Patent Document

FIELD 
     The present disclosure relates generally to hydraulic dampers or shock absorbers for use in a suspension system such as a suspension system used for automotive vehicles. More particularly, the present disclosure relates to a hydraulic damper or shock absorber which includes a jounce bumper nose retaining feature which interacts with the jounce bumper to eliminate sliding and noise. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Shock absorbers are used in conjunction with automotive suspension systems to absorb unwanted vibrations which occur during driving. To absorb the unwanted vibrations, shock absorbers are generally connected between the sprung portion (body) and the unsprung portion (suspension) of the automobile. A piston is located within a pressure tube of the shock absorber and the pressure tube is connected to one of the sprung portion and the unsprung portion of the vehicle. The piston is connected to the other of the sprung portion and unsprung portion of the automobile through a piston rod which extends through the pressure tube. The piston divides the pressure tube into an upper working chamber and a lower working chamber both of which are filled with hydraulic fluid. Because the piston is able, through valving, to limit the flow of the hydraulic fluid between the upper and the lower working chambers when the shock absorber is compressed or extended, the shock absorber is able to produce a damping force which counteracts the vibration which would otherwise be transmitted from the unsprung portion to the sprung portion of the vehicle. In a dual-tube shock absorber, a fluid reservoir or reserve chamber is defined between the pressure tube and a reserve tube. A base valve is located between the lower working chamber and the reserve chamber to also produce a damping force which counteracts the vibrations which would otherwise be transmitted from the unsprung portion of the vehicle to the sprung portion of the automobile. 
     As described above, for a dual-tube shock absorber, the valving on the piston limits the flow of damping fluid between the upper and lower working chambers when the shock absorber is extended to produce a damping load. The valving on the base valve limits the flow of damping fluid between the lower working chamber and the reserve chamber when the shock absorber is compressed to produce a damping load. For a mono-tube shock absorber, the valving on the piston limits the flow of damping fluid between the upper and lower working chambers when the shock absorber is extended or compressed to produce a damping load. During driving, the suspension system moves in jounce (compression) and rebound (extension). During jounce movements, the shock absorber is compressed causing damping fluid to move through the base valve in a dual-tube shock absorber or through the piston valve in a mono-tube shock absorber. A damping valve located on the base valve or the piston controls the flow of damping fluid and thus the damping force created. During rebound movements, the shock absorber is extended causing damping fluid to move through the piston in both the dual-tube shock absorber and the mono-tube shock absorber. A damping valve located on the piston controls the flow of damping fluid and thus the damping force created. 
     In a dual-tube shock absorber, the piston and the base valve normally include a plurality of compression passages and a plurality of extension passages. During jounce movements in a dual-tube shock absorber, the damping valve or the base valve opens the compression passages in the base valve to control fluid flow and produce a damping load. A check valve on the piston opens the compression passages in the piston to replace damping fluid in the upper working chamber but this check valve may or may not contribute to the damping load. The damping valve on the piston closes the extension passages of the piston and a check valve on the base valve closes the extension passages of the base valve during a compression movement. During rebound movements in a dual-tube shock absorber, the damping valve on the piston opens the extension passages in the piston to control fluid flow and produce a damping load. A check valve on the base valve opens the extension passages in the base valve to replace damping fluid in the lower working chamber but this check valve may or may not contribute to the damping load. 
     In a mono-tube shock absorber, the piston normally includes a plurality of compression passages and a plurality of extension passages. The shock absorber will also include means for compensating for the rod volume flow of fluid as is well known in the art. During jounce movements in a mono-tube shock absorber, the compression damping valve on the piston opens the compression passages in the piston to control fluid flow and produce a damping load. The extension damping valve on the piston closes the extension passages of the piston during a jounce movement. During rebound movements in a mono-tube shock absorber, the extension damping valve on the piston opens the extension passages in the piston to control fluid flow and produce a damping load. The compression damping valve on the piston closes the compression passages of the piston during a rebound movement. 
