so as to enhance occupant restraint performance. This pretensioning takes slack out of the webbing and permits the seatbelt restraint system to engage the occupant earlier in the crash sequence. 
         [0007]    One class of pretensioning devices is a pyrotechnic linear pretensioner (PLP). A PLP can be implemented as a pyrotechnic buckle pretensioner (PBP) that is attached to and activated through the seatbelt buckle. In other implementations, the PLP can be attached to a webbing guide loop, either anchorage connected to the opposing ends of the seatbelt webbing or directly to the webbing itself. Since all of the above types of pretensioners linearly pull a seatbelt system component to induce tension in the seatbelt webbing, they are collectively referred to as PLPs. 
         [0008]    When a collision occurs, a pyrotechnic charge in the PLP is fired, producing an expanding gas that pressurizes a gas chamber. This pressure forces a piston to move. The piston is connected with the belt system by a cable, a strap or the webbing of the restrain system, and the stroking of the piston tightens or “pretensions” the belt against the occupant. Various examples of PLP and PBP designs are provided in U.S. Pat. Nos. 6,068,664 and 7,823,924, which are hereby incorporated by reference. 
         [0009]    Designers of automotive components are constantly striving to reduce the mass of the components as part of the overall goal of providing higher fuel efficiency for motor vehicles. Additionally, these same designers are also constantly striving to reduce costs in automotive components. One way to achieve the above is to reduce packaging or sizing of components. 
         [0010]    In accordance with one known design approach, the PLP includes a machined or die cast piston that is sealingly coupled to a tubular combustion cylinder. When activated, relative movement between the combustion cylinder and the piston occurs, with the combustion cylinder being extended out of the piston. The belt webbing is wound around an actuating profile defined on an end of the combustion cylinder, opposite of the piston, such that the length of the belt webbing is shortened by a distance corresponding to twice the distance of the mechanism&#39;s stroke. This doubling of the effect of the mechanism&#39;s stroke on the belt webbing enables the overall length of the PLP packaging to be shortened. 
         [0011]    As the occupant begins to load the seatbelt webbing during an impact, the forces urge the reverse movement of the combustion cylinder relative to the piston, in other words the cylinder is urged back into the piston. Such a reversal of the relative movement of the piston and combustion cylinder is undesirable since it induces slack in the belt webbing and increases the momentum and movement of the occupant and, therefore, the potential risk to the occupant. 
         [0012]    A method of limiting this reversal of movement is to provide a one-way clutch assembly associated with the piston assembly. One style of a one-way clutch includes conical and annular portions of the piston head as part of the clutch. In such a system, the piston is movable within a combustion cylinder and the components forming the clutch are located between a pair of piston heads traversing within that cylinder. Movement in the playback direction wedges BBs, retained between the heads of the piston, between the conical portion and the inner surface of the combustion cylinder. This wedging of the BBs results in locking of the piston. 
         [0013]    The construction of the above system is complex and labor-intensive during manufacturing. A simplify construction for the one-way clutch would be beneficial in that it would reduce weight and packaging requirements as well as reduce labor intensity during manufacturing. 
       SUMMARY 
       [0014]    In satisfying the above needs, as well as overcoming the enumerated drawbacks and other limitations of the related art, in one aspect the present invention provides a pretensioner for a motor vehicle belt restraint system having a base plate defining a length and a combustion sub-assembly fixedly mounted to the base plate. The sub-assembly includes a combustion cylinder and a combustion housing, the latter of which defines a combustion chamber and retains a gas generator in communication with the combustion chamber. The combustion cylinder extends from the combustion housing in a direction along the length of the base plate. An interior passageway of the cylinder is in fluid communication with the combustion chamber, whereby an expanding gas generated by the gas generator is transmitted through the interior passageway of the combustion cylinder. A piston is movably mounted to the base plate and has closed ended bore within which at least a portion of the combustion cylinder is received. The closed ended bore is in fluid communication with the interior passageway of the combustion cylinder, and the piston is movable along the combustion cylinder in response to generation of the expanding gas. A one-way locking structure is supported by the piston and movable therewith. The locking structure includes an engagement member contacting an exterior surface of the combustion cylinder. The engagement member is movable along the exterior surface of the combustion cylinder in a first direction and is substantially immovable along the outer surface of the combustion cylinder in a direction opposite to the first direction. 
