Abstract:
A corner assembly includes a suspension module and a wheel assembly. In order to compensate for tolerance stack up in relation to a specified height of the corner assembly, the attachment between a damper of the suspension module and a knuckle of the wheel assembly is adjusted. The amount of adjustment is determined by measuring the assembled length of the suspension module, comparing the measured length to a standard length and determining an amount of adjustment necessary.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/890,637, filed on Feb. 20, 2007. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to setting a specified vehicle height for a vehicle. More particularly, the present disclosure relates to a positioning feature and a positioning method to be utilized in vehicle suspension systems for achieving precise vehicle height tolerances. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    The accurate setting of the suspension system of a vehicle at the design position for the vehicle height improves passenger comfort, vehicle handling performance and the visual aspects of the vehicle. The design position for the vehicle height is directly related to the design length of the McPherson suspension module or the pseudo McPherson suspension module mounted on the vehicle. Typical vehicle height tolerances can vary from about ±7 mm to about ±10 mm. If the vehicle manufacturer wants to reduce these tolerances, significant extra efforts are required and special manufacturing techniques need to be developed resulting in significant additional costs. 
         [0005]    Vehicle manufacturers establish what the design height or vehicle height of the vehicle and thus the McPherson suspension module should be. Typically, a vehicle manufacturer will determine a specific weight of the vehicle at which the design height is defined. The specific weight can include the driver, a passenger and a specified weight for baggage of the driver and the passenger. At this specific weight of the vehicle, the nominal vehicle height and the allowed tolerances are defined. 
         [0006]    A typical McPherson suspension module comprises a top mount connecting the module to the car body, a bearing for allowing rotation of the wheel, a spring supporting the vehicle&#39;s weight, a strut or damper providing vehicle damping, an upper and a lower spring seat supporting the spring and an anti-roll bracket to connect the anti-roll link to the strut or damper. 
         [0007]    The achieved McPherson suspension module tolerance will be a combination of the tolerances of the top mount, the bearing, the spring, the upper seat position, the lower seat position on the strut and the positioning tolerances (in height) of the strut or damper into the knuckle. Typical design methods that ensure a correct positioning of the strut or damper into the knuckle include a reduced diameter for the strut or bearing that is inserted into the knuckle, a local area of the strut or damper tube is increased to act as a stop for the knuckle, a hook-shaped bracket can be welded to the strut or damper tube which acts as a stop for the bolt extending through the knuckle, or a T-shaped bracket can be welded to the strut or damper tube which acts as a stop in both a vertical and an angular position. The utilization of one of these methods also adds the tolerances of these components to the cumulative tolerances of the vehicle height. 
         [0008]    In order to minimize the height tolerances of the assembled McPherson suspension module, you can individually reduce the tolerances for each of the components discussed above. This typically only results in a minimal reduction of the overall tolerance band and can lead to significantly higher manufacturing costs. 
       SUMMARY 
       [0009]    The present disclosure provides a manufacturing and measuring method to measure the nominal length deviation of the assembled McPherson suspension module. After measuring the nominal length deviation of the assembled McPherson suspension module, an adjustment shim can be selected which, when used during the assembly of the McPherson suspension module to the knuckle, positions the knuckle in relation to the McPherson suspension module such that the vehicle height tolerances are minimized. 
         [0010]    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 
         [0011]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0012]      FIG. 1  is a side view of a McPherson suspension module in accordance with the present disclosure assembled into a vehicle; 
           [0013]      FIG. 2  is a side view of the strut or damper illustrated in  FIG. 1  with a positioning fixture mounted on the outer tube; 
           [0014]      FIG. 3  is a side view of a strut or damper similar to  FIG. 2  but with a positioning fixture in accordance with another embodiment of the present disclosure mounted on the outer tube; 
           [0015]      FIG. 4  is a side view of a strut or damper similar to  FIG. 2  but with a positioning fixture in accordance with another embodiment of the present disclosure mounted on the outer tube; 
           [0016]      FIGS. 5A-5C  illustrate various designs for the fixture or shim illustrated in  FIG. 6 . 
