Patent Publication Number: US-2018031043-A1

Title: Center bearing assembly with shear member

Description:
TECHNICAL FIELD 
     The present disclosure relates to a center-bearing assembly having a shear member configured to release the bearing from the assembly in response to a sufficient impact to the driveshaft. 
     BACKGROUND 
     Motor vehicles typically include an engine for propelling the vehicle. The engine is connected to a transmission that modifies the engine output to a desired speed ratio. A driveshaft (also known as a propshaft) is driveably connected between an output of the transmission and a differential to transmit torque to the driven wheels. The driveshaft is secured to a chassis of the vehicle by a bracket assembly. The bracket assembly includes a bearing having an inner race fixed to the driveshaft and an outer race fixed to the bracket. 
     SUMMARY 
     According to one embodiment, a center-bearing assembly includes an annular housing having a circumferential wall with a lip extending radially inward and includes a flange outboard of the circumferential wall. A roller bearing is sized to encircle a vehicle driveshaft and is disposed within the housing between the lip and the flange. An annular retainer is connected to the flange and includes an annular notch configured to shear in response to impact to the driveshaft allowing the bearing to release from the housing. 
     According to another embodiment, a center-bearing assembly for a driveshaft of a vehicle includes an annular housing supported within a bracket assembly connected to a frame of the vehicle. The housing has a circumferential wall with a lip extending radially inward from a first end and has a flange with a portion extending radially outward from a second end. A roller bearing is concentric with the housing and has an outer race disposed within the housing such that the bearing is located between the lip and the flange and such that a first side of the bearing is disposed against the lip. The bearing further has an inner race fixed to the driveshaft. A shear ring is connected to the flange and includes a designed fracture portion defining a breakaway tab disposed against a second side of the bearing. The fracture portion is configured to, in response to an impact having a magnitude exceeding a shear strength of the fracture portion, shear at the fracture portion causing the breakaway tab to separate allowing the bearing to slide out of the housing. 
     According to yet another embodiment, a driveshaft assembly includes a driveshaft, and a bearing having an inner race fixed to the driveshaft, an outer race, and bearing elements disposed between the races. A bearing support is mountable to a vehicle. A bearing can is mounted in the support and defines an opening that receives the bearing therein. A shear ring is connected to the can, engages the bearing, and including an annular notch configured to shear and release the bearing from the can. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an example vehicle having a driveshaft assembly. 
         FIG. 2  is a front view of an annular shear ring of a center-bearing assembly. 
         FIG. 3  is side view, in cross section, of a center-bearing assembly. 
         FIG. 4  is a magnified side view of the center-bearing assembly of  FIG. 3 . 
         FIG. 5  is a perspective view of the annular shear ring of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Referring to  FIG. 1 , a vehicle  20  (such as a front engine, rear-wheel drive vehicle or a four-wheel drive vehicle) may include an engine  22  and a transmission  24 . The transmission  24  includes an output shaft  25  that is coupled to a front end of a driveshaft  26 . The rear end of the driveshaft  26  is coupled to the rear differential  28  or similar device. The driveshaft  26  may be coupled via universal joints (U-joints), constant-velocity joints (CV Joints), or the like. The driveshaft  26  transmits power from the transmission  24  to a final drive disposed within the rear differential  28 . The final drive is driveably connected to the rear wheels  32  via one or more rear axles  30 . If the vehicle is four-wheel drive, the front end of the driveshaft  26  is coupled to the transfer case. The driveshaft  26  may include a center-bearing assembly  34  that support the driveshaft to the vehicle chassis. This will be explained in more detail below. 
