Abstract:
An air spring assembly, for use on an associated vehicle suspension system having a mounting member and a damping member, includes spaced apart first and second end members. A flexible wall is secured on the first and second end members and defines a spring chamber therebetween. An isolator is supported on and sealingly engages the first end member. The isolator includes and isolator passage sealingly receiving the damping member. The isolator and the first end member at least partially form a first load transmission path such that a damping member load is distributed to the mounting member through the isolator and the first end member. The first end member at least partially forms a second load transmission path such that an air spring load is distributed to the mounting member through the first end member without substantial transmission through the isolator.

Description:
BACKGROUND  
       [0001]     The present novel concept broadly relates to the art of vehicle suspension systems and, more particularly, to an air spring assembly having multiple load transmission paths.  
         [0002]     In known suspension systems, particularly those utilizing spring over damper assemblies, the suspension components are often supported using a mounting arrangement that provides only a single load transmission path. It is well understood that various inputs, loads or forces are commonly associated with vehicle suspensions, including spring and jounce bumper loads which are generally unidirectional and damper loads which are normally bidirectional. Single load path mounting arrangements typically include a bearing element mounted on or within an elastomeric isolator that is secured on a mounting plate. In turn, the mounting plate is attached to the vehicle chassis or body and the loads are transmitted along the single load path through the mounting plate to the vehicle chassis or body. As a result, such single load path mounting arrangements have numerous problems and disadvantages that it is desirable to avoid.  
         [0003]     One such disadvantage is that the elastomeric isolator must be designed to isolate the three primary suspension inputs (spring, damper and jounce bumper inputs), which commonly have significantly different magnitudes, frequencies and can also operate in different directions, as indicated above. For example, it is well understood that the spring and bumper inputs can be substantially greater than the damper inputs, and can, in some cases, exceed the damper inputs by one or more orders of magnitude. Thus, the elastomeric isolator is normally designed to at least partially reduce the transmission of all three inputs. This generally results in a compromise design that is different than the design would be for any one individual input. Unfortunately, the resulting isolator is typically biased away from a high compliance and toward a high stiffness to accommodate the higher loads of the spring and bumper inputs, and to support the entire weight of the vehicle as well. This results in increased harshness of the ride quality of the vehicle and can contribute to a corresponding decrease in passenger comfort.  
         [0004]     Another disadvantage of such single load path mounting arrangements is that the forces of higher magnitude that are applied to the isolator tend to accelerate the degradation of the elastomeric material. As such, it is possible for undesirable characteristics, such as reduced performance of the suspension system, increased component wear and/or increased maintenance and repair costs to result from utilizing such mounting arrangements. Therefore, elastomeric isolators are often made more robust to counteract this potential change in performance, which tends to further stiffen the isolator and undesirably add to ride harshness.  
         [0005]     In an effort to overcome these and other disadvantages, mounting arrangements have been developed that provide multiple load transmission paths for vehicle suspension inputs. However, such known arrangements are primarily used in association with steel coil springs. Those of skill in the art will recognize that in these multiple path mounting arrangements, the spring and damping member typically move independently of one another. In suspension systems that utilize coil springs, this does not normally present an issue. However, establishing and reliably maintaining a fluid-tight seal between suspension components that are capable of independent movement is considerably more challenging and can result in the generation of leak paths, component wear and other undesirable performance problems and/or losses. As such, suspension systems using air springs have heretofore been relegated to the use of single load path mounting arrangements in which the air spring and damper move in relative unison with one another and such losses and other disadvantages are more easily overcome.  
       BRIEF DESCRIPTION  
       [0006]     An exemplary embodiment of an air spring assembly in according with the present novel concept, for use on an associated vehicle suspension system that includes a mounting member and a damping member, is provided and includes spaced apart first and second end members. A flexible wall is secured on the first and second end members and defines a spring chamber therebetween. An isolator is supported on and sealingly engages the first end member. The isolator includes an isolator passage sealingly receiving the damping member. The isolator and the first end member at least partially form a first load transmission path such that a damping member load is distributed to the mounting member through the isolator and the first end member. The first end member at least partially forms a second load transmission path such that an air spring load is distributed to the mounting member without substantial transmission through the isolator.  