         [0015]    In another aspect of the invention, the engagement member is one of a deflectable arm or a BB. 
         [0016]    An additional aspect of the invention, the one-way locking structure is disposed about the combustion cylinder. 
         [0017]    In a further aspect of the invention, the one-way locking structure is of a one-piece construction. 
         [0018]    In yet another aspect of the invention, the one-way locking structure is planar. 
         [0019]    In still a further aspect of the invention, the one-way locking structure includes a frame defining a perimeter of the one-way locking structure, a pair of opposed lock arms extending radially inward from the frame. 
         [0020]    In an additional aspect of the invention, the one-way locking structure includes a lock piece having a pair of lock arms extending radially inward and terminating in distal ends engaging the outer surface of the combustion cylinder. 
         [0021]    In another aspect of the invention, the distal ends of the lock arms define semicircular end faces. 
         [0022]    In yet another aspect of the invention, each of the semicircular end faces defines an included angle that is less than 180°. 
         [0023]    In a further aspect of the invention, the end faces are obliquely oriented with respect to a plane defined by the lock arms. 
         [0024]    An additional aspect of the invention, the lock arms are obliquely oriented with respect to the combustion cylinder. 
         [0025]    In still another aspect of the invention, the lock arms are disposed in the direction toward the combustion housing. 
         [0026]    In a further aspect of the invention, the one-way lock structure includes a collar disposed about the combustion cylinder, the collar further having a passageway defined therethrough the passageway being formed by a conical surface. 
         [0027]    In a still further aspect of the invention, a series of BBs are disposed between the conical surface of the collar and the exterior surface of the combustion cylinder. 
         [0028]    An additional aspect of the invention, the conical surface is narrower on a side of the collar adjacent to the piston and is wider on a side of the collar located toward the combustion housing. 
         [0029]    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 
         [0030]      FIG. 1  is perspective view of a pretensioner, in accordance with the principles of the present invention, showing the pretensioner in a pre-activation position; 
           [0031]      FIG. 2  is perspective view of the pretensioner seen in  FIG. 1 , with the seatbelt webbing removed and showing the piston in a post-activation position; 
           [0032]      FIG. 3  is a sectional view, generally taken along line  3 - 3 , of the pretensioner seen in  FIG. 2 ; 
           [0033]      FIG. 4  is a plan view of one embodiment of a lock piece utilized in connection with the pretensioner seen in  FIGS. 1-3 ; 
           [0034]      FIG. 5  is a cross-sectional view, generally taken along line  5 - 5 , of the lock piece seen in  FIG. 4 ; 
           [0035]      FIG. 6  is an enlarged perspective view of an alternative one-way clutch assembly incorporated into a pretensioner in accordance with the principles of the present invention; and 
           [0036]      FIG. 7  is a partial sectional view through  FIG. 6  illustrating the working details of the one-way clutch assembly shown therein. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    A representative seatbelt restraint system that may be used with a pretensioner incorporating principles of the present invention generally includes a seatbelt that is mounted to a body structure of the motor vehicle. One end of the seatbelt is preferably connected to a retractor that operates to retract the seatbelt, both when in use and when not in use. The seatbelt includes a lap belt section and a shoulder belt section. The lap belt section, when deployed, extends across the pelvic region of an occupant sitting on the seat of the motor vehicle. The shoulder belt section extends laterally across the upper torso region of the occupant. The lap belt section and the shoulder belt section may be joined together at a respective end of each section or be provided as portions of continuous seatbelt webbing. 