     In one embodiment, the driveshaft  26  is a multi-segment driveshaft that includes a front shaft  36  and a rear shaft  38 . The front shaft includes a yoke  40  that couples to a yoke  47  of the transmission output shaft  25  at a forward U-joint  48 . The yoke  40  includes a flange that is connected to a tube  42  via welding or other means known in the art. The tube  42  extends rearwardly from the yoke  40  and terminates at a flange of a yolk shaft  44 . The shaft  44  extends rearwardly and terminates at a rear yoke  46 . The rear yoke  46  is coupled to a front yoke  50  of the rear shaft  38  at an intermediate U-joint  52 . The front yoke  50  is connected to a tube  54  that extends rearwardly to a rear yoke  56 . The rear yoke  56  couples to a yoke  58  of the differential input shaft  60  at a rear U-joint  62 . 
     Due to their length, driveshafts typically require at least one support structure to suspend the driveshaft beneath an underside of the vehicle  20 . The driveshaft  26  includes a center-bearing assembly  34  that mounts the driveshaft  26  to a chassis  66  of the vehicle  20 . For example, the assembly  34  includes a bracket that bolts to a cross member  70  that extends between the frame rails  72 . 
       FIGS. 2 through 5  illustrate different views of a center-bearing assembly according to one embodiment. Referring to these figures, the center-bearing assembly  34  may include a bracket  68  for connecting the assembly  34  to the vehicle chassis  66 . A bushing (or resilient member)  90  is disposed within the bracket  68 . The bushing  90  defines a bearing receiving portion  92  that receives the bearing therein. The bushing may be formed of an elastomeric material such as rubber. The bushing absorbs vibrations from the driveshaft to prevent them from traveling to the chassis. 
     The bearing assembly  34  also includes an annular housing (can)  94  that is generally in the shape of a tube. The can  94  may include a circumferential wall  96  having an outer surface  98 , an inner surface  100 , a first end  102 , and a second end  104 . The can  94  is received within the bushing  90  such that the outer surface  98  is disposed against an inner surface of the bushing. The can  94  may also include a lip  106  extending radially inward from the first end  102 . The lip  106  includes a bearing-engaging surface  108  and an inboard wall  110  that defines a circular hole  112 . A flange  114  of the annular housing  94  generally extends radially outward from the second end  104 . The flange  114  may include a retainer-engaging tab  116  that is substantially concentric with the circumferential wall  96 . The diameter of the tab  116  is larger than the diameter of the circumferential wall  96 . The tab  116  is connected to the circumferential wall  96  by a radially extending wall  118 . The wall  118  includes a retainer-facing surface  119  that is coplanar with an end surface  121  of the bearing  120 . 
     A roller bearing  120  is secured within the annular housing  94 . The roller bearing  120  may be any type of roller bearing including a ball bearing, a needle bearing, or other type. The roller bearing  120  supports the driveshaft  26  for rotation within the assembly  34 . The bearing  120  may include an inner race  122  having an inner surface  124  and an outer surface  126 . The inner surface  124  defines a circular hole  125  that receives the driveshaft  26  therein such that the inner surface  124  engages the outer surface of the driveshaft. In the embodiment illustrated in  FIG. 1 , the inner race is disposed on the yolk shaft  44 . Is to be understood, however, that the center bearing assembly  34  may be disposed on a different portion of the driveshaft. 
     The bearing  120  also includes an outer race  128  that is concentric with, and circumscribes, the inner race  122 . The outer race  128  has an inner surface  130 , an outer surface  132 , a first end surface  134 , and a second and surface  136 . The end surfaces extend between the inner and outer surfaces. A plurality of roller elements  140 , such as metal balls or cylinders, are disposed between the inner and outer races  122 ,  128 . The roller elements  140  rollably engage between the races allowing for low-friction, relative movement between the races. The roller elements  140  may be retained in a cage  142 . Grease may be disposed within the cavity between the races and seals (not shown) are provided to retain the grease and prevent contaminants from entering into the cavity. 
