Abstract:
There is provided in accordance with the present invention a seat belt retractor comprising a spool for carrying seat belt webbing rotatably mounted about a longitudinal axle and biased in a seat belt webbing rewinding direction, a toothed ratchet wheel mounted to rotate with the spool, a sensor for detecting an emergency condition, a vehicle acceleration sensor lever responsive to the sensor to engage the ratchet wheel in the event of an emergency condition, means for locking the spool against pay-out of seat belt webbing in response to the vehicle acceleration sensor lever engaging the ratchet wheel, the retractor being adapted to operate in a first, emergency locking mode in which the spool is not locked and can rotate to pay-out and to rewind seat belt webbing. In a second, automatic locking mode in which the spool is locked against pay-out of the seat belt webbing and means for switching between the first mode and the second mode, wherein, the switching means comprises a subassembly attached to a first end of said seat belt retractor, the subassembly having a housing, a plurality of annular axially adjacent disks mounted on a rotatable eccentric cam connected to said housing characterized by an axially directed spring biasing member to reduce axial spacing between said housing, eccentric cam and said plurality of annularly adjacent disks.

Description:
FIELD OF THE INVENTION  
       [0001]     The current invention relates to seat belt retractors.  
       BACKGROUND OF THE INVENTION  
       [0002]     A conventional seat belt retractor allows a vehicle occupant some freedom of movement, but has a sensor to detect acceleration above a predetermined magnitude indicative of an emergency situation. The seat belt retractor then locks, arresting the vehicle occupant&#39;s movement. This can also occur when the vehicle occupant leans forward too quickly to reach a control on the instrument panel. Seat belts which allow movement are desirable for adult vehicle occupants as they restrain passengers in emergency situations but are comfortable because they allow a reasonable degree of freedom for movement during normal driving conditions. When transporting a young child with a child seat the child seat must be fixed in place, but it is desirable for the same seat belt retractor to also operate as a normal inertial retractor to provide the expected comfort for an adult.  
         [0003]     This problem is a well known and several solutions have been proposed. U.S. Pat. No. 6,109,556 teaches a seat belt arrangement for motor vehicles, specially adapted for use with a child seat to switch between a fixed mode for the child seat and an automatic mode for adults. Such a seat belt retractor is known as a Child Hold Out Mechanism, sometimes referred to as a “CHOM”.  
         [0004]     U.S. Pat. No. 6,109,556 teaches a retractor switching means comprising a cam connected to a spool via a step down gearing arrangement and a cam follower. The step down gearing arrangement comprises an inner gear ring and a gear arrangement with a drive peg located at a predetermined radius. The drive peg is arranged to move cycloidally and rotate the cam when the gear rotates. This cycloidal motion often results in the gear arrangement being known as a “wobble” gear. The cam follower is pivotally mounted and arranged to be in continuous contact with the cam surface. At a predetermined rotational orientation of the cam, the cam follower urges the sensor lever into engagement with a toothed ratchet wheel fixed to the spool to lock the spool and seat belt webbing protraction.  
         [0005]     A particular problem with Child Hold Out Mechanism retractors is that a large number of components are needed and this increases the size of the retractor as well as introducing numerous components that generate noise commonly referred to as “rattle noise”.  
         [0006]     It is therefore an object of the present invention to provide a noise reducing feature to such seat belt retractors.  
       SUMMARY OF THE INVENTION  
       [0007]     There is provided in accordance with the present invention a seat belt retractor comprising a spool for carrying seat belt webbing rotatably mounted about a longitudinal axle and biased in a seat belt webbing rewinding direction, a toothed ratchet wheel mounted to rotate with the spool, a sensor for detecting an emergency condition, a vehicle acceleration sensor lever responsive to the sensor to engage the ratchet wheel in the event of an emergency condition, means for locking the spool against pay-out of seat belt webbing in response to the vehicle acceleration sensor lever engaging the ratchet wheel, the retractor being adapted to operate in a first, emergency locking mode in which the spool is not locked and can rotate to pay-out and to rewind seat belt webbing. In a second, automatic locking mode in which the spool is locked against pay-out of the seat belt webbing and means for switching between the first mode and the second mode, wherein, the switching means comprises a subassembly attached to a first end of said seat belt retractor, the subassembly having a housing, a plurality of annular axially adjacent disks mounted on a rotatable eccentric cam connected to said housing characterized by an axially directed spring biasing member to reduce axial spacing between said housing, eccentric cam and said plurality of annularly adjacent disks.  
