Abstract:
A valve for controlling fluid flow through a passage defined by a valve body or a piston includes a valve disc which abuts the valve body or the piston. The valve body or the piston defines a first supporting member for the valve disc, a second supporting member for the valve disc located radially inward from the first supporting member and a third supporting member for the valve disc located between the first and second supporting members. This valve disc abuts the first and second supporting members and a clearance is defined between the valve disc and the third supporting member.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to shock absorbers having a unique check valve assembly for use with a base valve assembly or a piston valve assembly. More particularly, the present invention relates to a shock absorber having a check valve assembly which includes an additional support land on the valve body to support and protect a valve disc against damage due to high fluid pressures.  
       BACKGROUND OF THE INVENTION  
       [0002]     Shock absorbers are used in conjunction with automotive suspension systems and other suspension systems to absorb unwanted vibrations which occur during movement of the suspension system. In order to absorb these unwanted vibrations, automotive shock absorbers are generally connected between the sprung (body) and the unsprung (suspension/chassis) masses of the vehicle.  
         [0003]     The most common type of shock absorbers for automobiles is the dashpot type which can be either a mono-tube design or a dual-tube design. In the mono-tube design, a piston is located within a pressure tube and is connected to the spring mass of the vehicle through a piston rod. The pressure tube is connected to the unsprung mass of the vehicle. The piston divides the pressure tube into an upper working chamber and a lower working chamber. The piston includes compression valving which limits the flow of damping fluid from the lower working chamber during a compression stroke and rebound valving which limits the flow of damping fluid from the upper working chamber to the lower working chamber during a rebound or extension stroke. Because the compression valving and the rebound valving have the ability to limit the flow of damping fluid, the shock absorber is able to produce a damping force which counteracts the vibrations which would otherwise be transmitted from the unsprung mass to the sprung mass.  
         [0004]     In a dual-tube shock absorber, a fluid reservoir is defined between the pressure tube and a reservoir tube which is positioned around the pressure tube. A base valve assembly is located between the lower working chamber and the fluid reservoir to control the flow of dampening fluid. The compression valving of the piston is moved to the base valve assembly and is replaced by a compression check valve assembly. In addition to the compression valving, the base valve assembly includes a rebound check valve assembly. The compression valving of the base valve assembly produces the damping force during a compression stroke, and the rebound valving of the piston produces the damping force during a rebound or extension stroke. Both the compression and rebound check valve assemblies permit fluid flow in one direction, but prohibit fluid flow in an opposite direction; however, they are designed such that they do not generate a damping force.  
         [0005]     In applications where a low level of flow restriction is a priority for the check valve assemblies, the working surface for lifting the check valve disc must be maximized. In addition, this low flow restriction level also calls for a very lightweight disc. When first reviewing the design for the check valve assembly, it may seem logical to utilize a valve spring, which has a low stiffness. This design choice is overruled by the need for a fast closing check valve assembly, as well as the need to avoid “chuckle” noise when the shock absorber is mounted on the vehicle.  
         [0006]     As the check valve disc becomes lighter and thinner, and the area of the check valve disc which is acted upon by fluid pressure becomes greater, the check valve disc becomes very sensitive to the high fluid pressure which urges the check valve assembly into its closed position.  
         [0007]     The continued development of check valve assemblies has been directed towards reducing the level of flow restriction without compromising the sensitivity of the check valve assembly to the high pressure fluid which urges the check valve assembly into its closed position.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides the art with a valve body which includes a third land that supports the check valve disc. The third land is designed to distribute the load from the high pressure fluid over three, instead of two, lands to reduce the unsupported span of the disc. In order to maximize the working surface which reacts to open the check valve assembly, a clearance is provided between the third land and the check valve disc.  
         [0009]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]      FIG. 1  is a schematic representation of a typical automobile which incorporates the unique base valve assembly in accordance with the present invention;  
         [0012]      FIG. 2  is a side sectional view of the shock absorber in accordance with the present invention;  
         [0013]      FIG. 3  is an enlarged cross-sectional view of the piston assembly in accordance with the present invention;  
         [0014]      FIG. 4  is an enlarged view of the compression check valve assembly shown in  FIG. 3 ;  
         [0015]      FIG. 5  is an enlarged cross-sectional view of the base valve assembly in accordance with the present invention; and  
         [0016]      FIG. 6  is an enlarged view of the rebound check valve assembly shown in  FIG. 5 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0018]     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in  FIG. 1 a  vehicle incorporating a suspension system incorporating the unique shock absorbers 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  of vehicle  10 . The rear axle assembly is operatively connected to body  16  by means of a pair of shock absorbers  20  and a pair of helical coil springs  22 . Similarly, front suspension  14  includes a transversely extending front axle assembly (not shown) to operatively support a pair of front wheels  24  of vehicle  10 . The front axle assembly is operatively connected to body  16  by means of a second pair of shock absorbers  26  and by a pair of helical coil springs  28 . Shock absorbers  20  and  26  serve to dampen the relative motion of the unsprung mass (i.e., front and rear suspensions  12  and  14 , respectively) and the sprung mass (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 such as vehicles incorporating independent front and/or independent rear suspension systems. Further, the term “shock absorber” as used herein is meant to refer to dampers in general and thus will include MacPherson struts.  