     The bearing  120  is disposed within the annular housing  94  such that the outer surface  132  of the outer race  128  is disposed against (or near) the inner surface  100  of the circumferential wall  96  and the first end surface  134  is disposed against the bearing-engaging surface  108  of the lip  106 . The annular housing  94  may include a friction surface  144  disposed on the inner surface  100  and sandwiched between the circumferential wall  96  and the outer race  128 . The friction surface  144  increases the friction coefficient between the roller bearing  120  and the annular housing  94  to resist the bearing from sliding relative to the housing  94 . The friction surface may be made of an elastomeric material such as rubber. The friction surface may be omitted in some embodiments. 
     The lip  106  prevents the roller bearing  120  from sliding axially to the left, however, additional retaining means is required to prevent axial movement of the bearing  120  to the right. As such, the bearing assembly  34  includes an annular retainer  146 . The retainer  146  may be a shear ring having a cylindrical portion  148  and a retaining portion  150  that extends radially inward from the cylindrical portion. The cylindrical portion  148  may include a circumferential wall  152  having an outboard surface  154  and, an inboard surface  156 . A circular hole  158  is defined by the inboard surface  156 . The retaining portion  150  may include a front face  160 , a back face  162 , and an inboard surface  164  that defines a circular hole  166 . The retainer  146  is disposed in the flange portion  114  of the annular housing  94 . In one embodiment, the outboard surface  154  of the circumferential wall  152  is press fit to the retainer-engaging tab  116  of the flange. The front face  160  of the retaining portion  150  is disposed against the second end surface  136  of the outer race  128  to retain the roller bearing  120  within the annular housing  94 . 
     During an impact, one or more vehicle structures cooperate to absorb energy in order to reduce impact forces on the occupants of the vehicle. The driveshaft may be utilized to absorb some of these forces. During a frontal impact, forces travel through the bumper, into the engine, and subsequently into the driveshaft. In order to absorb this energy, the driveshaft may be designed to deform (i.e., crush) or displace rearwardly. The center-bearing assembly not only provides vertical support but also provides fore-and-aft support. In order for the driveshaft to displaced rearwardly in response to an impact force, the bearing assembly must either detach form the frame, or have one or more bearing components separate from the bracket or bushing. Designs relying on bracket failure are difficult to tune and the assembly process injects uncertainty into the shear strength. As such, it may be preferable for the bearing to separate from the bushing or from itself 
     In the illustrated embodiment, the center-bearing assembly  34  is designed such that the roller bearing  120  separates from the annular housing  94  in response to an impact of sufficient magnitude. The annular housing  94  is disposed on the vehicle such that the lip  106  faces forwardly and the flange  114  faces rearwardly. Thus, the shear ring  146  and the friction surface  144  (if included) are the only components that resist reward movement of the driveshaft  26  relative to the annular housing. The shear ring  146  may include a fracture portion (or weakened portion) having a reduced cross-sectional area, and thus a reduced shear strength. In one embodiment, the reduced cross-sectional area is created by providing a notch  170  into the front face  160 . In other embodiments, the fracture portion may be formed by apertures. 
     The notch  170  may be V-shaped and include first and second angular walls  172 ,  174  intersecting at a valley  176 . The notch  170  may be circular and extend around the entire shear ring  146 . A breakaway tab  168  of the retaining portion  150  is defined between the inboard surface  164  and the valley  176 . The notch  170  may be located on the front face  160  such that the valley  176  is radially aligned (or nearly aligned) with the interface between the outer race  128  and the annular housing  94 . This placement of the notch disposes only the breakaway tab  168  against the roller bearing  120 . In response to a shear force of sufficient magnitude, the breakaway tab  168  separates from the main body of the shear ring  146  allowing the roller bearing  120  to slide out of the annular housing  94  if the friction force of the friction surface  144  is overcome. 
     The shear strength of the retainer  146  at the notch  170  may be less than the shear strength of the press fit to ensure that the bearing assembly  34  fails at the notch  170 . For example, the shear strength of the retainer  146  at the notch  170  may be between 20 to 80 kilonewtons (kN). In order to achieve this shear strength, the depth of the notch may be between 10 to 50 percent of the thickness of the retaining portion  150 . 
     While example embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.