Abstract:
A shock absorber includes a piston assembly disposed within a pressure tube. The piston assembly has a first and a second housing and a valve assembly located adjacent the first housing. The valve assembly has a valve disc which engages the first housing to close at least one of a first plurality of passages extending through the first and second housings and a biasing member for applying a load to the valve disc.

Description:
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 shock absorber having a full displacement valve assembly to control fluid flow. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Shock absorbers are used in conjunction with automotive suspension systems to absorb unwanted vibrations which occur during driving. Shock absorbers are generally connected between the sprung portion (body) and the unsprung portion (wheels) of the automobile. In a monotube shock absorber, a piston is located within a working chamber defined by a pressure tube of the shock absorber, with the piston being connected to the sprung portion of the automobile through a piston rod. The pressure tube is connected to the unsprung portion of the vehicle by one of the methods known in the art. Because the piston is able, through valving, to limit the flow of damping fluid between opposite sides of the piston when the shock absorber is compressed or extended, the shock absorber is able to produce a damping force which damps the unwanted vibration which would otherwise be transmitted between the unsprung portion and the sprung portion of the automobile. 
     In a dual tube shock absorber, a piston is located within a working chamber defined by a pressure tube of the shock absorber, with the piston being connected to the sprung portion of the automobile through a piston rod. A reserve tube surrounds the pressure tube to define a reserve chamber with a base valve assembly being located between the working chamber and the reserve chamber. The reserve tube is connected to the unsprung portion of the vehicle by one of the methods known in the art. Valving in the piston limits the flow of damping fluid between an upper side and a lower side of the piston when the shock absorber is extended to create a damping load. Valving in the base valve assembly limits the flow of damping fluid between the working chamber and the reserve chamber when the shock absorber is compressed to create a damping load. The piston also includes a check valve for replenishment of fluid on the upper side of the piston during a compression stroke and the base valve assembly includes a check valve for replenishment of fluid on the lower side of the piston during an extension stroke. 
     SUMMARY 
     A shock absorber piston typically has at least one fluid control valve assembly. The fluid control valve assembly includes a valve disc which moves axially with respect to the piston body to fully open the fluid passage. The fluid control assembly can be used as a compression valve assembly and/or as a rebound valve assembly for either the piston assembly and/or a base valve assembly. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples 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 illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is an illustration of an automobile having shock absorbers which incorporate the piston design in accordance with the present invention; 
         FIG. 2  is a side view, partially in cross-section of a shock absorber from  FIG. 1  which incorporates the piston design in accordance with the present invention; 
         FIG. 3  is an enlarged side view, partially in cross-section, of the piston assembly from the shock absorber illustrated in  FIG. 2 ; 
         FIG. 4  is a cut-away perspective view of the piston illustrated in  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of the piston illustrated in  FIG. 3 ; 
         FIG. 6  is a plan view of the tuning disc illustrated in  FIGS. 3-5 ; 
         FIGS. 7A-7C  are perspective views of various embodiments of the interface discs illustrated in  FIGS. 2 and 3 ; 
         FIG. 8  is an enlarged side view, partially in cross section, of a piston assembly in accordance with another embodiment of the invention; and 
         FIG. 9  is a perspective view of various embodiments of the interface discs illustrated in  FIGS. 2 and 3 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. There is shown in  FIG. 1  a vehicle incorporating a suspension system having shock absorbers, each of which incorporates a piston assembly in accordance with the present invention, and which is designated generally by the reference numeral  10 . Vehicle  10  includes 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 a pair of rear wheels  18 . The rear axle is attached to body  16  by means of a pair of shock absorbers  20  and by a pair of springs  22 . Similarly, front suspension  14  includes a transversely extending front axle assembly (not shown) to operatively support a pair of front wheels  24 . The front axle assembly is attached to body  16  by means of a pair of shock absorbers  26  and by a pair of springs  28 . Shock absorbers  20  and  26  serve to dampen the relative motion of the unsprung portion (i.e., front and rear suspensions  12 ,  14 ) with respect to 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  20  and  26  may be used with other types of vehicles or in other types of applications including, but not limited to, vehicles incorporating non-independent front and/or non-independent rear suspensions, vehicles incorporating independent front and/or independent rear suspensions or other suspension systems known in the art. Further, the term “shock absorber” as used herein is meant to refer to dampers in general and thus will include McPherson struts and other damper designs known in the art. 