     Shock absorbers typically include an elastomeric jounce bumper which is disposed around the piston rod. During maximum compression of the shock absorber, the elastomeric jounce bumper contacts a jounce bumper cap which is attached to the shock absorber. Continued compression of the shock absorber compresses the elastomeric jounce bumper to dissipate energy. The jounce bumper cap is configured to protect the upper end of the shock absorber tubes and the seal assembly for the piston rod. During compression of the elastomeric jounce bumper, the elastomeric jounce bumper will typically slide relative to the jounce bumper cap causing unwanted noise. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     The present disclosure relates to a hydraulic damper or shock absorber which includes a jounce bumper cap nose retaining feature which interacts with the elastomeric jounce bumper to eliminate sliding of the elastomeric jounce bumper relative to the jounce bumper cap to eliminate the noise associated with this sliding movement. The feature incorporated into the jounce bumper cap in one embodiment is an annular protrusion which extends towards the elastomeric jounce bumper. In a second embodiment, the feature incorporated into the jounce bumper cap is a plurality of annular grooves which form a plurality of annular ridges or teeth. The feature incorporated into the jounce bumper cap changes the jounce bumper cap geometry so that the jounce bumper cap captures the nose of the elastomeric jounce bumper and thus the elastomeric jounce bumper compresses and does not slide relative to the jounce bumper cap. The profile of the annular protrusion is tunable based on the interaction of the elastomeric jounce bumper to prevent noise. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is an illustration of an automobile using the shock absorber in accordance with the present disclosure; 
         FIG. 2  is a side view of a corner assembly that incorporates the shock absorbers in accordance with the present disclosure; 
         FIG. 3  is a side sectional view of a shock absorber which incorporates the nose cap retaining feature on the jounce bumper cap; 
         FIG. 4  is an enlarged side view, partially in cross-section, of the piston assembly from the shock absorber illustrated in  FIG. 3 ; 
         FIG. 5  is an enlarged side view, partially in cross-section of the base valve assembly from the shock absorber illustrated in  FIG. 3 ; 
         FIG. 6  is an enlarged cross-section of the elastomeric jounce bumper and the jounce bumper cap for the shock absorber in  FIG. 3 ; 
         FIG. 7  is a perspective view of the jounce bumper cap illustrated in  FIG. 6 ; 
         FIG. 8  is a side view in cross-section of the jounce bumper cap illustrated in  FIG. 7 ; 
         FIG. 9  is a perspective view of a jounce bumper cap in accordance with another embodiment of the present disclosure; and 
         FIG. 10  is a side view in cross-section of the jounce bumper cap illustrated in  FIG. 9 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     There is shown in  FIG. 1  a vehicle incorporating a suspension system having a shock absorber in accordance with the present disclosure and which is designated generally by the reference numeral  10 . Vehicle  10  comprises a rear suspension  12 , a front suspension  14  and a body  16 . Rear suspension  12  has a transversely extending rear axle assembly (not shown) adapted to operatively support the vehicle&#39;s rear wheels  18 . The rear axle assembly is operatively connected to body  16  by means of a pair of corner assemblies  20  which include a pair of shock absorbers  22  and a pair of helical coil springs  24 . Similarly front suspension  14  includes a transversely extending front axle assembly (not shown) to operatively support the vehicle&#39;s front wheels  26 . The front axle assembly is operatively connected to body  16  by means of a second pair of corner assemblies  28  which include a pair of shock absorbers  30  and by a pair of shaped helical coil springs  32 . Shock absorbers  22  and  30  serve to dampen the relative motion of the unsprung portion (i.e. front and rear suspensions  12  and  14 , respectively) and the sprung portion (i.e. body  16 ) of vehicle  10 . While vehicle  10  has been depicted as a passenger car having front and rear axle assemblies, shock absorbers  22  and  30  may be used with other types of vehicles and/or in other types of applications such as vehicles incorporating independent front and/or independent rear suspension systems. Further, the term “shock absorber” as used herein is meant to be dampers in general and thus will include struts. Also, while front suspension  14  is illustrated having a pair of struts or shock absorbers  30 , it is within the scope of the present invention to have rear suspension  12  incorporate a pair of struts or shock absorbers  30  if desired. 