         [0019]     Referring now to  FIG. 2 , shock absorber  20  is shown in greater detail. While  FIG. 2  illustrates only shock absorber  20 , it is to be understood that shock absorber  26  also includes the base valve assembly described below for shock absorber  20 . Shock absorber  26  only differs from shock absorber  20  in the manner in which it is adapted to be connected to the sprung and unsprung masses of vehicle  10 . Shock absorber  20  comprises a pressure tube  30 , a piston assembly  32 , a piston rod  34 , a reservoir tube  36  and a base valve assembly  38 .  
         [0020]     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 upper end cap  50  which closes the upper end of pressure tube  30 . A sealing system seals the interface between upper end cap  50 , reservoir tube  36  and piston rod  34 . The end of piston rod  34  opposite to piston assembly  32  is adapted to be secured to the sprung portion of vehicle  10 . Valving within piston assembly  32  controls the movement of fluid between upper working chamber  44  and lower working chamber  46  during movement of piston assembly  32  within pressure tube  30 . Because piston rod  34  extends only through upper working chamber  44  and not lower working chamber  46 , movement of piston assembly  32  with respect to pressure tube  30  causes a difference in the amount of fluid displaced in upper working chamber  44  and the amount of fluid displaced in lower working chamber  46 . The difference in the amount of fluid displaced is known as the “rod volume” and it flows through base valve assembly  38 .  
         [0021]     Reservoir tube  36  surrounds pressure tube  30  to define a fluid reservoir chamber  52  located between tubes  30  and  36 . The bottom end of reservoir tube  36  is closed by an end cap  54  which is adapted to be connected to the unsprung portion of vehicle  10 . The upper end of reservoir tube  36  is attached to upper end cap  50 . Base valve assembly  38  is disposed between lower working chamber  46  and reservoir chamber  52  to control the flow of fluid between chambers  46  and  52 . When shock absorber  20  extends in length, an additional volume of fluid is needed in lower working chamber  46  due to the “rod volume” concept. Thus, fluid will flow from reservoir chamber  52  to lower working chamber  46  through base valve assembly  38  as detailed below. When shock absorber  20  compresses in length, an excess of fluid must be removed from lower working chamber  46  due to the “rod volume” concept. Thus, fluid will flow from lower working chamber  46  to reservoir chamber  52  through base valve assembly  38  as detailed below.  
         [0022]     Referring now to  FIG. 3 , piston assembly  32  comprises a valve body  60 , a compression check valve assembly  62  and a rebound valve assembly  64 . Compression check valve assembly  62  is assembled against a shoulder  66  on piston rod  34 . Valve body  60  is assembled against compression check valve assembly  62  and rebound valve assembly  64  is assembled against valve body  60 . A nut  68  secures these components to piston rod  34 .  
         [0023]     Valve body  60  defines a plurality of compression passages  70  and a plurality of rebound passages  72 . Seal  48  includes a plurality of ribs  74  which mate with a plurality of annular grooves  76  to permit sliding movement of piston assembly  32 .  
         [0024]     Compression check valve assembly  62  comprises a retainer  78 , a valve disc  80  and a spring  82 . Retainer  78  abuts shoulder  66  on one end and valve body  60  on the other end. Valve disc  80  abuts valve body  60  and closes compression passages  70  while leaving rebound passages  72  open. Spring  82  is disposed between retainer  78  and valve disc  80  to bias valve disc  80  against valve body  60 . During a compression stroke, fluid in lower working chamber  46  is pressurized causing fluid pressure to react against valve disc  80 . When the fluid pressure against valve disc  80  overcomes the biasing load of spring  82 , valve disc  80  separates from valve body  60  to open compression passages  70  and allow fluid flow from lower working chamber to upper working chamber. Typically spring  82  only exerts a light load on valve disc  80 , and it does not contribute to the damping characteristics for shock absorber  20 . The damping characteristics for shock absorber  20  are controlled by base valve assembly  38  which accommodates the flow of fluid from lower working chamber  46  to reservoir chamber  52  due to the “rod volume” concept as detailed below. During a rebound stroke, compression passages  70  are closed by valve disc  80 .  