         [0038]    Provided on the seatbelt is a latch plate, which may be slidable along at least a portion of the length of the seatbelt. When the seatbelt is deployed, the latch plate generally defines the transition between the lap belt section and the shoulder belt section. 
         [0039]    The seatbelt restraint system also includes a buckle located relative to one side of the seat. Like the seatbelt, the buckle is secured to a body structure of the vehicle. The previously mentioned latch plate is removably secured within the buckle, such that when the latch plate is engaged with the buckle, the retractor provides for retraction of the seatbelt gently against the body of the occupant. When the latch plate is released from the buckle, the retractor provides for full retraction of the seatbelt so that the seatbelt will not inhibit the ingress and egress of the occupant into and out of the vehicle. 
         [0040]    To assist in controlling movement of the seatbelt, a guide loop is usually fixed to a vehicle door pillar, such as the B-pillar, or to the seat at approximately the shoulder height of the occupant. In some installations, the position of the guide loop may be vertically adjustable. The guide loop thus positions shoulder belt section diagonally across the torso, the shoulder, chest and abdomen, of a seated occupant and re-directs it back toward the retractor. 
         [0041]    The seatbelt restraint system also includes a linear pretensioner, which is illustrated in  FIG. 1  and generally designated at  10 . As its primary components, the linear pretensioner  10  includes a frame  12 , and a pyrotechnically driven piston assembly  14 , which includes a combustion sub-assembly  15  and a piston or reaction housing  16 . By way of the present invention, the piston assembly  14  interacts with the seatbelt webbing  18  of the seatbelt restraint system to induce tension in the webbing  18 , thereby reducing the momentum that can be generated by an occupant during an impact or crash. 
         [0042]    The frame  12  of the pretensioner  10  has a base plate  20  formed of sheet metal with a profile that is L-shaped, the L-shape having a long leg  22  extending in the axial direction and a short leg  24  extending in a transverse direction to the long leg  22  at one end. Extending along the length of the long leg  22 , generally perpendicularly thereto, and along the length thereof, is a pair of opposed rolled or bent side walls  26 . The sidewalls  26  are used as securements for the reaction housing  16 , which is further discussed below. 
         [0043]    The combustion sub-assembly  15  includes a combustion head  30  and a combustion cylinder  32 , both of which are slideably mounted to the frame  12 . While the combustion head  30  and the combustion cylinder  32  are slideably mounted to the frame  12 , the reaction housing  16  is fixedly mounted to the frame  12 . The reaction housing  16  and the combustion head/cylinder  30 ,  32  are thus moveable relative to one another. 
         [0044]    The combustion head  30  is retained to and supported by a pair of end flanges  36  having feet  38  located at lower sides thereof. To secure the flanges  36  and, therefore, the combustion head  30  to the frame  12 , the feet  38  are retainingly engaged between a pair of opposed or rolled side walls  40 , which like the side walls  26 , extend upwardly from the lateral sides of the base plate  20 . The side walls  40 , however, define a race  28  that retains the feet  38 , but does not fixedly secure them to the base plate  20 . The feet  38  are therefore free to slide along the side walls  40  and within the race  28 . As seen in  FIG. 1 , one of the rolled side walls  40 , the lower side wall  40  in the figure, is shown cut-away to reveal one of the feet  38  of the combustion head  30 . 
         [0045]    Between the end flanges  36 , the body of the combustion head  30  internally defines a combustion chamber  42  (shown in  FIG. 3 ), and coupled to the combustion chamber  42  is a micro-gas generator  44 . Since micro-gas generators are well known in the field of pretensioners, further details on the construction and operation of the micro-gas generator  44  are omitted herein. While the micro-gas generator  44  may be coupled to the combustion chamber  42  in a variety of ways, as illustrated it is provided within a tubular extension  46 , extending from the body of the combustion head  30 , laterally through or from one of the end flanges  36 . 