     Referring now to  FIG. 2 , the front corner assembly  28  for vehicle  10  is illustrated in greater detail. Body  16  defines a shock tower  34  comprising sheet metal of vehicle  10  within which is mounted a strut assembly  36  which comprises a telescoping device in the form of shock absorber  30 , coil spring  32 , a top mount assembly  38  and a knuckle  40 . Strut assembly  36  including shock absorber  30 , coil spring  32  and top mount assembly  38  are attached to vehicle  10  using shock tower  34 . Top mount assembly  38  comprises a top mount  42 , a bearing assembly  44  and an upper spring seat  46 . Top mount  42  comprises an integral molded body and a rigid body member, typically made of stamped steel. Top mount assembly  38  is mounted to shock tower  34  by bolts  48 . Bearing assembly  44  is friction fit within the molded body of top mount  42  to be seated in top mount  42  so that one side of bearing assembly  44  is fixed relative to top mount  42  and shock tower  34 . The second side of bearing assembly  44  freely rotates with respect to the first side of bearing assembly  44 , top mount  42  and shock tower  34 . 
     The free rotating side of bearing assembly  44  carries upper spring seat  46  that is clearance fit to the outer diameter of bearing assembly  44 . An elastomeric jounce bumper  50  is disposed between upper spring seat  46  and shock absorber  30 . Elastomeric jounce bumper  50  comprises an elastomeric material which is protected by a plastic dirt shield  52 . A jounce bumper cap  54  is located on shock absorber  30  to interface with elastomeric jounce bumper  50  and plastic dirt shield  52 . 
     A lower spring seat  56  is attached to shock absorber  30  and coil spring  32  is disposed between upper spring seat  46  and lower spring seat  56  to isolate body  16  from front suspension  14 . While shock absorber  30  is illustrated in  FIG. 2 , it is to be understood that shock absorber  22  may also include the features described herein for shock absorber  30 . 
     Prior to the assembly of strut assembly  36  into vehicle  10 , the pre-assembly of strut assembly  36  is performed. Jounce bumper cap  54 , elastomeric jounce bumper  50  and plastic dirt shield  52  are assembled to shock absorber  30 . Coil spring  32  is assembled over shock absorber  30  and positioned within lower spring seat  56 . Upper spring seat  46  is assembled onto shock absorber  30  and correctly positioned with respect to coil spring  32 . Bearing assembly  44  is positioned on top of upper spring seat  46  and top mount  42  is positioned on top of bearing assembly  44 . This entire assembly is positioned within an assembly machine which compresses coil spring  32  such that the end of shock absorber  30  extends through a bore located within top mount assembly  38 . A retaining nut  58  is threadingly received on the end of shock absorber  30  to secure the assembly of strut assembly  36 . 
     Top mount  42  is designed as an identical component for the right and left hand sides of the vehicle but it has a different orientation with respect to shock absorber  30  and its associated bracketry when it is placed on the right or left side of the vehicle. 
     Referring now to  FIG. 3 , shock absorber  30  is shown in greater detail. While  FIG. 3  illustrates only shock absorber  30 , it is to be understood that shock absorber  22  could also be a part of a strut assembly and include the reinforcement described below for shock absorber  30 . Shock absorber  30  comprises a pressure tube  60 , a piston assembly  62 , a piston rod  64 , a reserve tube assembly  66  and a base valve assembly  68 . 
