Patent Publication Number: US-2020282790-A1

Title: High-torsion air strut

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an air spring assembly which is more tolerant of torsion induced by vehicle kinematics. 
     BACKGROUND OF THE INVENTION 
     Suspension systems for automotive vehicles provide vehicle passengers with a more comfortable ride. Air suspension systems utilize air springs, rather than traditional coil springs. Air suspension systems provide different suspension qualities that may be preferable in some vehicles to traditional coil spring suspensions. 
     A conventional aft spring is a device that is arranged between a vehicle body and chassis. The typical air spring has at least one working space, or cavity that is filled with compressed air. Air spring pistons typically seal the aft chamber against a hydraulic shock absorber (damper). Vehicle kinematics may induce torsion into the air spring assembly during the operation of the vehicle. Many air spring systems are limited by the amount of torsion they are able to withstand, and are not equipped to handle torsion levels above a certain threshold. 
     Some air springs fail when exposed to a high-torsion event (i.e., greater than ±1.25°), one type of failure is a rupture in the bellow, resulting in leakage in the air spring. 
     Accordingly, there exists a need for an air spring assembly which is able to tolerate increased levels of torsion induced by vehicle kinematics. 
     SUMMARY OF THE INVENTION 
     The present invention is an air spring assembly for a vehicle which allows a damper body to decouple from the air spring, allowing the damper to rotate freely without inducing torsion into the bellow. 
     The design of the air spring assembly of the present invention functions to decouple the piston from the damper. The design includes a two-piece piston having both an inner piston and an outer piston which are connected together, and a portion of the inner piston is positioned over the damper tube. The piston having the two-piece design of the present invention allows for the two-piece piston to fully decouple from the damper without leakage. The inner piston retains a rotary O-ring which seals to a damper rod to keep air within the air spring assembly. The air spring assembly of the present invention also includes a thrust bearing which is located between the inner piston and the top surface of the damper tube, where the thrust bearing allows full decoupling from the inner piston and the damper. The configuration of the two-piece piston and the thrust bearing ensure that there is no torsion translated to the bellow. 
     In one embodiment, the present invention is an air spring assembly which includes a damper body, and a damper rod partially extending into the damper body, where the damper rod is able to move relative to the damper body. The air spring assembly also includes an inner piston, an outer piston connected to the inner piston, and a portion of the damper body is surrounded by the inner piston. The air spring assembly also includes a bearing pressed between the damper body and the inner piston, and the bearing allows for rotation of the damper body relative to the piston assembly and the damper rod, preventing torsion from being transferred from the damper body to the piston assembly and into the bellow. 
     In one embodiment, the bearing includes an inner race wall portion connected to the inner piston, and an outer race wall portion located on and connected to the top surface of the damper body. At least one bearing member is disposed between the inner race wall portion and the outer race wall portion, and the at least one bearing member allows the outer race wall portion and the damper body to move relative to the inner race wall portion, the inner piston, and outer piston. 
     In one embodiment, the inner piston includes a main body portion, a groove integrally formed with the main body portion, and a seal disposed in the groove. The seal is in contact with the damper rod such that the seal prevents air from leaking out of the air spring assembly as the damper rod moves relative to the damper body. The inner piston also includes a cylindrical flange portion integrally formed with the main body portion, and a portion of the cylindrical flange portion circumscribes the bearing and the damper body. 
     In one embodiment, the outer piston includes a plurality of flange portions, and each of the plurality of flange portions is connected to the cylindrical flange portion of the inner piston. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a sectional view of an air spring assembly, according to embodiments of the present invention; 
         FIG. 2  an enlarged view of a portion of a sectional view of an air spring assembly, according to embodiments of the present invention; 
         FIG. 3  is a sectional view taken along lines  3 - 3  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     An air spring assembly having a decoupling mechanism according to the present invention is shown in the Figures, generally at  10 . Referring to the Figures generally, the air spring  10  includes a damper body  12 , and surrounding a portion of the damper body  12  is a piston, shown generally at  14 . The piston  14  may be manufactured as a single unitary component or multiple components. In the embodiment shown in the Figures, the piston  14  is a piston assembly  14  which includes an inner piston  14   a  connected to an outer piston  14   b , where both the inner piston  14   a  and the outer piston  14   b  are made from an injection molded material, such as an injection molded plastic material, but it is within the scope of the invention that the inner piston  14   a  and the outer piston  14   b  may be made of other materials, such as, but not limited to, metal, such as steel, or aluminum. The inner piston  14   a  and the outer piston  14   b  may also be made using different manufacturing processes other than injection molding, such as metal injection molding, casting, sintering, or stamping. 
     Extending into the damper body  12  is a damper rod  16 , such that the damper body  12  is able to move relative to the damper rod  16 . The air spring  10  also includes a bellow  18 , which is flexible and able to change shape as the piston assembly  14  is moved relative to the damper rod  16 . A free end  20  of the bellow  18  is clamped between a clamping ring  22  and a portion of the outer piston  14   b . A portion of the outer piston  14   b  is overmolded around a support ring  22   a , which is used to provide support against the force of the clamping ring  22  on the bellow  18  and the portion of the outer piston  14   b  to which force is applied by the clamping ring  22 . 
     The bellow  18  includes a cavity, shown generally at  24 , which is generally filled with air. The bellow  18  is partially surrounded by a guide tube  26 , and the guide tube  26  and the bellow  18  are connected to a top cap  28 . The top cap  28  includes a base portion  30 , and extending through an aperture  32  in the base portion  30  is the damper rod  16 . The damper rod  16  also extends through a jounce bumper  34 , which is partially surrounded by, and connected, to the top cap  28 . 