     Referring now to  FIG. 2 , shock absorber  20  is illustrated in greater detail. While  FIG. 2  illustrates only shock absorber  20 , it is to be understood that shock absorber  26  also includes the multi-piece piston in accordance with the present invention. Shock absorber  26  only differs from shock absorber  20  in the way it is adapted to be connected to the sprung and unsprung portions of vehicle  10 . Shock absorber  20  comprises a pressure tube  30 , a piston assembly  32  and a piston rod  34 . While shock absorber  20  with piston assembly  32  is illustrated as a mono-tube shock absorber, piston assembly  32  can also be utilized in a dual-tube or multi-tube shock absorber. 
     Pressure tube  30  defines a working chamber  42 . Piston assembly  32  is slidably disposed within pressure tube  30  and divides working chamber  42  into an upper working chamber  44  and a lower working chamber  46 . A seal  48  is disposed between piston assembly  32  and pressure tube  30  to permit sliding movement of piston assembly  32  with respect to pressure tube  30  without generating undue frictional forces as well as sealing upper working chamber  44  from lower working chamber  46 . Piston rod  34  is attached to piston assembly  32  and extends through upper working chamber  44  and through an upper end cap or rod guide  50  which closes the upper end of pressure tube  30 . A sealing system  52  seals the interface between rod guide  50 , pressure tube  30  and piston rod  34 . The end of piston rod  34  opposite to piston assembly  32  is adapted to be secure to the sprung portion of vehicle  10 . The end of pressure tube  30  opposite to rod guide  50  is adapted to be connected to the unsprung portion of vehicle  10 . Extension valving of piston assembly  32  controls the movement of fluid between upper working chamber  44  and lower working chamber  46  during an extension movement of piston assembly  32  within pressure tube  30 . Compression valving of piston assembly  32  controls the movement of fluid between lower working chamber  46  and upper working chamber  44  during a compression movement of piston assembly  32  within pressure tube  30 . 
     Referring to  FIGS. 2-6 , piston assembly  32  is illustrated in greater detail. Piston assembly  32  comprises a compression valve assembly  60 , a multi-piece piston body  62  and an extension valve assembly  64 . Piston rod  34  defines a reduced diameter section  66  onto which compression valve assembly  60 , multi-piece piston body  62  and extension valve assembly  64  are located. A nut  68  secures piston assembly  32  onto section  66  of piston rod  34  with compression valve assembly  60  abutting a shoulder located on piston rod  34 , multi-piece piston body  62  abutting compression valve assembly  60 , extension valve assembly  64  abutting multi-piece piston body  62  and nut  68  abutting extension valve assembly  64  and multi-piece piston body  62 . 
     Compression valve assembly  60  comprises a valve disc  72 , an annular housing or interface  74 , one or more biasing members  76 , one or more spacers  78  and a retainer  80 . Valve disc  72 , biasing members  76  and spacers  78  are positioned and/or guided by engagement with retainer  80  as illustrated in  FIG. 3 . Valve disc  72  covers a plurality of compression passages  82  extending into multi-piece piston body  62 . Annular housing  74  abuts the side of valve disc  72  opposite to multi-piece piston body  62 . The one or more biasing members  76  engage annular housing  74  and urge annular housing  74  into engagement with valve disc  72  which urges valve disc  72  against multi-piece piston body  62 . The biasing members  76  are nested within a recess  84  defined by annular housing  74  in order to center and maintain the position of annular housing  74  with respect to multi-piece piston body  62  and piston rod  34 . The one or more spacers  78  are located between the one or more biasing members  76  and retainer  80 . Retainer  80  abuts the shoulder formed by piston rod  34 . Valve disc  72  prevents fluid flow from upper working chamber  44  to lower working chamber  46  but fluid flow from lower working chamber  46  to upper working chamber  44  is allowed due to the unseating of valve disc  72  due to the deflection of the one or more biasing members  76 . 