           [0017]      FIG. 6  is a plan view of the fixture of shim illustrated in  FIG. 5A ; 
           [0018]      FIG. 7  is a graph illustrating the measuring method and adjustment method in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0020]    Referring now to  FIG. 1 , a corner assembly  10  of a vehicle which incorporates the manufacturing and method in accordance with the present disclosure is illustrated. Corner assembly  10  comprises a McPherson suspension module  12 , a body plate  14 , and a wheel assembly including a knuckle  16  and a wheel  18 . 
         [0021]    McPherson suspension module  12  comprises an upper mount assembly including a top mount assembly  30 ; a bearing  32 ; a spring  34 ; a strut or damper  36 ; an upper spring mount  38 ; a lower spring mount  40 ; a dirt shield  42 ; a compression bumper  44 ; an anti-roll bar bracket  46 ; an ABS bracket  48  and a brake hose bracket  50 . 
         [0022]    Top mount assembly  30  is secured to body plate  14  using a plurality of threaded studs and their associated nuts or retainers. Top mount assembly  30  includes a metal top mount and an elastomeric bushing typically bonded to the metal top mount. Bearing  32  is disposed between top mount assembly  30  and upper spring mount  38  to allow for the rotation of wheel  18 . Spring  34  extends between upper spring mount  38  and lower spring mount  40  which is attached to strut or damper  36  to support the body or sprung weight of the vehicle. Strut or damper  36  extends through the center of lower spring mount  40 , spring  34 , upper spring mount  38 , bearing  32  and top mount assembly  30 . Strut or damper  36  is secured to knuckle  16  as discussed below and to top mount assembly using a rebound plate  64  and a nut  66  to limit the extended position of wheel  18 . Strut or damper  36  provides for damping of the motion of the body or sprung weight of the vehicle as it moves in relation to the suspension or unsprung weight of the vehicle. Strut or damper  36  includes piston rod  68  which receives rebound plate  64  and nut  66 , a piston assembly (not shown) and an outer tube  70  within which the piston assembly slides. Damping forces are generated by controlling fluid flow from one side of the piston assembly to the opposite side of the piston assembly as is known in the art. Strut or damper  36  can be a mono-tube design, a dual-tube design or any other design of damper known in the art. Dirt shield  42  is positioned between upper spring mount  38  and lower spring mount  40  in the center of spring  34  to protect piston rod  68  from water, sand, small stones and other contaminants. Compression bumper  44  is disposed within dirt shield  42  and around piston rod  68  to limit the compressed position of wheel  18 . 
         [0023]    As discussed above, lower spring mount  40  is attached to strut or damper  36  by being welded or otherwise secured to outer tube  70  of strut or damper  36 . Other components welded or otherwise secured to outer tube  70  of strut or damper  36  include anti-roll bar bracket  46  which is used to connect the anti-roll bar link to strut or damper  36 . ABS bracket  48  which is used to fix the ABS cable to strut or damper  36 , and brake hose bracket  50  which connects the vehicle&#39;s brake hose to strut or damper  36 . 
         [0024]    Referring now to  FIG. 2 , outer tube  70  of strut or damper  36  and its assembly to knuckle  16  is illustrated in greater detail. Outer tube  70  is a notched tube which includes a local diameter increased area  72 . An annular seat  74 , preferably of metal, is welded or otherwise attached to outer tube  70  abutting local diameter increased area  72 . A fixture or shim  76 , preferably of plastic is disposed between seat  74  and knuckle  16  to compensate for the accumulated tolerances of McPherson suspension module  12  and thus more accurately position the body or sprung weight at the specified design height as detailed below. 
         [0025]      FIG. 3  illustrates seat  74  positioned using an outer tube  70 ′ which can replace outer tube  70 . Outer tube  70 ′ includes a large diameter section  80 ′ and a reduced diameter section  82  which is sized to fit into knuckle  16 . Seat  74  is attached to outer tube  70 ′ by welding or otherwise attaching seat  74  to outer tube  70 ′ with seat  74  abutting the transition region between section  80  and section  82 . 
         [0026]      FIG. 4  illustrates seat  74  positioned using an outer tube  70 ″ which can replace outer tube  70  also. Outer tube  70 ″ is a straight tube onto which seat  74  is welded or otherwise attached at the proper position. 