     The top cap  28  also has a cavity, shown generally at  36 , which is in fluid communication with the cavity  24  of the bellow  18 . The piston assembly  14  also includes a cavity, shown generally at  14   c , which is formed by the assembly of the inner piston  14   a  and the outer piston  14   b . The cavities  24 , 36 , 14   c  define a volume which changes as the piston assembly  14  and damper  12  move relative to the damper rod  16 . 
     The top cap  28  is connected to another component of the vehicle, such as the frame of the vehicle, but it is within the scope of the invention that the top cap  28  may be connected to other components of the vehicle as well. Additionally, the damper body  12  is connected to another part of the suspension system of the vehicle, such as an A-arm, or swing arm. As the A-arm moves from (operation of the vehicle) the damper body  12  and piston  14  move in either of the directions indicated by arrow  38  relative to the damper rod  16 . 
     As the vehicle is in operation, and travelling, there may be instances where the vehicle kinematics induce torsion into the air spring assembly  10 . 
     The air spring assembly  10  includes a decoupling mechanism, where the piston assembly  14  is part of the decoupling mechanism. The decoupling mechanism reduces or eliminates the transfer of torsion from the damper body  12  to the piston assembly  14 . The decoupling mechanism includes a bearing, shown generally at  42 , which in this embodiment is a thrust bearing  42 . The thrust bearing  42  includes an inner race wall portion  42   a , an outer race wall portion  42   b , and a plurality of bearing members  42   c  disposed between the inner race wall portion  42   a  and outer race wall portion  42   b . The inner race wall portion  42   a  is in contact with a bottom surface of the inner piston  14   a , and the outer race wall portion  42   b  is in contact with the top surface  12   a  of the damper body  12 . 
     The inner piston  14   a  includes main body portion  44   a , and a cylindrical flange portion  44   b  integrally formed with the main body portion  44   a , where the cylindrical flange portion  44   b  extends downwardly along the outer surface of the damper body  12  such that the cylindrical flange portion  44   b  partially circumscribes the damper body  12 . The inner piston  14   a  also includes a groove  46  formed as part of the main body portion  44   a , and disposed in the groove  46  is a seal  48 , which in this embodiment is an O-ring. The O-ring  48  is made of any suitable material which is capable of withstanding rotation and abrasion and maintain a seal. The O-ring  48  is in contact with the damper rod  16 , and prevents air from escaping the cavities  24 , 36 , 14   c , even as the damper rod  16  moves relative to the O-ring  48 . The inner piston  14   a  is also positioned such that there is a clearance  50  between the cylindrical flange portion  44  and the damper body  12 , such that the damper body  12  and the cylindrical flange portion  44  do not contact each other. 
     Referring to  FIGS. 2-3 , the outer piston  14   b  includes a plurality of flange portions  52   a , 52   b , 52   c , 52   d , 52   e  which are connected to the cylindrical flange portion  44  through an attachment feature  54 . In one embodiment, the attachment feature  54  is a hot gas weld, but it is within the scope of the invention that other types of attachment features may be used, such as, but not limited to, an ultrasonic weld or a laser weld. The attachment feature  54  is only connected to part of each flange portion  52   a , 52   b , 52   c , 52   d , 52   e , and the remainder of each flange portion  52   a , 52   b , 52   c , 52   d , 52   e  is in contact with the outer surface of the cylindrical flange portion  44   b  of the outer piston  14   b . The attachment feature  54  circumscribes the cylindrical flange portion  44   b , such that the attachment feature  54  also connects a bottom flange portion  58  to the cylindrical flange portion  44   b . Each of the plurality of flange portions  52   a , 52   b , 52   c , 52   d , 52   e  are integrally formed with an outer shell portion  56  of the outer piston  14   b . The outer shell portion  56  also includes a contour shell portion  56   a , which the contour shell  56   a  defines a portion of the shape of the bellow  18  as the bellow  18  moves during operation of the air spring assembly  10 . 
     The air spring assembly  10  also includes a flexible outer cover, which in this embodiment is a gaiter (not shown). The gaiter is connected to the guide tube  26 , and to a connector which is part of the damper body  12 . The gaiter flexes and moves as the damper body  12  and moves during travel of the vehicle. 
     During vehicle travel, there are instances where torsion is induced to the air spring assembly  10 . This torsion is typically induced to the air spring assembly  10  as the damper body  12  is subjected to different torsions from other components in the suspension system. The damper body  12  and the outer race wall portion  42   b  of the bearing  42  rotate relative to the piston assembly  14  and the inner race wall portion  42   a  of the bearing  42 . 
     Because the damper body  12  moves relative to the damper rod  16 , the piston assembly  14  also moves relative to the damper rod  16  in the same manner. The seal  48  is therefore in frictional contact with the damper rod  12 , where the seal  48  prevents air from exiting the cavities  24 , 36 , 14   c . The bearing  42  facilitates the rotation of the piston assembly  14  relative to the damper body  12 , and because the damper body  12  is able to rotate relative to the piston assembly  14 , this relative movement reduces or eliminates the torsion that is induced to the piston assembly  14  from the damper body  12  by other suspension system components. 
     While the bearing  42  has been described, it is within the scope of the invention that other types of components may be used, such as, but not limited to, a ball bearing, a needle bearing, a journal bearing, a bushing, or the like. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.