     Extension valve assembly  64  comprises a valve disc  92 , an annular housing or interface  94 , one or more biasing members  96 , one or more spacers  98  and nut  68 . Valve disc  92 , biasing members  96  and spacers  78  are positioned and/or guided by engagement with nut  68  as illustrated in  FIG. 3 . Valve disc  92  covers a plurality of extension passages  102  extending into multi-piece piston body  62 . Annular housing  94  abuts the side of valve disc  92  opposite to multi-piece piston body  62 . The one or more biasing members  96  engage annular housing  94  and urge annular housing  94  into engagement with valve disc  92  which urges valve disc  92  against multi-piece piston body  62 . The biasing members  96  are nested within a recess  104  defined by annular housing  94  in order to center and maintain the position of annular housing  94  with respect to multi-piece piston body  62  and piston rod  34 . The one or more spacers  98  are located between the one or more biasing members  96  and nut  68 . The position of nut  68  is controlled by a plurality of shims  106  and this determines the biasing load applied by the one or more biasing members  76  and the one or more biasing members  96  and thus the damping characteristics for shock absorber  20  during a compression stroke and an extension stroke. Valve disc  92  prevents fluid flow from lower working chamber  46  to upper working chamber  44  but fluid flow from upper working chamber  44  to lower working chamber  46  is allowed due to the unseating of valve disc  92  due to the deflection of the one or more biasing members  96 . While shims  106  are illustrated as being between retainer  80  and multi-piece piston body  62 , it is within the scope of the present disclosure to have shims  106  disposed between multi-piece piston body  62  and nut  68 . 
     Referring to  FIGS. 3-6 , multi-piece piston body  62  comprises a rebound side housing  110 , a compression side housing  112  and a tuning disc  114 . Rebound side housing  110  defines one or more extension passage inlets  102   a  and one or more compression passage outlets  82   b . Each compression passage outlet  82   b  is surrounded by an island land  82   c . While  FIGS. 3-5  illustrate each compression passage outlet  82   b  as being surrounded by a single island land  82   c , it is within the scope of the present invention to have one or more compression passage outlets  82   b  surrounded by a single island land  82   c . Compression side housing  112  defines a plurality of compression passage inlets  82   a  and a plurality of extension passage outlets  102   b . Each extension passage outlet  102   b  is surrounded by an island land  102   c . While  FIGS. 3-5  illustrate each extension passage outlet  102   b  being surrounded by a single island land  102   c , it is within the scope of the present invention to have one or more extension passage outlets  102   b  surrounded by a single island land  102   c . Tuning disc  114  is disposed between rebound side housing  110  and compression side housing  112  and the shape of tuning disc  114  also determines the damping characteristics for shock absorber  20 . 
     Referring now to  FIG. 6 , tuning disc  114  defines a plurality of compression openings  82   d  and a plurality of extension openings  102   d . When properly assembled, the plurality of compression openings  82   d  align with the plurality of compression passages  82  and the plurality of extension openings  102   d  align with the plurality of extension passages  102 . In order to maintain the alignment of the above openings with their respective passages, various orientation means can be incorporated. A specific assembly tool (not shown) can be used to orient the parts directly followed by a banding process such as the assembly of seal  48 . Seal  48  will act as retaining means and keep the components together in an assembled condition in the correct orientation during handling and assembly of piston assembly  32 . One or more dents  120  can be formed into tuning disc  114 . Dents  120  can be designed to engage one or more holes (now shown) in rebound side housing  110  and one or more holes (not shown) in compression side housing  112  to provide the correct orientation. A slight interference fit can be used between dents  120  and their respective hole to make it possible to further handle piston assembly  32 . In addition, or as a replacement for the interference fit, seal  48  can be utilized to maintain the orientation of the components. 