         [0007]     An exemplary embodiment of an air spring and damper assembly in accordance with the present novel concept, for use on an associated vehicle having first and second suspension mounting members in spaced relation to one another, is provided and includes a damping member having first and second opposing ends. The first end of the damping member is supported on the first suspension mounting member. An air spring is secured along the damping member and includes a first end member, a second end member in spaced relation to the first end member, and a flexible wall secured on the first and second end members and at least partially forming a spring chamber therebetween. The first end member is supported on the damping member toward the first end thereof. An isolator is supported on and sealingly engages the second end member. The second end member is secured on the second suspension mounting member and at least partially forms a first load transmission path therewith such that a load on said air spring is transmitted to the second suspension mounting member through the second end member without substantial transmission through the isolator. The isolator receives and sealingly engages the second end of the damping member. The isolator at least partially forms a second load transmission path to the second suspension mounting member through the second end member such that a damping member load is transmitted to the second suspension mounting member through the isolator and the second end member.  
         [0008]     An exemplary embodiment of an spring and damper assembly in accordance with the present novel concept, for use on an associated vehicle having first and second suspension mounting members in spaced relation to one another, is provided and includes a damping member and a spring assembly. The damping member includes first and second opposing ends. The first end of the damping member is supported on the first suspension mounting member. The spring assembly is secured along the damping member and includes a first support member and a second support member in spaced relation to the first support member. A flexible spring element is supported therebetween. The first support member is secured on the damping member toward the first end thereof. A bumper is disposed along the damping member, and an isolator is supported on and sealing engages the second support member and the damping member. The second support member is secured on the second suspension mounting member and at least partially forms a first load transmission path therewith such that a load on said spring element and a load on said bumper are each transmitted to the second suspension mounting member through the second end member without substantial transmission through the isolator. The isolator at least partially forming a second load transmission path to the second suspension mounting member through the second end member such that a load on the damping member is transmitted to the second suspension mounting member through the isolator and the second end member.  
         [0009]     An exemplary embodiment of an air spring assembly in accordance with the present novel concept, for use on an associated vehicle suspension system having an associated damping member and an associated vehicle mounting structure, is provided and includes spaced apart first and second end members and a flexible wall secured on the first and second end members. An isolator is supported on and sealingly engages the first end member, and is adapted for operative use with the associated damping member. A compliant-member load transmission path extends along at least a portion of the isolator and the first end member such that a damping member load is distributed therealong toward the associated vehicle mounting structure. A rigid-member load transmission path extends along at least a portion of the first end member such that an air spring load is distributed therealong toward the associated vehicle mounting structure without substantial transmission through the isolator. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a top plan view of one embodiment of an air spring and damper assembly in accordance with the present novel concept.  
         [0011]      FIG. 2  is a cross-sectional side view of the air spring and damper assembly in  FIG. 1  taken along  2 - 2 .  
         [0012]      FIG. 3  is a load transmission path diagram superimposed on the cross-sectional side view of  FIG. 2 .  
         [0013]      FIG. 4  is a cross-sectional side view of an alternate embodiment of an air spring assembly in accordance with the present novel concept.  
         [0014]      FIG. 5  is a cross-sectional side view of another alternate embodiment of an air spring assembly in accordance with the present novel concept. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Turning now to the drawings wherein the showings are for the purposes of illustrating exemplary embodiments of the present novel concept only and not for the purposes of limiting the same,  FIGS. 1 and 2  illustrate an air spring and damper assembly  100  including an air spring  102  and a damping member  104 . Air spring  102  includes a first end member, such as a top cap  106 , for example, a second end member, such as a piston  108 , for example, spaced from the first end member and a flexible spring member, such as a flexible sleeve  110 , for example, supported between the end members. In one exemplary embodiment, flexible sleeve  110  can be secured along the spaced end members using retaining members, such as crimp rings  112 , for example. A spring chamber  114  is formed within sleeve  110  between the end members. Air spring  102  is shown and described herein as being a rolling lobe-type air spring. However, it will be appreciated that any other suitable type of air spring could alternately be used, such as a convoluted-type air spring, for example.  
         [0016]     Damping member  104  includes an elongated tubular housing  116  and a damping rod  118  that extends therefrom. It will be appreciated that any suitable type, kind and/or configuration of damper can be used, and that in the exemplary embodiment shown in  FIG. 2 , damping member  104  is a MacPherson strut of substantially conventional construction. Piston  108  of air spring  102  is supported on housing  116  and can be secured thereto in any suitable manner, such as by using fasteners (not shown) or a welded joint (not shown), for example. A jounce bumper  120  is disposed along damping rod  118  within spring chamber  114  and is of a standard construction. The jounce bumper includes an inner wall  122  forming a passage (not numbered) therethrough and an end wall  124  disposed adjacent top cap  106 .  