         [0027]    Fixture or shim  76  can have different shapes and can be made of different materials. The preferred material is a plastic material such as Polypropelene (PP) or Polyamide (PA). The shape of fixture or shim  76  must be such that it is easily attached to seat  74  at the end of the manufacturing process but cannot detach from seat  74  at the end of the manufacturing process but cannot detach from seat  74  during transport or handling. Fixture or shim  76  when mounted to seat  74  must automatically be at the correct position (no possibility to mount at a wrong position) and as mentioned above, must remain fixed during transportation. 
         [0028]    Referring now to  FIGS. 5A-5C  and  FIG. 6 , different designs for fixture or shim  76  are illustrated.  FIG. 5A  illustrates fixture or shim  76  which defines a generally rectangular slot  90  into which seat  74  is positioned.  FIG. 5B  illustrates a fixture or shim  76 ′ which includes a contoured slot  90 ′ into which an annular seat  74 ′, having a contour matching the contour of slot  90 ′, is positioned.  FIG. 5C  illustrates a fixture or shim  76 ″ which includes a contoured inner diameter  92  which mates with an annular contoured region  94  located on outer tube  70 .  FIG. 6  illustrates a top view of fixture or shim  76 . Fixture or shim  76  has a generally U-shape such that fixture or shim  76  can be assembled over seat  74  when seat  74  is assembled to outer tube  70 . Fixtures or shims  76 ′ and  76 ″ are also generally U-shaped similar to fixture or shim  76 . 
         [0029]    Referring now to  FIG. 7 , the method of compensating for the tolerance build up for the vehicle height is illustrated. Initially, seat  74  or  74 ′ or contoured region  94  will serve as a reference plane to measure the height of McPherson suspension module  12  between top mount assembly  30  and strut or damper  36 . Depending on the length deviation measured, fixture or shim  76 ,  76 ′ or  76 ″ having a specific height h (shown in  FIG. 2 ) will be clipped or assembled onto seat  74  or  74 ′ to compensate for the measured deviation from the specified length dimension. Depending on the tolerances achieved without compensation and the desired tolerance band, a plurality of fixtures or shims  76 ,  76 ′ or  76 ″ having different heights h can be provided. 
         [0030]    As illustrated in  FIG. 7 , a tolerance band of ±7 mm is achieved without any compensation measures. The desired tolerance band is assumed to be ±3.5 mm. If we assume no measurement error and no tolerance on the height h of fixture or shim  76 ,  76 ′ or  76 ″ and its assembly, then one fixture having a height h equal to  7 mm is sufficient to achieve the requested tolerance band of ±3.5 mm. First, the mean length is shifted from 0 to −3.5 mm. This yields a tolerance band of −10.5 mm to +3.5 mm. If the initial deviation is measured to be between −3.5 mm and +3.5 mm, nothing is added since the length is already within the required tolerance band. If during the manufacturing process for McPherson suspension module  12 , the module length deviation of McPherson suspension module  12  is measured between −10.5 mm and −3.5 mm, the 7 mm fixture or shim  76 ,  76 ′ or  76 ″ is added. This results in a deviation between −3.5 mm and +3.5 mm which is within the required tolerance band. 
         [0031]    This illustrates how the present disclosure works. There are some practical considerations that must be taken into account which will mostly increase the number and sizes of fixtures or shims  76 ,  76 ′ or  76 ″. For example, a measurement error, of ±1 mm will reduce the available tolerance band from ±3.5 mm to ±2.5 mm. Similar consideration should be given to the tolerance of the height h of fixtures or shims  76 ,  76 ′ or  76 ″. 
         [0032]    While the above embodiments have been illustrated using fixture or shims  76 ,  76 ′ or  76 ″, it is also possible to achieve the desired position accuracy without the use of fixtures or shims  76 ,  76 ′ or  76 ″. This can be accomplished by identifying the required correction during the manufacturing of the McPherson suspension module and utilize an indicator such as specific color codes to indicate the correction needed and attach this indicator to the McPherson suspension module. During the mounting of the McPherson suspension module to the knuckle, the operator could then use a positioning tool having a thickness identical to the correction to establish the correct positioning of the McPherson suspension module to the knuckle. After tightening of the knuckle clamping bolt, the positioning tool can be removed and reused.