         [0046]    The combustion cylinder  32  is fixedly mounted to the combustion head  30  by way of a bore  47 . The bore  47  extends through the combustion head  30  and provides a means by which a combustion passageway  33 , defined within the combustion cylinder  32 , communicates with the combustion chamber  42 . 
         [0047]    The combustion cylinder  32  extends from the combustion head  30  generally axially along the frame  12  and is supported at one end by the combustion head  30  and at its opposing end by the reaction housing  16 , within which it is slidingly received. To facilitate receiving of the end of the combustion cylinder  32  within the reaction housing  16 , the reaction housing  16  includes an internal bore  48 . 
         [0048]    In its pre-activated state, the reaction housing  16  is located adjacent to the combustion head  30 , and the combustion cylinder  32  is substantially completely received within the bore  48  of the reaction housing  16 . During activation, a firing signal is provided to the micro-gas generator  44  by way of firing leads (not shown). In response to the firing signal, the micro-gas generator  44  ignites and an expanding gas is released into the combustion chamber  42 . From the combustion chamber, the expanding gas proceeds through the passageway  33  of the combustion cylinder  32  and into the internal bore  48  of the reaction housing  16 . As previously noted, the reaction housing  16  is fixedly secured to the frame  12 . To facilitate this securement to the frame  12 , the reaction housing  16  may have feet  52  formed on its lateral lower sides that are received beneath the rolled over portion of the side wall  26  and clamped or compressively engaged between the sidewalls  26  of the base plate  20 . 
         [0049]    As the expanding combustion gas enters into the internal bore  48  of the reaction housing  16 , the gas exerts a force urging the combustion head  30  to move away from the reaction housing  16 , away from the short end  24  of the frame  12 . To prevent combustion gas from escaping or leaking out of the internal bore  48  of the reaction housing  16  past the combustion cylinder  32 , the end of the combustion cylinder  32  is formed with a sealing head  54 , which may include an elastomeric seal  56 , such as an O-ring, received within an annular groove  58 . In this regard, attention is directed to the construction shown in  FIG. 3 . 
         [0050]    The pretensioner  10  induces tension in the seatbelt webbing  18  because an end of the seatbelt webbing  18  is extended about an activation profile  60  defined at the end of the combustion head  30 . The activation profile  60  redirects the seatbelt webbing  18  by an angle in the range of 160° to 180°, nearly in an opposite direction from which it was received. The end of the webbing  18  is thereafter secured to the base plate  20  of the frame  12 . By extending the seatbelt webbing  18  around the activation profile  60 , the distance that the seatbelt webbing  18  is moved during activation of the reaction housing  16  is effectively two times the maximum stroke length of the combustion head  30 . With this doubling effect, the pretensioner  10  is able to have a reduced overall length. The positioning of the seatbelt webbing  18  about the activation profile  60  of the combustion head  30  is shown in  FIG. 1 , wherein portions of the seatbelt webbing  18  are partially cut-away to reveal additional components of the pretensioner  10 . 
         [0051]    The movement of the combustion head  30  under the urging of the expanding combustion gas is opposed by a pulling force P or resistance exerted by the seatbelt webbing  18 . At some point, the opposing force on the combustion head  30  may be strong enough that the combustion head  30  is unable to further pull the webbing  18  in the activation direction A. As the occupant begins to load the seatbelt webbing  18  during a collision, the pulling force P will urge the combustion head  30  to move in a direction opposite of the activation direction A, which is herein referred to as the playback direction. To prevent this, the pretensioner  10  includes a lock piece  62  that is actuated upon movement of the combustion head  30 , and more specifically the combustion cylinder  32 , in the playback direction. 
         [0052]    The lock piece  62  is mounted to an end face  64  of the reaction housing  16  that is generally positioned opposite of the combustion head  30 . Mounting of the lock piece  62  to the end face  64  can be achieved by any known means including mechanical fastening or adhesive fastening thereto. Operation of the lock piece  62  utilizes the combustion cylinder  32  as a lock bar and prevents back driving of the combustion head  30  towards the reaction housing  16 . 