         [0017]     Top cap  106  includes an outer radial wall  126  along which flexible side wall  110  is secured. A web portion  128  connects outer radial wall  126  with a central wall  130 . Web portion  128  includes a bottom surface  132  disposed toward spring chamber  114 , and end wall  124  of bumper  120  is disposed adjacent bottom surface  132 . Central wall  130  projects outwardly from web portion  128  in a direction generally opposite bottom surface  132 . A passage  134  is formed through top cap  106  by passage walls  136  and  138 . Passage wall  138  is radially outwardly stepped to form an annular shoulder  140  within passage  134 . Additionally, a plurality of radially outwardly extending grooves  142  can optionally be provided along passage  138 .  
         [0018]     An isolator  144  is received within passage  134  and includes an inner sleeve  146  (also known in the art as inner metal), an outer sleeve  148  (also known in the art as outer metal) and elastomeric material  150  disposed therebetween. It will be appreciated that isolating devices, such as isolator  144 , for example, are well known and commonly used in a wide variety of applications and environments. The design and construction of such isolating devices is well known by those of skill in the art. As such, it is to be understood that any suitable type, kind and/or construction of isolator can be used without departing from the principles of the present novel concept.  
         [0019]     Central wall  130  includes a plurality of threads (not numbered) extending along an outer threaded portion  152  thereof, and an insert cap  154  includes an inner threaded wall  156  and an end wall  158  having a passage  160  formed therethrough. Insert cap  154  threadably engages central wall  130  to capture outer sleeve  148  between shoulder  140  and end wall  158 . A fluid-tight seal is formed between outer sleeve  148  and passage wall  138 , such as by disposing a sealing member therebetween. Alternately, outer sleeve  148  can be omitted and elastomeric material  150  can be directly molded on or otherwise sealingly attached to passage wall  138 . As shown in  FIG. 2 , o-rings  162  are received in grooves  142  and form a substantially fluid-tight seal between outer sleeve  148  and passage wall  138 . It will be appreciated, however, that any other suitable manner of sealingly engaging isolator  144  and central wall  130  can be used, such as by using a quad-ring, a lip seal, an adhesive compound and/or a sealant, for example, alone or in combination with one another.  
         [0020]     Damping rod  118  extends into and through passage  134  of top cap  106  and engages isolator  144 . Inner sleeve  146  defines an isolator passage  164 , and damping rod  118  extends therethrough and sealingly engages inner sleeve  146  in a suitable manner, as discussed above. Damping rod  118  includes a radially inwardly stepped annular shoulder  166  and a threaded end  168  generally opposite housing  116 . Additionally, radially inwardly extending grooves  170  can optionally be provided along damping rod  118  and can be used to receive suitable sealing members, such as o-rings  171 , for example. The damping rod extends through passage  164  such that threaded end  168  projects outwardly therefrom. A jounce washer  172  is received on damping rod  118  and engages shoulder  166 . A rebound washer  174  is disposed along threaded end  168  and secured thereon by a threaded nut  176 . Inner sleeve  146  is captured between washers  172  and  174  thereby securing isolator  144  on damping rod  118 .  
         [0021]     A bearing  178  is secured along an exterior wall portion  180  of central wall  130  and can be secured therealong in a suitable manner. For example, in  FIG. 2 , an inner race (not shown) of bearing  178  is captured between a shoulder (not numbered) on central wall  130  and a retaining ring  181  received in a radially inwardly extending groove  183 . Additionally, bearing  178  is supported along an inner wall  182  of a mounting member  184 . The bearing can be secured on the mounting member in any suitable manner. For example, in  FIG. 2 , an outer race (not numbered) is captured between a shoulder  186  and a retaining ring  188  received in a radially outwardly extending groove  190 . Mounting member  184  can be secured on a vehicle chassis or body in any suitable manner for retaining the various suspension components in the proper position and transmitting the inputs therefrom to the chassis or body of the vehicle, such as by using mounting studs  192 , for example.  
         [0022]     It is to be distinctly understood that the foregoing embodiment is merely exemplary of one suitable embodiment of the present novel concept, and that a variety of modifications and alterations can be made without departing from the scope and intent of the present novel concept. For example, isolator  144  could alternately be captured on or within end member  106  by crimping, swaging or otherwise deforming a portion of central wall  130  instead of using a threaded connection with insert cap  154 . In which case, either one or both of the jounce and rebound washers could optionally be formed as part of the inner sleeve or otherwise affixed on isolator  144 . As another example, bearing  178  could be captured and/or retained on one or both of end member  106  and mounting member  184  by crimping swaging or otherwise deforming a portion of the end or mounting member instead of using retaining members, such as retaining rings  181  and  188 . Such modifications, and others, could result in a more permanently assembled air spring assembly and may be better suited for mass production practices. It is to be understood that other such production oriented modifications are likewise intended to fall within the scope of the present novel concept.  