     Pressure tube  60  defines a fluid chamber  72 . Piston assembly  62  is slideably disposed within pressure tube  60  and divides fluid chamber  72  into an upper working chamber  74  and a lower working chamber  76 . A seal  78  is disposed between piston assembly  62  and pressure tube  60  to permit sliding movement of piston assembly  62  with respect to pressure tube  60  without generating undue frictional forces as well as sealing upper working chamber  74  from lower working chamber  76 . Piston rod  64  is attached to piston assembly  62  and extends through upper working chamber  74  and through an upper end cap  80  which closes the upper end of pressure tube  60 . A sealing system seals the interface between upper end cap  80 , reserve tube assembly  66  and piston rod  64 . The end of piston rod  64  opposite to piston assembly  62  is adapted to be secured to top mount assembly  38  and to the sprung portion of vehicle  10  as discussed above. Valving within piston assembly  62  controls the movement of fluid between upper working chamber  74  and lower working chamber  76  during movement of piston assembly  62  within pressure tube  60 . Because piston rod  64  extends only through upper working chamber  74  and not lower working chamber  76 , movement of piston assembly  62  with respect to pressure tube  60  causes a difference in the amount of fluid displaced in upper working chamber  74  and the amount of fluid displaced in lower working chamber  76 . The difference in the amount of fluid displaced is known as the “rod volume” and it flows through base valve assembly  68 . 
     Reserve tube assembly  66  surrounds pressure tube  60  to define a fluid reservoir chamber  82  located between pressure tube  60  and reserve tube assembly  66 . The bottom end of reserve tube assembly  66  is closed by an end cap  84 . While end cap  84  is illustrated as a separate component, it is within the scope of the present disclosure to have end cap  84  integral with reserve tube assembly  66 . The upper end of reserve tube assembly  66  is attached to upper end cap  80 . The lower end of reserve tube assembly  66  defines a reinforced portion  86  which interfaces with knuckle  40 . The remaining length of reserve tube assembly  66  defines a non-reinforced portion  88 . Base valve assembly  68  is disposed between lower working chamber  76  and reservoir chamber  82  to control the flow of fluid between chambers  76  and  82 . When shock absorber  30  extends in length, an additional volume of fluid is needed in lower working chamber  76  due to the “rod volume” concept. Thus, fluid will flow from reservoir chamber  82  to lower working chamber  76  through base valve assembly  68  as detailed below. When shock absorber  30  compresses in length, an excess of fluid must be removed from lower working chamber  76  due to the “rod volume” concept. Thus, fluid will flow from lower working chamber  76  to reservoir chamber  82  through base valve assembly  68  as detailed below. 
     Referring now to  FIG. 4 , piston assembly  62  comprises a piston body  90 , a compression valve assembly  92  and a rebound valve assembly  94 . Compression valve assembly  92  is assembled against a shoulder  96  on piston rod  64 . Piston body  90  is assembled against compression valve assembly  92  and rebound valve assembly  94  is assembled against piston body  90 . A nut  98  secures these components to piston rod  64 . 
     Piston body  90  defines a plurality of compression passages  100  and a plurality of rebound passages  102 . Seal  78  includes a plurality of ribs  104  which mate with a plurality of annular grooves  106  to restrict sliding movement of seal  78  relative to piston body  90  as piston assembly  62  slides in pressure tube  60 . 
     Compression valve assembly  92  comprises a retainer  108 , a valve disc  110  and a spring  112 . Retainer  108  abuts shoulder  96  on one end and piston body  90  on the other end. Valve disc  110  abuts piston body  90  and closes compression passages  100  while leaving rebound passages  102  open. Spring  112  is disposed between retainer  108  and valve disc  110  to bias valve disc  110  against piston body  90 . During a compression stroke, fluid in lower working chamber  76  is pressurized causing fluid pressure to react against valve disc  110 . When the fluid pressure against valve disc  110  overcomes the biasing load of spring  112 , valve disc  110  separates from piston body  90  to open compression passages  100  and allow fluid flow from lower working chamber  76  to upper working chamber  74 . The damping characteristics for shock absorber  30  during a compression stroke of shock absorber  30  can be controlled by compression valve assembly  92  and/or base valve assembly  68  which accommodates the flow of fluid from lower working chamber  76  to reservoir chamber  82  due to the “rod volume” concept as detailed below. During a rebound stroke, compression passages  100  are closed by valve disc  110 . 