         [0053]    Referring now to  FIGS. 4 and 5 , the lock piece  62  is generally a planar structure having a frame  66  within which are provided a pair of opposed locking arms  68 . The frame  66  is has a rectangular shape that is dimensioned to correspond with the shape of the end face  64  of the reaction housing  16 . While shown as corresponding in size and shape to the end face  64  the reaction housing  16 , the frame  66  and the lock piece  62  may exhibit a size/shape that is larger or smaller and different than the end face  64 , so long as the lock piece  62  does not interfere with movement of the combustion cylinder  32  and combustion housing  30  in the activation direction A. 
         [0054]    The frame  66  includes longitudinal parts  70  between which extend lateral end parts  72 . The locking arms  68  are provided between the longitudinal parts  70  and extend toward one another from the end parts  72  and terminate at distal ends  74 , which are provided with a semicircular shape that corresponds in part with the outer surface of the combustion cylinder  32 . The length of the lock arms  68  from the end parts  72  to the distal ends  74  is greater than the length from the end parts  72  to the outer surface of the combustion cylinder  32 . For this reason, the semicircular shape of the distal ends  74  forms less than a full half-circle and the lock arms  68  engage the combustion cylinder  32  at an oblique angle. More specifically, when contacting the outer surface of the combustion cylinder, the lock arms  68  are generally disposed toward the combustion head  30 . Additionally, the end faces  76  are oblique to the plane of the lock arms  68 , as best seen in  FIG. 5 . The oblique orientation of the end faces  76  allows the end faces  76  to be positioned in surface-to-surface contact with the outer surface of the combustion cylinder  32  when the combustion cylinder  32  is position between the lock arms  6 , due to the oblique angle of the lock arms  68  relative to the cylinder  32 . The oblique orientation of the end faces  76  also defines a trailing edge  78  on the lock arms  68 , the purpose of which is further discussed below. 
         [0055]    After activation of the pretensioner  10 , if the combustion head  30  and combustion cylinder  32  are urged in the playback direction, the length of the lock arms  68  cause the lock arms  68  to be compressively loaded and drives the trailing edges  78  into the outer surface of the combustion cylinder  32 . This engagement of the trailing edges  78  with the exterior surface of the combustion cylinder  32  locks the lock piece  62  with the combustion cylinder  32  and prevents the combustion head  30  from further moving in the playback direction. 
         [0056]    A second embodiment for locking the reaction housing  16  to the combustion cylinder  32 , upon the occurrence of movement in the playback direction, is illustrated in  FIGS. 6 and 7 . In this embodiment, the lock piece  62  is replaced with a one-way clutch assembly  80  that includes a series of roller balls or BBs  82  provided about the annular surface of the combustion cylinder  32 . Located outwardly of the BBs  82  is a conical surface  84  that is defined by inner surfaces of a lock collar  86 . The conical surface  84  is provided such that the narrower end of the surface  84  is disposed towards the reaction housing  16 . The wide end of the conical surface  84  is therefore disposed away from the reaction housing  16  and toward the combustion head  30 . 
         [0057]    The BBs  82  are dimensioned so that as the combustion cylinder  32  and combustion head  30  are moved in the activation direction A, the BBs  82  freely roll along the outer surface of the combustion cylinder  32 . Upon urging of the combustion head  30 , and the combustion cylinder  32 , in the playback direction, the BBs  82  are caused to roll along the conical surface  84  toward the narrower side thereof, in the direction of the reaction housing  16 . As a result, the BBs  82  eventually become wedged between the conical surface  84  and the annular outer surface of the combustion cylinder  32 . This wedging action of the BBs  82  prevents any further movement of the combustion cylinder  32  and combustion head  30  in the playback direction, thereby locking the pretensioner  10 . 
         [0058]    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.