Patent Application
20050253351
The subject invention generally relates to a suspension bracket assembly for a vehicle axle housing that is preloaded during attachment to control transfer of the load path from an input to the suspension.
Medium and heavy duty vehicles include suspensions that are attached to axle housings in various different manners. Traditionally, these suspensions include loose piece brackets that are welded to the axle housing, or are clamped to the axle housing to define a suspension mount interface. A conventional loose piece suspension mount interface includes an upper bracket positioned between an upper surface of the axle housing and a suspension main support member and a lower bracket positioned underneath the axle housing. A pair of U-bolts extends over the suspension main support member and are fastened against the lower bracket underneath the axle housing.
This suspension mount interface creates many design challenges. There are a variety of suspension types and each type of suspension can have many different configurations. This means that a variety of attachment hardware, i.e. brackets, clamps, fasteners, etc., are needed to accommodate all of the suspension mount interface variations. This proliferates components and increases cost.
Additionally, the fatigue life of the axle housing can be affected. During vehicle operation, the upper and lower brackets can rub against the axle housing. This can generate cracks in the housing, which can lead to premature wear or component failure. Also, any movement of the brackets relative to the axle housing, which may be caused by loosening of the fastener attachment, can move the suspension mount interface out of the original installation position, which can cause loading through the axle housing in undesirable locations. This can also cause premature wear or failure.
There is a need for a suspension mount interface for a vehicle axle that can accommodate many different suspension types while reducing costs by deproliferation. The suspension mount should be easily incorporated into existing axle housing configurations and should improve axle housing fatigue life in addition to overcoming the other above-mentioned deficiencies in the prior art.
A suspension mount interface for an axle assembly utilizes a two-piece suspension bracket assembly that is pre-assembled and then installed over an axle housing. Once installed over the housing, the bracket pieces are subjected to a preload force as the pieces are attached together. The suspension bracket assembly exerts this clamping or preload force against the axle housing during the attachment process. This preload force ensures that positive contact between the suspension bracket assembly and the axle housing occurs only at predefined locations, which controls the suspension load input path regardless of the type of suspension being used or the attachment interface between the suspension and the axle housing.
In one disclosed embodiment, the suspension bracket assembly includes a first bracket member and a second bracket member. The bracket members are held fixed relative to each other and then are slid over one end of the axle housing to substantially surround the axle housing. The bracket members can be held fixed relative to each other by being clamped together in a fixture, hinged together, or fastened together prior to being installed over the axle housing. Once in position, the first and second bracket members are attached to each other. This attachment can be a welded or bolted joint. During attachment, the preload force is applied to the first and second bracket members, which exert the clamping or preload force against the housing to control the suspension load path.
The first and second bracket members are geometrically configured to ensure positive contact for the clamping force only along predetermined contact areas of the axle housing. In one disclosed embodiment, the axle housing includes a polygonal cross-section that includes a plurality of angled surfaces. The bracket members are configured such that positive contact is only exerted against the angled surfaces. Preferably, these angled surfaces are positioned at corner locations on the axle housing.
The subject suspension bracket assembly provides an improved suspension mount interface that is easily incorporated into existing axle housings and which can be used with a variety of suspensions. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
An axle assembly is shown generally at 10 in
A suspension mount interface, shown generally at 26, is used to mount the axle assembly 10 to a vehicle suspension 28. The suspension 28 is supported by a vehicle frame 30. The suspension mount interface 26 includes a first bracket assembly 32 positioned at the first leg portion 22 and a second bracket assembly 34 positioned at the second leg portion 24. The bracket assemblies 32, 34 connect the axle assembly 10 to the suspension 28. While the bracket assemblies 22, 24 are shown as being used to interconnect a drive axle 10 and a suspension 28, it should be understood that the subject bracket assemblies 22, 24 could also be beneficially used in other axle configurations, such as non-drive, steer, trailer, or tag axles, for example.
The bracket assemblies 32, 34 are comprised of a two-piece configuration that is pre-assembled prior to attachment to the axle housing 18. The pre-assembled bracket pieces are held fixed relative to one another and may or may not be attached to each other. One bracket assembly is then slid over each of the first 22 and second 24 leg portions such that the bracket assemblies 32, 34 substantially surround the leg portions 22, 24. The bracket assemblies 32, 34 are then secured or attached together after being installed over the leg portions 22, 24. During the attachment process, the bracket pieces are subjected to a preload, which generates a squeezing or clamping force around the axle housing 18. This causes the bracket pieces to contact the axle housing 18 only along predetermined contact areas. This configuration helps isolate the axle housing 18 from the direct load path for suspension input loads.
One example of a bracket assembly 36, which is installed over the first 22 and second 24 leg portions of the axle housing 18, is shown in
The vertical side walls 42 and upper 38 and lower 40 horizontal surfaces are generally flat, and are orientated at generally ninety degrees relative to one another. In other words, the vertical side walls 42 are orientated generally perpendicular to the upper 38 and lower 40 horizontal walls. The angled surfaces 44 are non-parallel to the vertical side walls 42 and the upper 38 and lower 40 horizontal walls and thus intersect planes defined by the vertical side walls 42 and the upper 38 and lower 40 horizontal walls at an angle. While an octagonal cross-section is shown, it should be understood that the subject invention could be beneficial to other multi-sided axle housing cross-sections.