     Rebound valve assembly  94  comprises a spacer  114 , a plurality of valve discs  116 , a retainer  118  and a spring  120 . Spacer  114  is threadingly received on piston rod  64  and is disposed between piston body  90  and nut  98 . Spacer  114  retains piston body  90  and compression valve assembly  92  while permitting the tightening of nut  98  without compressing either valve disc  110  or valve discs  116 . Retainer  108 , piston body  90  and spacer  114  provide a continuous solid connection between shoulder  96  and nut  98  to facilitate the tightening and securing of nut  98  to spacer  114  and thus to piston rod  64 . Valve discs  116  are slidingly received on spacer  114  and abut piston body  90  to close rebound passages  102  while leaving compression passages  100  open. Retainer  118  is also slidingly received on spacer  114  and it abuts valve discs  116 . Spring  120  is assembled over spacer  114  and is disposed between retainer  118  and nut  98  which is threadingly received on spacer  114 . Spring  120  biases retainer  118  against valve discs  116  and valve discs  116  against piston body  90 . Valve discs  116  includes at least one slot  122  which permits a limited amount of bleed flow bypassing rebound valve assembly  94 . When fluid pressure is applied to valve discs  116 , they will elastically deflect at the outer peripheral edge to open rebound valve assembly  94 . A shim  124  is located between nut  98  and spring  120  to control the preload for spring  120  and thus the blow off pressure as described below. Thus, the calibration for the blow off feature of rebound valve assembly  94  is separate from the calibration for compression valve assembly  92 . 
     During a rebound stroke, fluid in upper working chamber  74  is pressurized causing fluid pressure to react against valve discs  116 . When the fluid pressure reacting against valve discs  116  overcomes the bending load for valve discs  116 , valve discs  116  elastically deflect opening rebound passages  102  allowing fluid flow from upper working chamber  74  to lower working chamber  76 . The strength of valve discs  116  and the size of rebound passages  102  will determine the damping characteristics for shock absorber  30  in rebound. Prior to the deflection of valve discs  116 , a controlled amount of fluid flows from upper working chamber  74  to lower working chamber  76  through slot  122  to provide low speed tunability. When the fluid pressure within upper working chamber  74  reaches a predetermined level, the fluid pressure will overcome the biasing load of spring  120  causing axial movement of retainer  118  and the plurality of valve discs  116 . The axial movement of retainer  118  and valve discs  116  fully opens rebound passages  102  thus allowing the passage of a significant amount of damping fluid creating a blowing off of the fluid pressure which is required to prevent damage to shock absorber  30  and/or vehicle  10 . Additional fluid required to be added to lower working chamber  76  due to the “rod volume” concept will flow through base valve assembly  68 . 
     Referring to  FIG. 5 , base valve assembly  68  comprises a valve body  142 , a compression valve assembly  144  and a rebound valve assembly  146 . Compression valve assembly  144  and rebound valve assembly  146  are attached to valve body  142  using a bolt  148  and a nut  150 . The tightening of nut  150  biases compression valve assembly  144  towards valve body  142 . Valve body  142  defines a plurality of compression passages  152  and a plurality of rebound passages  154 . 
     Compression valve assembly  144  comprises a plurality of valve discs  156  that are biased against valve body  142  by bolt  148  and nut  150 . During a compression stroke, fluid in lower working chamber  76  is pressurized and the fluid pressure within compression passages  152  will eventually open compression valve assembly  144  by deflecting valve discs  156 . Compression valve assembly  92  of piston assembly  62  will allow fluid flow from lower working chamber  76  to upper working chamber  74  and only the “rod volume” will flow through compression valve assembly  144 . The damping characteristics for shock absorber  30  are determined by the design of compression valve assembly  144  of base valve assembly  68  and can also be determined by compression valve assembly  92 . 
     Rebound valve assembly  146  comprises a valve disc  158  and a valve spring  160 . Valve disc  158  abuts valve body  142  and closes rebound passages  154 . Valve spring  160  is disposed between nut  150  and valve disc  158  to bias valve disc  158  against valve body  142 . During a rebound stroke, fluid in lower working chamber  76  is reduced in pressure causing fluid pressure in reservoir chamber  82  to react against valve disc  158 . When the fluid pressure against valve disc  158  overcomes the biasing load of valve spring  160 , valve disc  158  separates from valve body  142  to open rebound passages  154  and allow fluid flow from reservoir chamber  82  to lower working chamber  76 . The damping characteristics for a rebound stroke can be controlled by rebound valve assembly  94  as detailed above and can also be controlled by rebound valve assembly  146 . 