         [0008]     The subassembly may further include a drive pin mounted at a first end of said axle of said seat belt retractor and fixedly attached to said eccentric cam to provide rotational movement of said cam as said seat belt webbing is protracted.  
         [0009]     The plurality of axially adjacent disks include a gear having an axially projecting pin; a child hold out mechanism disk having a slot for accepting said projecting pin; and a blockout disk having an opening for accepting said pin.  
         [0010]     In a preferred embodiment the axially directed spring biasing member is an integral portion of one of said disk, more preferably in the child holdout mechanism disk includes the integral axially directed spring biasing member formed as an inner ring or projecting appendage portion mounted on said eccentric cam as a split ring. The split ring forms a spiraled ring having an axially projecting end when formed as a ring the ring is cut having a projecting end which provides a spring biasing force. The axially directed spring biasing member extends axially from the disk generally planar surface a distance (y) and wherein a gap (g) between a flange on said eccentric cam and the plurality of disks and as measured as the distance X between an inside surface of the housing and an inside surface of the cam flange minus the combined axial thickness of the disks is (g), wherein (g) is less than (y). Similarly when formed as a projecting appendage that portion acts as a leaf spring also projecting a distance (y) greater than the gap (g) The spring biasing member applies a force to insure at least partial contact between each axially adjacent component sufficing to reduce rattle noise. The spring biasing member can be radially adjacent the eccentric cam. When the axially directed spring biasing member is interposed between two adjacent disks the disks are held apart by a distance approximating or substantially equal to said gap (g). This insures the opposing surfaces of said disks are spaced and to contact the disks must overcome the spring force. This provides an overall noise reduction of the seat belt retractor subassembly.  
         [0000]     Definitions  
         [0011]     “Axial” means in a direction parallel to an axle of the seat belt retractor.  
         [0012]     “ALR” means Automatic Locking Retractor.  
         [0013]     “CHOM” means Child Holdout Mechanism.  
         [0014]     “ELR” means Emergency Locking Retractor.  
         [0015]     “Radial” means in a direction extending from the axis of rotation of the axle of the seat belt retractor.  
         [0016]     “Wobble Gear” means a cycloidal gear. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a partially exploded perspective view of an exemplary seat belt retractor according to the present invention.  
         [0018]      FIG. 2  is a perspective view of a CHOM disk according to the prior art.  
         [0019]      FIG. 3  is a plan view of the prior art CHOM disk of  FIG. 2 .  
         [0020]      FIG. 4  is a cross sectional view of the prior art CHOM disk.  
         [0021]      FIG. 5  is a perspective view of a CHOM disk according to a first embodiment of the invention.  
         [0022]      FIG. 6  is a plan view of the CHOM disk of  FIG. 5 .  
         [0023]      FIG. 7  is a cross sectional view taken along lines  7 - 7  of the CHOM disk of  FIG. 6 .  
         [0024]      FIG. 8  is a perspective view of a second and preferred embodiment CHOM disk according to the present invention.  
         [0025]      FIG. 9  is a plan view of the CHOM disk of  FIG. 8 .  
         [0026]      FIG. 10  is a side view of the CHOM disk of  FIG. 8 .  
         [0027]      FIG. 11  is a cross sectional view of the CHOM disk of  FIG. 9  taken along lines  11 - 11 .  
         [0028]      FIG. 12  is an exploded perspective view of a subassembly according to the present invention.  
         [0029]      FIG. 13  is an assembled side view of the subassembly of  FIG. 12 .  
         [0030]      FIG. 14  is an assembled cross sectional view of  FIG. 13  taken along lines  14 - 14 .  
         [0031]      FIG. 14A  is an enlarged portion of the cross section of  FIG. 14  taken within the dashed lines marked  14 A.  
         [0032]      FIG. 15  is an end view of the seat belt retractor with the subassembly shown mounted to the retractor according to the present invention.  