         [0025]     Rebound valve assembly  64  comprises a spacer  84 , a plurality of valve discs  86 , a retainer  88  and a Belleville spring  90 . Spacer  84  is threadingly received on piston rod  34  and is disposed between valve body  60  and nut  68 . Spacer  84  retains valve body  60  and compression check valve assembly  62  while permitting the tightening of nut  68  without compressing either valve disc  80  or valve discs  86 . Retainer  78 , valve body  60  and spacer  84  provide a continuous solid connection between shoulder  66  and nut  68  to facilitate the tightening and securing of nut  68  to spacer  84  and thus to piston rod  34 . Valve discs  86  are slidingly received on spacer  84  and abut valve body  60  to close rebound passages  72  while leaving compression passages  70  open. Retainer  88  is also slidingly received on spacer  84  and it abuts valve discs  86 . Belleville spring  90  is assembled over spacer  84  and is disposed between retainer  88  and nut  68  which is threadingly received on spacer  84 . Belleville spring  90  biases retainer  88  against valve discs  86  and valve discs  86  against valve body  60 . The plurality of valve discs  86  comprise a bleed disc  92 , a valve disc  94 , a spacer disc  96  and a fulcrum disc  98 . Bleed disc  92  includes at least one slot  100  which permits a limited amount of bleed flow bypassing rebound valve assembly  64 . Fulcrum disc  98  provides a fulcrum or bending point for bleed disc  92 , valve disc  94  and spacer disc  96 . When fluid pressure is applied to discs  92  and  94 , they will elastically deflect at the outer peripheral edge of spacer disc  96  and fulcrum disc  98  to open rebound valve assembly  64 . A shim  102  is located between nut  68  and Belleville spring  90  to control the preload for Belleville spring  90  and thus the blow off pressure as described below. Thus, the calibration for the blow off feature of rebound valve assembly  64  is separate from the calibration for compression check valve assembly  62 .  
         [0026]     During a rebound stroke, fluid in upper working chamber  44  is pressurized causing fluid pressure to react against valve discs  86 . When the fluid pressure reacting against valve discs  86  overcomes the bending load for valve discs  86 , valve discs  86  elastically deflect opening rebound passages  72  allowing fluid flow from upper working chamber  44  to lower working chamber  46 . The strength of valve discs  86  and the size of rebound passages  72  will determine the damping characteristics for shock absorber  20  in rebound. Prior to the deflection of valve discs  86 , a controlled amount of fluid flows from upper working chamber  44  to lower working chamber  46  through slot  100  to provide low speed tunability. When the fluid pressure within upper working chamber  44  reaches a predetermined level, the fluid pressure will overcome the biasing load of Belleville spring  90  causing axial movement of retainer  88  and the plurality of valve discs  86 . The axial movement of retainer  88  and valve discs  86  fully opens rebound passages  72  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  20  and/or vehicle  10 .  
         [0027]     Referring now to  FIGS. 3 and 4 , compression check valve assembly  62  is designed to provide a low restriction to the flow of fluid from lower working chamber  46  to upper working chamber  44 , and it is designed to maximize the working surface for lifting valve disc  80 . Valve body  60  defines a first or outer land  104 , a second or inner land  106 , and a third or intermediate land  108 . Valve disc  80  is biased by spring  82  against outer land  104  and inner land  106 . A clearance is provided between intermediate land  108  and valve disc  80 . In the preferred embodiment, this clearance is in the order of magnitude of a tenth of a millimeter. This clearance maximizes the working surface during the compression stroke by allowing fluid pressure in lower working chamber  46  to react against the surface area of valve disc  80  which is between outer land  104  and inner land  106 . This provides for a low level of intake restriction for compression check valve assembly  62 . During a rebound stroke, fluid pressure within upper working chamber  44  reacts against the upper surface of valve disc  80 . Due to valve disc  80  being designed thin to reduce its weight, valve disc  80  will deflect in the area between outer land  104  and inner land  106  to contact intermediate land  108 , which provides additional support for valve disc  80 . Intermediate land  108  supports valve disc  80  during the rebound stroke to minimize the unsupported span of valve disc  80  by distributing the load over all three lands  104 ,  106  and  108 .  