         [0023]      FIG. 3  illustrates air spring and damper assembly  100  secured on a vehicle chassis VHC through bearing  178  and mounting member  184 . Additionally, numerous exemplary load paths are superimposed over the air spring and damper assembly, bearing and mounting member to generally indicate exemplary paths through which load inputs, such as air spring, jounce bumper and damper forces, for example, can be directed. An air spring force ASF is applied to end member  106  by the air pressure within the spring chamber of the air spring, as well is understood by those of skill in the art. Force ASF on end member  106  is transmitted to vehicle chassis VHC along a rigid-member load path formed by substantially rigid components. In the embodiment in  FIGS. 1-3 , a rigid-member load path RP 1  includes bearing  178  and mounting member  184  and force ASF is transmitted therealong. Thus, it will be appreciated that end member  106 , bearing  178  and mounting member  184  are all substantially rigid members and that force ASF is not directed to any substantial degree or amount through isolator  144 . It will be understood, however, that in practice, some portion of the air spring load could be directed through the isolator, such as due to the air pressure within the air spring acting on the exposed surface area of the flexible material or jounce washer, for example. By utilizing the present novel concept, however, such undesirable load inputs are minimized and the majority of the air spring load input is directed through a rigid-member load path, such as load path RP 1  discussed above, for example. As a more specific example of a load input distribution, from about 93 percent to about 99 percent of the sprung mass of the vehicle corner can be directed along a rigid-member load path and, preferably, from about 98 percent to about 99 percent of the sprung mass of the vehicle corner is directed along a rigid-member load path.  
         [0024]     As is generally known by those of skill in the art, jounce forces operate in a direction in which a wheel of a vehicle moves toward or into the chassis of the vehicle, and such a jounce direction is indicated by arrow JNC in  FIG. 3 . Oppositely, rebound forces act in a direction of a wheel moving down or outwardly from the chassis of a vehicle, and such a rebound direction is indicated by arrow RBD in  FIG. 3 . Upon the extreme movement of a wheel in the jounce direction, which is indicated by arrow JNC, the piston or other, lower end member of an air spring will impact a jounce bumper, such as bumper  120 , for example, and generate a jounce bumper force JBF that also acts in direction indicated by arrow JNC. As mentioned above, the jounce bumper is in abutting engagement with the upper end member of the air spring, such as top cap  106 , for example, and jounce bumper force JBF is transmitted from the jounce bumper into the end member and through to vehicle chassis VHC along a rigid-member load path. Another exemplary rigid-member load path is shown in  FIG. 3  as load path RP 2 , which includes bearing  178  and mounting member  184 . Rigid-member load path RP 2  is substantially similar to load path RP 1 , but path RP 2  begins from the jounce force on the bumper rather than the air spring input load.  
         [0025]     The action of damper  104  as is well understood by those of skill in the art, and includes a jounce damper force JDF acting in the direction indicated by arrow JNC and a rebound damper force RDF acting in the direction indicated by arrow RBD. Jounce damper force JDF and rebound damper force RDF are respectively transmitted along a compliant-member load path rather than a rigid-member load path discussed above. One exemplary compliant-member load path is shown in  FIG. 3  in association with jounce damper force JDF as load path IP 1 . Jounce damper force JDF is directed along compliant-member load path IP 1 , which includes jounce washer  172 , isolator  144  and end member  106 . Path IP 1  is shown in  FIG. 3  as including insert cap  154 . However, it will be appreciated that in other constructions, isolator  144  may be retained by end member  106  without insert cap  154 , which would therefore be eliminated from load path IP 1 . Thereafter, jounce damper force JDF is directed along path IP 1  which extends through bearing  178  to mounting member  184 . Rebound damper force RDF is transmitted from damping member  118  along a compliant-member load path IP 2 , which includes rebound washer  174 , isolator  144  and end member  106 . Thereafter, rebound damper force RDF is directed along path IP 2  which extends through bearing  178  to mounting member  184 .  