     Referring now to  FIGS. 6-8 , elastomeric jounce bumper  50  and jounce bumper cap  54  are illustrated in greater detail. Elastomeric jounce bumper  50  is an elastomeric member which extends from upper spring seat  46  toward jounce bumper cap  54  and upper end cap  80  along piston rod  64 . Elastomeric jounce bumper  50  is an annular member which fully encircles piston rod  64 . 
     Jounce bumper cap  54  is an annular member made from plastic, a polymer or metal which defines a through bore  170  through which piston rod  64  extends. A jounce bumper nose retaining feature  172  in the form of an annular protrusion  174  extends around through bore  170  and extends axially in a direction facing or toward elastomeric jounce bumper  50 . Jounce bumper cap  54  defines an interface surface  176  which extends radially outward from jounce bumper nose retaining feature  172 . During compression of elastomeric jounce bumper  50 , interface surface  176  defines a stop for elastomeric jounce bumper  50  which causes the compression of elastomeric jounce bumper  50 . The end of jounce bumper cap  54  opposite to interface surface  176  defines an engagement surface which is configured to mate with the outer surface of upper end cap  80 . 
     During a compression stroke for shock absorber  30 , when shock absorber  30  nears its fully compressed condition, a nose  178  of elastomeric jounce bumper  50  will first contact jounce bumper retaining feature  172 . Further compression of shock absorber  30  will cause jounce bumper nose retaining feature  172  to locally compress nose  178  and nose  178  will eventually engage interface surface  176 . Further compression of shock absorber  30  will cause further compression of elastomeric jounce bumper  50  and further engagement with interface surface  176 . Jounce bumper nose retaining feature  172  provides a retaining function which reduces or eliminates any radial movement of elastomeric jounce bumper  50  with respect to interface surface  176  of jounce bumper cap  54  to eliminate any noise generation generated by the sliding motion of elastomeric jounce bumper  50  along interface surface  176 . 
     Referring now to  FIGS. 9 and 10 , a jounce bumper cap  254  in accordance with another embodiment of the present disclosure is illustrated. Jounce bumper cap  254  is the same as jounce bumper cap  54  except for the jounce bumper retaining feature. 
     Jounce bumper cap  254  is an annular member made from plastic, a polymer or metal which defines a through bore  270  through which piston rod  64  extends. A jounce bumper nose retaining feature  272  in the form of a plurality of grooves  274  which form a plurality of annular ridges or teeth  276  extends around through bore  170  and extends in a direction facing or toward elastomeric jounce bumper  50 . Jounce bumper cap  254  defines an interface surface  278  which extends radially outward from jounce bumper nose retaining feature  272 . During compression of elastomeric jounce bumper  50 , interface surface  278  defines a stop for elastomeric jounce bumper  50  which causes the compression of elastomeric jounce bumper  50 . The end of jounce bumper cap  254  opposite to interface surface  278  defines an engagement surface which is configured to mate with the outer surface of upper end cap  80 . 
     During a compression stroke for shock absorber  30 , when shock absorber  30  nears its fully compressed condition, nose  178  of elastomeric jounce bumper  50  will first contact jounce bumper retaining feature  272 . Further compression of shock absorber  30  will cause jounce bumper nose retaining feature  272  to locally compress nose  178  and nose  178  will eventually engage interface surface  278 . Further compression of shock absorber  30  will cause further compression of elastomeric jounce bumper  50  and further engagement with interface surface  278 . Jounce bumper nose retaining feature  272  provides a retaining function which reduces or eliminates any radial movement of elastomeric jounce bumper  50  with respect to interface surface  278  of jounce bumper cap  254  to eliminate any noise generation generated by the sliding motion of elastomeric jounce bumper  50  along interface surface  278 . 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Technology Category: b