         [0033]      FIG. 16  is a cross sectional view of the seat belt retractor of  FIG. 15  taken along lines  16 - 6 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     In  FIG. 1 , an exemplary vehicle seat belt retractor  100  is shown with the seat belt webbing  21  substantially fully protracted from a spool  1  mounted in a frame  2  with a subassembly shown in an exploded view detached from the end of the retractor. Thus the individual parts of the mechanism can be more clearly seen. Like reference signs are used throughout the figures. The seat belt retractor  100  comprises a lock bar  3 , a pivotable mounting member  4 , drive pin  5 , a drive axle  50 , a vehicle acceleration sensor  6 , a vehicle acceleration sensor lever  7  pivotable about a pivot point  7   b , an inner gear ring  8 , a wobble gear arrangement  9 , a pin  10 , an eccentric cam  11 , a CHOM disk  12  with a cam surface having an indentation  13  therein comprising a ramp  13   a  and a step  13   b  that is substantially radial to the cam surface for engaging an actuation lever  15 , a window or slot  14 , an actuation lever pivot fastener  16 , an actuation lever spring  17 , a mounting member spring  18 , a ratchet wheel  19 , a lock gear  20 , a fixed mounting member  22  and mounting lugs  23 . The actuation lever  15  has a relatively smaller contact area with the cam surface of the CHOM disk  12  when not in engagement with the indentation  13  in the cam surface than when in engagement with the indentation in the cam surface.  
         [0035]     The exemplary seat belt retractor  100  of the figures operates in two distinct modes: a first, Emergency Locking Retractor (ELR), mode; and a second, Automatic Locking Retractor (ALR), mode. In ELR mode, seat belt webbing  21  can be wound onto the spool  1  and pulled from the spool  1 . This allows the vehicle occupant to move freely to, for example, adjust a radio or a control on a vehicle instrument panel. Sudden movements however, which have an acceleration greater than a predetermined magnitude, for example caused by a sharp vehicle deceleration, cause the seat belt retractor to lock. This prevents further payout of the seat belt webbing  21  and restrains the vehicle occupant. Most vehicle occupants use the seat belt retractor in ELR mode.  
         [0036]     In ALR mode, seat belt webbing  21  can be retracted on to the spool  1  but not pulled from the spool  1 . This mode is used when restraining a child seat in a vehicle.  
         [0037]     To switch to ALR mode, a predetermined amount of seat belt webbing  21  is pulled from the spool  1 . This activates a mechanism that locks the spool  1  against further payout of seat belt webbing  21 .  
         [0038]     Usually this switching occurs when substantially the whole of the seat belt webbing  21  is retracted, for example, is wound on the spool  1 . The spool  1  is biased in the retraction direction of the seat belt webbing  21 .  
         [0039]      FIG. 1  is a partially exploded view of the subassembly of the seat belt retractor  100  shown. This clearly shows the housing  31 , the drive pin  5 , the wobble gear  9 , the pin  10 , located on the wobble gear  9 , the eccentric cam  11 , the CHOM disk  12  with the window  14  cut through the CHOM disk  12 , the blockout disk  40  and the actuation lever  15 .  
         [0040]     The window or slot  14  comprises a concentric arcuate slot cut through the face of the CHOM disk  12  and having an inner wall and an outer wall at respective predetermined radii from the center of the cam and each having a predetermined arcuate length. In the particular embodiment shown, the arcuate slot  14  extends through an angle of just less than 180 degrees.  
         [0041]     The pin  10  is located at a predetermined radius on the wobble gear  9 . The position of the pin  10  within the slot  14  is determined by the amount of seat belt webbing  21  that has been pulled from the spool  1 .  
         [0042]     The actuation lever  15  is pivotally attached to the pivotable mounting member  4  at the pivot point fastener  16 . One portion of the actuation lever  15  is biased towards the cam surface of CHOM disk  12  by the actuation lever spring  17 . In the embodiment shown, in the actuation lever spring  17  is a helical spring in compression and causes the actuation lever  15  to remain in contact with the cam surface of the CHOM disk  12  irrespective of the rotational orientation of the CHOM disk  12 .  
         [0043]     A mounting member  22  is fixedly attached to a frame  2 . The fixed mounting member  22  can be made of a plastic material and the frame  2  can be made of metal.  