         [0028]     Referring now to  FIG. 5 , base valve assembly  38  comprises a valve body  120 , an intake or rebound check valve assembly  122 , a compression valve assembly  124 , a retaining bolt  126  and a retaining nut  128 . Valve body  120  is secured to pressure tube  30  and end cap  54  by press fitting or by other methods known well in the art. End cap  54  is secured to reservoir tube  36  and it defines a plurality of fluid passages  130  which allow communication between reservoir chamber  52  and base valve assembly  38 . Valve body  120  defines a plurality of intake or rebound fluid passages  132 , a plurality of compression passages  134  and a central bore  138 . Retaining bolt  126  extends through central bore  138  and threadingly engages retaining nut  128  to secure both intake valve assembly  122  and compression valve assembly  124  to valve body  120 .  
         [0029]     Rebound check valve assembly  122  comprises a valve disc  140  and a valve spring  142 . Valve disc  140  is an annular member which defines an internal bore for allowing fluid flow to reach compression passages  134 . Valve disc  140  is biased against the upper surface of valve body  120  by valve spring  142  which is located between valve disc  140  and retaining nut  128 . Valve disc  140  closes the plurality of rebound fluid passages  132 . During a rebound stroke of shock absorber  20 , fluid pressure decreases in lower working chamber  46  until the fluid pressure within reservoir chamber  52  and intake fluid passages  132  is capable of overcoming the biasing force of valve spring  142 . When the biasing force exerted by valve spring  142  is exceeded by fluid pressure acting against valve disc  140 , valve disc  140  is moved away from valve body  120  to allow fluid flow from reservoir chamber  52  to lower working chamber  46 .  
         [0030]     Compression valve assembly  124  comprises one or more mid/high speed valve discs  150 , one ported restriction discs  152  and one or more variable orifice bleed discs  154 . Discs  150 ,  152  and  154  are stacked together and located adjacent to valve body  120  with mid/high speed valve disc  150  abutting valve body  120 , ported restriction disc  152  abutting mid/high speed valve disc  150  and variable orifice bleed disc  154  abutting ported restriction disc  152 . Discs  150 ,  152  and  154  are held in position by being sandwiched between a shoulder  156  located on retaining bolt  126  and the lower surface of valve body  120 . Retaining bolt  126  is secured to valve body  120  by retaining nut  128 .  
         [0031]     During a compression stroke, fluid pressure increases in lower working chamber  46  and this fluid pressure reacts against valve discs  150 ,  152  and  154 . Fluid pressure builds up in lower working chamber  46  and this fluid pressure in lower working chamber  46  acts against valve disc  150  and valve disc  154 . A low speed oil flow circuit will open when this fluid pressure overcomes the load necessary to deflect disc valve  154  and allow fluid flow between lower working chamber  46  and reservoir chamber  52 . Once the low speed oil flow circuit is saturated by fluid flow rate, fluid pressure continues to build up in lower working chamber  46  until the pressure acting against the mid/high speed valve discs  150  overcomes the load required to deflect discs  150  and allow fluid flow from lower working chamber  46  to reservoir chamber  52 .  
         [0032]     Referring now to  FIGS. 5 and 6 , rebound check valve assembly  122  is designed to provide a low restriction to the flow of fluid from reservoir chamber  52  to lower working chamber  46 , and it is designed to maximize the working surface for lifting valve disc  140 . Valve body  120  defines a first or outer land  174 , a second or inner land  176 , and a third or intermediate land  178 . Valve disc  140  is biased by valve spring  142  against outer land  174  and inner land  176 . A clearance is provided between intermediate land  178  and valve disc  140 . In the preferred embodiment, this clearance is in the order of magnitude of a tenth of a millimeter. This clearance maximizes the working surface during the rebound stroke by allowing fluid pressure in reservoir chamber  52  to react against the surface are of valve disc  140  which is between outer land  174  and inner land  176 . This provides for a low level of intake restriction for rebound check valve assembly  122 . During a compression stroke, fluid pressure within lower working chamber  46  reacts against the upper surface of valve disc  140  and, due to valve disc  140  being designed thin to reduce its weight, valve disc  140  will deflect in the area between outer land  174  and inner land  176  to contact intermediate land  178 , which provides additional support for valve disc  140 . Intermediate land  178  supports valve disc  140  during the rebound stroke to minimize the unsupported span of valve disc  140  by distributing the load over all three lands  174 ,  176  and  178 .  
         [0033]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.