     During a compression stroke of shock absorber  20 , fluid pressure in lower working chamber  46  increases and fluid pressure in upper working chamber  44  decreases. This difference in fluid pressure reacts against valve disc  72  in a direction that attempts to unseat valve disc  72  from multi-piece piston body  62 . This difference in fluid pressure also reacts against valve disc  92  to urge valve disc  92  into engagement with multi-piece piston body  62 . When the fluid pressure differential increases, valve disc  72  will fully unseat from island lands  82   c  of multi-piece piston body  62  due to the deflection of the one or more biasing members  76  and fluid will flow from lower working chamber  46 , through the plurality of compression passage inlets  82   a , through the plurality of compression openings  82   d , through the plurality of compression passage outlets  82   b , past valve disc  72  and into upper working chamber  44 . 
     The damping characteristics for shock absorber  20  during a compression stroke are determined by the one or more biasing members  76 , and the size of compression openings  82   d.    
     During an extension or rebound stroke of shock absorber  20 , fluid pressure in upper working chamber  44  increases and fluid pressure in lower working chamber  46  decreases. This difference in fluid pressure reacts against valve disc  92  in a direction that attempts to unseat valve disc  92  from multi-piece piston body  62 . This difference in fluid pressure also reacts against valve disc  72  to urge valve disc  72  into engagement with multi-piece piston body  62 . When the fluid pressure differential increases, valve disc  92  will fully unseat from island lands  102   c  of multi-piece piston body  62  due to the deflection of the one or more biasing members  96  and fluid will flow from upper working chamber  44 , through the plurality of extension passage inlets  102   a , through the plurality of extension openings  102   d , through the plurality of extension passage outlets  102   b , past valve disc  92  and into lower working chamber  46 . 
     The damping characteristics for shock absorber  20  during a rebound or extension stroke are determined by the one or more biasing members  96 , and the size of extension openings  102   d.    
     When tuning shock absorber  20 , it may be advantageous to provide a common bleed flow passage  140  which is a passage that is always open in both compression and extension strokes of shock absorber  20 .  FIG. 6  illustrates, in phantom, bleed flow passage  140  which allows fluid flow between upper and lower working chambers  44  and  46  during both compression and rebound strokes of shock absorber  20 . The amount of bleed flow can be controlled by controlling the size and number of bleed flow passages  140 . 
     Thus, multi-piece piston body  62  permits the individual tuning of compression damping, rebound damping and bleed flow by varying the design of tuning disc  114 . This permits different applications to utilize the same rebound side housing  110  and compression side housing  112  with the specific tuning requirements being selected by the design of tuning disc  114 . In addition, additional tuning requirements can be selected by using different biasing members  76  and/or  96  but still with using common side housings  110  and  112 . 
       FIG. 7A  illustrates one embodiment of biasing member  76  and biasing member  96 . Biasing disc  76 ,  96  includes an annular center portion  150  and a plurality of legs  152 . The number and width of legs  152  can be selected to provide the specified damping characteristics for shock absorber  20 . As illustrated in  FIG. 7A , the plurality of legs  152  are all the same width and are located symmetrically around center portion  150 .  FIG. 7B  illustrates a biasing disc  76 ′,  96 ′ where the plurality of legs  152  are not the same width and are not symmetrically located around center portion  150 , thus creating an asymmetric design. This asymmetric design can be used to tune the damping curve for shock absorber  20 .  FIG. 7C  illustrates a biasing disc  76 ″,  96 ″ as an annular full disc without legs  152 . 
     Referring now to  FIG. 8 , a piston assembly  232  is illustrated. Piston assembly  232  comprises a compression valve assembly  260 , multi-piece piston body  62  and an extension valve assembly  264 . A piston rod  234  defines reduced diameter section  66  onto which compression valve assembly  260 , multi-piece piston body  62  and extension valve assembly  264  are located. Piston assembly  232  is secured onto section  66  of piston rod  234  using a riveted end  268  of piston rod  234 . Compression valve assembly  260  abuts a shoulder located on piston rod  234 , multi-piece piston body  62  abuts compression valve assembly  260 , extension valve assembly  264  abuts multi-piece piston body  62  and riveted end  268  abuts extension valve assembly  264 . 