The bracket assembly 36 includes a first bracket member 46 and a second bracket member 48 that are welded together along a weld interface 50. In the configuration shown in
In this configuration, the upper 46 and lower 48 brackets are held fixed together in a fixture or other similar tooling mechanism (not shown) prior to being slid over the leg portions 22, 24 of the axle housing 18. Once the bracket assembly 36 is installed over the axle housing 18, the pre-load force is applied as the brackets 46, 48 are welded together along the weld interface 50. This preload force ensures that contact between the bracket assembly 36 and the axle housing 18 only occurs along the pad portions. The weld interface location for this configuration is preferred as the weld interface 50 between the upper 46 and lower 48 brackets is isolated from contact with the axle housing 18.
The upper 46 and lower 48 brackets include a plurality of reduced cross-sectional areas 58 that allow the brackets 46, 48 to bend during the welding process. The reduced cross-sectional areas form grooves or channels that extend in a direction parallel to the lateral axis 20. The grooves form hinge points that help the brackets 46, 48 conform to the desired orientation. In other words, the hinge points allow the brackets 46, 48 to bend ensuring that positive contact between the axle housing 18 and the brackets 46, 48 occurs only at the pad portions. This also ensures that gaps 60 are maintained between the upper bracket 46 and the vertical side walls 42.
In this configuration, the only contact between the upper 46 and lower 48 brackets occurs through a horizontal interface. There is no contact between the brackets 46, 48 where vertical loading can be transferred from the lower bracket 46 to the upper 48 bracket. This ensures that any vertical loading goes through the housing 18 at the desired angled surfaces 44.
The upper bracket 46 includes a base portion 62 and a pair of legs 64 extending downwardly from the base portion 62 to distal ends 66. The distal ends 66 each include a boss portion 68 that receives a U-bolt connection 70. One of the legs 64 includes a transversely extending arm 72 that is connected to a shock absorber (not shown). The U-bolt connection 70 is configured such that one U-bolt 70 is positioned on one vertical side of the axle housing 18 and a second U-bolt 70 is positioned on an opposite vertical side of the axle housing 18. A spring member 74 is positioned above the base portion 62 of the upper bracket 46 and below a suspension main support member 76. The U-bolts 70 extend over the main support member 76 and are fastened into the boss portions 68 with a plurality of nuts 78. Additional support members 80 can be positioned between the main support member 76 and the U-bolts 70 as needed.
One main difference with this configuration is that the U-bolt connection is eliminated. Instead, a plurality of studs 88 is used to connect the lower bracket 84 to the suspension main support member 76. An attachment member 90 is positioned on top of the main support member 76. The studs are inserted through openings in the support member 90 and extend into the bosses 68 of the leg portions 64 of the lower bracket 84. The studs 88 are fastened to the support member 90 with a plurality of nuts 92. In this configuration, the transversely extending arm 72 extends from the base portion 62 of the lower bracket 84 as opposed to extending from the distal end 66 of one of the legs 64.
The upper 102 and lower 108 brackets are held fixed together in a fixture or other similar tooling mechanism (not shown) prior to being slid over the leg portions 22, 24 of the axle housing 18. Once the bracket assembly 100 is installed over the axle housing 18, the pre-load force is applied as the brackets 102, 108 are welded together along a weld interface 118. The weld interface 118 is formed between the distal ends 114 of the upper bracket 102 and the distal ends 116 of the lower bracket 108.
The upper 102 and lower 108 brackets each include pad portions 120, similar to those described above with regard to
In this configuration, the suspension 28 is positioned underneath the axle housing 18. The suspension 28 includes a main support member 122 that is positioned below the lower bracket 108. The upper bracket 102 includes a pair of bosses 124 formed at the distal ends 114. The bosses 124 include channels 126 that receive base portions 128 for a U-bolt 130. The U-bolts 130 extend downwardly toward the main support member 122 and are fastened into an attachment member 132, supported underneath the main support member 122, with a plurality of nuts 134.
It should be understood that while the bracket assembly 100 embodiment of
The fore bracket 142 includes a base portion 150 that extends along one vertical side wall 42 and a pair of leg portions 152 that extend along portions of the upper 38 and lower 40 horizontal walls of the axle housing 18. The aft bracket 144 includes a base portion 154 that extends along the opposite vertical side wall 44 and a pair of leg portions 156 that extend along portions of the upper 38 and lower 40 horizontal walls of the axle housing 18. One leg 152, 156 from each bracket 142, 144 is hinged or fastened together at the lower horizontal wall 40 and the other leg 152, 156 from each bracket 142, 144 is fastened together to generate the preload.
The fore 142 and aft 144 brackets each include pad portions 158, similar to those described above with regard to
The subject invention utilizes a two-piece bracket assembly to attach a suspension to an axle assembly. A common two-piece bracket assembly can be used with many different types of vehicle suspension. Thus, the overall number of bracket components can be significantly reduced. This also simplifies integration and installation procedures for different suspension types. Further, the application of the preload during the attachment of the bracket pieces controls and directs the suspension load path to predetermined areas on the axle housing.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