         [0044]     The vehicle acceleration sensor lever  7  is pivotally mounted to the pivotable mounting member  4  at a pivot point  7   b . The vehicle acceleration sensor  6  is a standing man sensor, well known in the art, that is mounted on the pivotable mounting member  4  to detect vehicle accelerations and decelerations above a predetermined magnitude and upon detection of said accelerations/decelerations to bias the vehicle acceleration sensor lever against at least one tooth on the ratchet wheel. The vehicle acceleration sensor  6  may take other forms. The internal gear ring  8  is fixed to the housing  31  as best seen in  FIG. 15 . In one embodiment, the step-down gearing is a cycloidal gear system commonly known as a wobble gear  9 . However, other step-down gearing can be used. Preferably, the step-down gearing is a cycloidal system comprising an eccentric cam. The drive pin  5 , the eccentric cam  11 , the wobble gear  9  and the CHOM disk  12  can all move relative to the pivotable mounting member  4 .  
         [0045]     Fixedly mounted to the drive axle  50  are a ratchet wheel  19  and a lock gear  20 , as shown in  FIG. 1 . The vehicle acceleration sensor  6  detects accelerations/decelerations above a predetermined magnitude. When accelerations/decelerations are below the predetermined magnitude, the vehicle acceleration sensor lever  7 , pivotable about a pivot point  7   b  is not engaged with the ratchet wheel  19 . This allows rotation of the spool  1  and hence the eccentric cam  5 , ratchet wheel  19  and lock gear  20 , in both seat belt webbing  21  extraction and retraction directions. When the vehicle acceleration sensor  6  detects accelerations/decelerations above a predetermined magnitude, the vehicle acceleration sensor lever  7  pivots about the pivot point  7   b  and engages with at least one tooth on the ratchet wheel  19 . Preferably, the vehicle acceleration sensor lever  7  is the only lever arranged to engage the ratchet wheel  19 . This allows a relatively substantial reduction in size over known seat belt retractors of this type that use additional levers to engage the ratchet. One portion of the vehicle acceleration sensor lever  7  is arranged to co-operate with the sensor  6  and another portion is arranged for engagement with the ratchet wheel  19  and wherein the pivot point  7   b  of the vehicle acceleration sensor lever  7  is located between each of said portions. Any further rotation of the spool  1 , and hence the drive axle  50 , the ratchet wheel  19  and the lock gear  20 , in the direction of seat belt webbing  21  pay-out, is communicated by the vehicle acceleration sensor lever  7  to the pivotable mounting member  4  causing it to rotate in the same direction as the spool  1 , compressing the mounting member spring  18  and causing the lock bar  3 , which is pivotally mounted on the frame  2  to engage with the lock gear  20  fully arresting the rotation of the spool  1 . This happens during vehicle crashes and when a vehicle occupant pulls too sharply on the seat belt webbing  21 .  
         [0046]     The operation of the seat belt retractor as it switches from ELR mode, as shown, into ALR mode, is more fully described in U.S. Pat. No. 6,631,865 which is incorporated herein by reference in its entirety. For purposes of this invention the actual performance of the mechanism is somewhat irrelevant except for the fact that the functioning of the seat belt retractor and more specifically the child holdout mechanism subassembly must not be impeded by the addition of the noise dampening features described below.  
         [0047]     With reference to  FIGS. 2-4  a prior art CHOM disk  12  is shown the CHOM disk  12  has the window or arcuate slot  14  and cam surface  13  as illustrated. At the inner diameter of the CHOM disk  12  is shown an annular ring  12   a , this annular ring  12   a  is adapted to be mounted on the eccentric cam  11 . As shown in the cross sectional view the CHOM disk  12  has a substantially parallel and planar surface having a thickness (t).  
         [0048]     With reference to  FIGS. 5, 6  and  7  a CHOM disk  12  according to a first embodiment of the present invention is shown. The CHOM disk  12  is modified such that an appendage  12   c  is illustrated wherein the appendage  12   c  acts as a leaf spring or axially directed spring biasing member projecting outward from the surface as shown in  FIG. 7 . This slight projection outward from the surface creates an axially directed spring force to be generated when the assembly is made such that the CHOM disk  12  exerts an axial force against the other components thereby taking the slack out and any gap (g) that might be created during the assembly. This is particularly important in mass production wherein tolerance stack ups are such that one must provide a sufficient amount of gap (g) so that all the components can be adequately assembled otherwise the components will simply not fit when assembled.  