         [0026]     Another exemplary embodiment of an air spring  200  in accordance with the present novel concept is shown in  FIG. 4  and includes a first end member, such as a top cap  202 , for example, a second end member, such as a piston (not shown), for example, and a flexible spring member, such as a flexible wall or sleeve  204 , for example, secured therebetween, such as by using a crimp ring  206 , for example, along each end thereof. A suitable damping member (not shown), such as damper  104 , for example, will be used in operative association with air spring  200  in a manner substantially similar to that discussed hereinbefore with regard to air spring  102  in  FIGS. 1-3 . Top cap  202  includes an outer radial wall  208  secured to a central wall  210  by an annular web portion  212 . The annular web portion includes a bottom surface  214  and a jounce bumper  216  disposed adjacent bottom surface  214 . The jounce bumper includes an inside wall  218  forming a passage  220  therethrough. Additionally, jounce bumper  216  includes a recess  222  that extends inwardly from an end wall  224 , which is disposed in abutting engagement with bottom surface  214  when undergoing a jounce bumper load.  
         [0027]     Central wall  210  includes an inside surface  226  and an outer surface  228 . Inside surface  226  forms a passage (not numbered) extending through top cap  202  and an isolator  230  is disposed within the passage along inside surface  226 . Isolator  230  includes an inner sleeve  232  and elastomeric material  234  extending between inner sleeve  232  and inside surface  226  of central wall  210 . Isolator  230  differs from isolator  144  discussed hereinbefore in that an outer sleeve, such as outer sleeve  148  of isolator  144 , for example, is not used. Rather, elastomeric material  234  is directly molded onto or otherwise adhered along inside surface  226 . A bearing  236  can be secured along outside surface  228  in any suitable manner, such as by using a retaining ring  238 , for example, as has been discussed above. Bearing  236  is supported along an inside wall  240  of a mounting member  242  and can be secured therealong in any suitable manner, such as by using a retaining ring  244 , for example, as has been discussed above.  
         [0028]     Still another exemplary embodiment of an air spring  300  in accordance with the present novel concept is shown in  FIG. 5  and includes a first end member, such as a top cap  302 , for example, a second end member, such as a piston (not shown), for example, spaced from the first end member and a flexible spring member, such as a sleeve  304 , for example, secured therebetween in a suitable manner, such as by using a crimp ring  306 , for example, along each end thereof. Top cap  302  is similar to top caps  106  and  202  discussed hereinbefore, and includes an outer radial wall  308 , a central wall  310  and an annular web portion  312  extending therebetween. The annular web portion includes a bottom surface  314  suitable for engaging an end wall  316  of a jounce bumper  318 . The jounce bumper also includes a recess  320  formed inwardly from end wall  316  and an inside wall  322  forming a passage  324  therethrough.  
         [0029]     A suitable damping member (not shown) includes a damping rod  326  as is well known by those of skill in the art. Damping rod  326  includes a threaded end  328  and an annular shoulder  330 . A plurality of radially inwardly extending grooves  332  can optionally be provided and may be suitable for receiving a sealing member, such as an o-ring (not shown), for example.  
         [0030]     Central wall  310  includes an outer surface  334  and an inner surface  336 . A shoulder  338  is formed along inner surface  336  and a radially outwardly extending groove  340  is spaced therefrom. One or more additional grooves  342  can optionally be provided and can optionally receive a sealing member, such as an o-ring  344 , for example.  
         [0031]     An isolator  346  is disposed within a passage  348  formed through end member  302  by inner surface  336 . Isolator  346  includes an inner sleeve  350 , an outer sleeve  352  and elastomeric material  354  extending therebetween. Outer sleeve  352  is captured between shoulder  338  and a retaining ring  356  received within groove  340 . Damping rod  326  extends through a passage (not shown) formed through isolator  346  by inner sleeve  350 . The inner sleeve is captured on damping rod  326  between a jounce washer  348  and a rebound washer (not shown) and threaded nut (not shown) spaced opposite the jounce washer, as discussed above. A bearing  360  is supported along outer surface  334  of central wall  310  and engages a mounting member  362  and is secured therebetween in a suitable manner, such as those discussed in detail above.  
         [0032]     It will be appreciated that air springs  200  and  300  discussed above function to transmit loads to a vehicle chassis or body along rigid-member and isolating load paths, such as those discussed above with regard to assembly  100  in  FIGS. 1-3 , for example. Additionally, it will be understood that load paths other than or in addition to paths RP 1 , RP 2 , IP 1  and IP 2  can be used without departing from the principles of the present novel concept.  
         [0033]     While the invention has been described with reference to the foregoing embodiments and considerable emphasis has been placed herein on the structures and structural interrelationships between the component parts of the embodiments disclosed, it will be appreciated that other embodiments of the present novel concept can be made and that many changes can be made in the embodiments illustrated and described without departing from the principles of the present novel concept. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present novel concept and not as a limitation. As such, it is intended that the present novel concept be construed as including all such modifications and alterations insofar as the same come within the scope of the appended claims and the equivalents thereof.