Abstract:
Contact noise generated between a striker cap mounted on a strut and a jounce bumper connected to a shock tower is reduced by providing an axial projection on the roof of the striker cap. The projection progressively displaces and compresses the elastomeric jounce bumper material and thereby avoids large compressive impulse forces and associated noise generation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a jounce bumper and coacting striker cap for absorbing shock forces between a vehicle body and a vehicle suspension system and in particular to a striker cap bumper which fits over the end of a strut and is shaped to reduce impact noise. 
     2. Description of Prior Developments 
     A rubber or elastomeric jounce bumper is typically mounted between a vehicle body (or strut mount attached to the body) and a shock absorbing member such as a suspension strut to prevent metal-to-metal contact during severe jounce travel. A cover or striker cap may be provided between the end of the strut and the jounce bumper to protect the end of the strut and the strut seal from damage during such extreme jounce movements. 
     Although prior jounce bumper and striker cap assemblies have performed satisfactorily, they tend to produce a relatively large noise upon mutual engagement and impact during jounce movements. In some cases, where the jounce bumper is mounted relatively close to an occupant of the vehicle, the impact noise can become so loud as to be annoying and generally unacceptable. 
     Accordingly, a need exists for a jounce bumper and striker cap assembly which operates quietly and effectively. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed to fulfill the needs noted above and, therefore, has as an object the provision of a striker cap and jounce bumper assembly that operates quietly and effectively without adding significant cost to the assembly or substantially changing the design. The invention is focused on a specially contoured striker cap which includes an axial projection of limited surface area which makes first contact with the jounce bumper. The cross-section of the projection preferably decreases in the axial direction toward the jounce bumper so that a gradual and progressive contact and displacement area develops between the striker cap and jounce bumper during severe jounce movement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic view, partly in section, of a vehicle suspension system provided with a striker cap constructed in accordance with the invention; 
     FIG. 2 is a view of FIG. 1 showing the suspension system in a severe jounce position with the striker cap abutted against the jounce bumper; 
     FIG. 3 is a top perspective view of the striker cap of FIGS. 1 and 2; and 
     FIG. 4 is a view in section taken through line  4 — 4  of FIG.  3 . 
    
    
     In the drawings, like reference numerals denote like or similar parts. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in conjunction with the drawings, beginning with FIG. 1 which shows a vehicle suspension system  10  of the type used to mount a rear tire  12  to a vehicle. A pivoting lateral link  14  interconnects the tire wheel to a cross bar  16  which forms a portion of a vehicle frame or chassis. A strut  18  interconnects the tire wheel to a shock tower  20  formed on the body of a vehicle. 
     A stabilizer bar  22  extends between the vehicle chassis and the strut  18  to further support the strut and rear tire. A coil spring  24  is mounted between the shock tower  20  and strut  18  to absorb shocks transmitted between the tire  12  and vehicle body. A jounce bumper  26  is mounted between the shock tower  20  and the top end  28  of the strut cylinder  30 . 
     A striker cap  32 , formed of hard molded plastic is press fit over the top end  28  of strut cylinder  30 . Cap  32  acts primarily as a protective cover for strut seal  34  which maintains damping fluid under pressure within cylinder  30 . As seen in FIGS. 3 and 4, a circular array of axially-extending ridges  36  is formed on the inner surface of the cylindrical tubular side wall  38  of the cap  32 . Ridges  36  include a ramped wedge-like lower end portion  40  for initiating and facilitating the tight press-fit of cap  32  on cylinder  30 . 
     Cap  32  further includes a roof  42  having a central aperture  44  formed therethrough so as to define a generally annular abutment and engagement surface supported by the side wall  38 . A projection or bumper  46  extends axially outwardly and upwardly from roof  42  for making initial contact with the jounce bumper  26 . 
     Bumper  46  is formed as a pair of arched ridges extending diametrically across roof  42  on opposite sides of aperture  44 . The cross-sectional area of the projecting ridges decreases from the roof  42  toward the jounce bumper  26  to provide a gradual increase in contact area between the cap and jounce bumper. 
     A serrated or spoked support skirt  48  extends radially outwardly around the lower edge  50  of side wall  38 . Skirt  48 , as defined by an annular series of flanges  52 , provides support surfaces for the lower axial end face  54  of dust shield or bellows  56 . This support maintains the bellows  56  in a generally centered position around the striker cap  32  as well as around piston rod  58  and within coil spring  54 , thereby preventing rubbing wear and noise between the bellows  56 , cap  32 , and coil spring  24 . 
     In use, as the suspension system  10  moves from its relatively unloaded position in FIG. 1 to its severely loaded position in FIG. 2, the striker cap  32  engages and axially compresses the jounce bumper  26 . During this compression, the bumper  46  on cap  32  progressively embeds itself within the elastomeric material of the jounce bumper  26 . As seen in FIG. 4, the arched shape of bumper  46  will gradually compress the material of the jounce bumper  26  while displacing more and more volume of the material of bumper  26  until the roof of cap  32  contacts the bumper  26 . 
     Because of this gradual dissipation of energy between the jounce bumper  26  and the striker cap  32 , loud contact noises are reduced due to the decreased impulse of contact forces therebetween. In tests, such contact noises have been reduced by 75% using a striker cap with an axially-extending bumper  46  as compared to using a flat-roofed striker cap which makes substantially full initial contact with a jounce bumper  26 . 
     Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than specifically described.