     Compression valve assembly  260  comprises valve disc  72 , an annular housing or interface  274 , the one or more biasing members  76 , the one or more spacers  78  and retainer  80 . Thus, compression valve assembly  260  is the same as compression valve assembly  60  except that compression valve assembly  260  includes annular housing or interface  274 . Interface  274  is guided for axial motion by being piloted on retainer  80 . This allows for the elimination of recess  84  and allows biasing members  76  to simply abut annular housing  274 . The function and operation for compression valve assembly  260  is the same as that discussed above for compression valve assembly  60 . 
     Extension valve assembly  264  comprises valve disc  92 , an annular housing or interface  294 , the one or more biasing member  96 , the one or more spacers  98  and a retainer  80 . Thus, extension valve assembly  264  is the same as extension valve assembly  64  except that extension valve assembly  264  includes annular housing or interface  294  and retainer  80  replaces nut  68  because of riveted end  268  of piston rod  234 . Interface  294  is guided for axial movement by being piloted on retainer  80 . This allows for the elimination of recess  104  and allows biasing members  96  to simply abut annular housing  294 . Riveted end  268  maintains the assembly of piston assembly  232  and it eliminates the threaded connection associated with piston rod  34  and nut  68 . Piston assembly  232  also utilizes shims  106  to control the load exerted by biasing members  76  and  96 . 
     Referring now to  FIG. 9 , a piston assembly  332  is illustrated. Piston assembly  332  comprises compression valve assembly  260 , multi-piece piston body  62  and an extension valve assembly  364 . Piston rod  34  defines reduced diameter section  66  onto which compression valve assembly  260 , multi-piece piston body  62  and extension valve assembly  364  are located. Piston assembly  332  is secured onto section  66  of piston rod  34  using a nut  368 . Compression valve assembly  260  abuts the shoulder on piston rod  34 , multi-piece piston body  62  abuts compression valve assembly  260 , extension valve assembly  364  abuts multi-piece piston body  62  and nut  368  abuts extension valve assembly  364 . 
     Compression valve assembly  260  comprises valve disc  72 , annular housing or interface  274 , the one or more biasing members  76 , the one or more spacers  78  and retainer  80 . Thus, compression valve assembly  260  is the same as compression valve assembly  60  except that compression valve assembly  260  includes annular housing or interface  274 . Interface  274  is guided for axial motion by being piloted on retainer  80 . This allows for the elimination of recess  84  and allows biasing members  76  to simply abut annular housing  274 . The function and operation for compression valve assembly  260  is the same as that discussed above for compression valve assembly  60 . 
     Extension valve assembly  364  comprises a plurality of valve discs  392 , one or more spacers  394  and a retainer  396 . One valve disc  392  covers the plurality of extension passages  102  extending into multi-piece piston body  62 . The one or more spacers  394  abut the side of valve discs  392  opposite to multi-piece piston body  62 . The plurality of valve discs  392 , the one or more spacers  394  and retainer  396  are clamped or sandwiched between multi-piece piston body  62  and nut  368 . Shims  106  control the load being applied by biasing member  76  of compression valve assembly  260 . The damping characteristics for shock absorber  20  during an extension stroke is controlled by the bending or deflection of valve discs  392 . Valve discs  392  prevent fluid flow from lower working chamber  46  to upper working chamber  44  but fluid flow from upper working chamber  44  to lower working chamber  46  is allowed due to the bending or deflection of valve discs  92 . 
     During an extension stroke of shock absorber  20 , fluid pressure in upper working chamber  44  increases and fluid pressure in lower working chamber  46  decreases. This difference in fluid pressure reacts against valve discs  392  in a direction that attempts to bend or deflect valve discs  392 . This difference in fluid pressure also reacts against valve disc  72  of compression valve assembly  260  to urge valve disc  72  into engagement with multi-piece piston body  62 . When the fluid pressure differential increases, valve discs  92  will bend or deflect and fluid will flow from upper working chamber  44 , through the plurality of extension passage inlets  102   a , through the plurality of extension openings  102   d , through the plurality of extension passage outlets  102   b , past valve discs  392  and into lower working chamber  46 .