         [0049]     With reference to  FIGS. 8, 9 ,  10  and  11  a preferred and second embodiment of the present invention is shown wherein the CHOM disk  12  has the inner ring portion  12   a  split in such a fashion that an end  12   b  is projecting outward from the surface, this end  12   b  projects out a distance (y) from the planar surface, this distance (y) is sufficiently wider than any tolerance gap (g) created by the assembly of components as the components are mounted the end  12   b  deflects by an amount of (g) such that the gap (g) is eliminated completely this insures that all the components are assembled and in contact such that no rattle or vibration noises can be heard during normal operation of the vehicle. This split ring  12   b  acts as the axially directed spring biasing member.  
         [0050]     With reference to  FIGS. 12, 13 ,  14  and  15  the CHOM subassembly  30  is shown in exploded view in  FIG. 12  on the far left is the drive pin  5 , the eccentric cam  11 , the blockout disk  40 , the CHOM disk  12 , and the wobble gear  9  as can be seen the eccentric cam  11  has a protruding flange  11   c  that retains the disk components and gears such that they are positioned between the flange  11   c  and the housing  31 . With reference to  FIG. 15  the end of the housing  31  on the inner surface includes the inner ring gear  8  which is complimentary to the wobble gear  9 . With further reference to  FIG. 14  as shown when the components are assembled the eccentric cam  11  has a projecting portion  11   a  that matingly engages with an opening  30   a  on the housing  31  such that they are captively retained holding all of the working mechanisms such as the disk  12 ,  40  and gear  9  and cam  11 . At the opposite end, the drive pin  5  has an end portion  5   b  that is inserted into the eccentric cam opening  11   b  such that the drive pin  5  and eccentric cam  11  are adapted to rotate together when being driven by the drive axle  50 . As further illustrated in  FIG. 13  mounting projections  32  are provided on the exterior of the housing  31  in three locations. These mounting projections  32  are spring loaded such that it can be snapped into the retractor frame  2  at the hole locations  27 . This is shown more clearly in  FIG. 16  wherein the housing  31  is shown physically mounted to the frame  2 . The drive pin  5  has an end  5   b  adapted to engage the axle opening  50   a  within the axle  50 . With reference to  FIG. 14  and  FIG. 14A  as can be seen each of the components, the wobble gear  9 , the CHOM disk  12  and the blockout disk  40 , each have a thickness (t) when mounted to the eccentric cam  11  the distance between the flange  11   c  and the inside wall of the housing  31  is represented as a distance X. Absent the present invention&#39;s axially directed spring member  12   c , the disks and gear components would have a gap (g), g being the distance between the distance X and each of the components cumulative thickness (t). By providing this axially directed spring member  12   c  a deflection occurs such that the spring member  12   c  is pushed back taking up all the slack between the members such that they are all in contact and slightly pre loaded in the axial direction such that any noise or rattle due to the parts vibrating during normal use is eliminated and virtually reduced to zero. In order for the parts to rattle the spring force must be overcome by an acceleration of the various components. Since each of the components is made of plastic and relatively lightweight a significant amount of acceleration or vibration is required in order to stimulate a sufficient reaction to overcome the biasing spring force.  
         [0051]     While it is the intention of the present invention to provide an efficient child holdout mechanism subassembly  30  that is both reliable and quiet it is also understood that this child holdout mechanism subassembly  30  is clearly adaptable to any number of seat belt retractors. These seat belt retractors can take a variety of shapes and sizes and accordingly the use of the noise reducing features may be modified as required, however, it is sufficient to indicate that the exemplary seat belt retractor  100  is provided only for purpose of illustration in explaining the design concept and how the noise reduction is achieved in the subassembly of components. Accordingly, it is understood that variations in the subassembly  30  can occur and that the axially directed spring biasing member can be provided on any of the rotating disk members including the wobble gear itself should that be desired. Alternatively, the spring biasing member could be provided as a separate component that provides sufficient absorption of the gap upon assembly such that the noise rattling feature can be achieved whether the component is integral to the disk which is the preferred method because it requires no additional components or whether it is provided as a separate component. In either case the beneficial attributes of reducing rattle within the assembly is achieved.  
         [0052]     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.