Patent Publication Number: US-2022212527-A1

Title: Subframe and suspension assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/373,213, filed Aug. 10, 2016, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     Field 
     The present disclosure is generally directed to automotive subframe and suspension assemblies. More particularly, disclosed herein is a rear subframe for an electric vehicle capable of housing one or two electric motors for an electric vehicle. Additional components such as invertors may also be housed within the subframe. A rear suspension and steering system may also be included. 
     Description of the Related Art 
     Subframes may be used to protect and isolate the motor from the main vehicle frame. Such subframes may improve safety and reduce vibrations. Independent suspensions systems allow for each wheel of the vehicle to move independently of one another. Active adjustment of the rear wheels reduces a vehicle&#39;s turning radius and stabilizes vehicle handling at high speeds. 
     SUMMARY 
     The devices, systems, and methods disclosed herein have several features, no single one of which is solely responsible for its desirable attributes. Without limiting the scope as expressed by the claims that follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of the system and methods provide several advantages over traditional systems and methods. 
     In some implementations, a system for housing at least one an electric motor in an electric automobile includes a rear subframe. The subframe may include at least two castings extending in a longitudinal direction and spaced apart from one another in a lateral direction. The at least two castings may be coupled together by a laterally extending front cross-car extrusion and a laterally extending rear cross-car extrusion. The rear cross-cross car extrusion may be spaced away from the front cross-car extrusion in the longitudinal direction to define an area that is bounded by the at least two castings, the laterally extending front cross-car extrusion, and the laterally extending rear cross-car extrusion. A laterally extending roll bar may be coupled to the at least two castings and positioned over the area to define a motor receiving volume configured to receive at least one motor inserted over the front cross-car extrusion. At least two braces may be removably couplable to the subframe. The at least two braces may be configured to prevent removal of a motor inserted over the front cross-car extrusion when the at least two braces are coupled to the subframe. 
     In some aspects, the at least two castings include at least a portion of a motor mount configured secure the motor with respect to the castings. A rear steering actuator may be coupled to the rear cross-car extrusion. Two laterally extending track rods may be coupled to opposite sides of the rear steering actuator. The track rods may include at least one section that curves in the longitudinal direction. The track rods may be coupled to two different knuckles with a pin that extends upward through an underside of the knuckle. A lower semi-trailing arm may be hingedly connected to each casting and may support an air spring from below. Two upper control arms may be hingedly connected to each casting and may extend laterally away from the casting and positioned in-line with the cross-car roll bar when viewed from above. 
     In some implementations, a rear subframe and rear steering assembly system includes at least two castings extending in a longitudinal direction and spaced apart from one another in a lateral direction. The at least two castings may be coupled together by a laterally extending front cross-car extrusion and a laterally extending rear cross-car extrusion. The rear cross-cross car extrusion may be spaced away from the front cross-car extrusion in the longitudinal direction to define an area that is bounded by the at least two castings, the laterally extending front cross-car extrusion, and the laterally extending rear cross-car extrusion. A laterally extending roll bar may be coupled to the at least two castings and positioned over the area to define a motor receiving volume configured to contain at least one motor. A rear steering actuator may be mounted to a rear facing surface of the rear cross-cross car extrusion. 
     In some aspects, two track rods are coupled to opposite sides of the rear steering actuator and extend laterally away from the rear steering actuator. The track rods may include at least one curved section extending in the longitudinal direction. The two track rods may each be coupled to two different knuckles with a pin that extends upward through an underside of the knuckle. The steering knuckles may include a wheel mount. In some aspects, the track rods are coupled to the steering knuckles at a location below the center of the wheel mount when the viewed in the lateral direction. The steering knuckles may include a rear lever portion extending in the longitudinally direction and coupled to one of the track rods. The steering knuckles may be coupled to the castings with at least one lower semi-trailing arm. A wind-up link may connect the steering knuckle to the lower semi-trailing arm. The wind-up link may be positioned behind the rear lever portion of the knuckle when the viewed in the lateral direction. 
     In some implementations a method of installing an electric motor in a rear subframe includes inserting at least one electric motor into a front side of a rear subframe configured to at least partially surround the electric motor on all sides except for the front side. The method may include securing at least two braces to the subframe to close the front end and at least partially surround the electric motor on all sides. The method may include securing the electric motor to at least a portion of a motor mount that is built into the subframe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following is a brief description of each of the drawings. From figure to figure, the same reference characters have been used to designate the same components of an illustrated embodiment. The drawings disclose illustrative embodiments and particularly illustrative implementations in the context of an electric automobile. They do not set forth all embodiments. Other embodiments may be used in addition to or instead. Conversely, some embodiments may be practiced without all of the details that are disclosed. 
       It is to be noted that the figures provided herein are not drawn to any particular proportion or scale, and that many variations can be made to the illustrated embodiments. Brief introductions to some of the features, which are common to the described embodiments, are now described. 
         FIG. 1  is front top perspective view of a subframe according to one implementation. 
         FIG. 2  is rear bottom perspective view of the subframe of  FIG. 1 . 
         FIG. 3  is rear perspective view of the subframe of  FIG. 1 . 
         FIG. 4  is an overhead view of the subframe of  FIG. 1 . 
         FIG. 5  is an underside view of the subframe of  FIG. 1 . 
         FIG. 6  is a rear view of the subframe of  FIG. 1 . 
         FIG. 7  is a front view of the subframe of  FIG. 1 . 
         FIG. 8  is a right side view of the subframe of  FIG. 1 . 
         FIG. 9  is the same as  FIG. 1  with the two bolt-in braces removed. 
         FIG. 10  is the same as  FIG. 9  with two electric motors shown as being placed within the subframe in a direction that runs from the front to the rear of the vehicle. 
         FIG. 11  is the same as  FIG. 10  with two electric motors installed within the subframe. 
         FIG. 12  is the same as  FIG. 11  with the two bolt-in braces secured to the subframe to secure the two electric motors in the subframe. 
         FIG. 13  is the same as  FIG. 1  with a drive system, steering system, and suspension system coupled to the subframe. 
         FIG. 14  is a rear perspective view of  FIG. 13 . 
         FIG. 15  is an underside view of  FIG. 13 . 
         FIG. 16  is an overhead view of  FIG. 13 . 
         FIG. 17  is a perspective view of left side of the steering system and suspension system. 
         FIG. 18  is an underside view of  FIG. 17 . 
         FIG. 19  is an overhead view of  FIG. 17 . 
         FIG. 20  is a head on view of  FIG. 17 . 
         FIG. 21  is a rear perspective view of the steering system and suspension system of  FIG. 17  coupled to the subframe of  FIG. 1 . 
         FIG. 22  is an underside view of  FIG. 21 . 
         FIG. 23  is an overhead view of  FIG. 21 . 
         FIG. 24  is a front view of  FIG. 21 . 
         FIG. 25  is a head on view of  FIG. 21 . 
         FIG. 26  is a partial perspective view of the underside of a vehicle having the subframe, drive system, steering system, and suspension system of  FIG. 13  coupled to the frame of a vehicle. 
         FIG. 27  is front top perspective view of an alternative subframe, similar to the subframe shown in  FIG. 1  according to one implementation. 
         FIG. 28  is rear bottom perspective view of the subframe of  FIG. 27 . 
         FIG. 29  is rear perspective view of the subframe of  FIG. 27 . 
         FIG. 30  is an overhead view of the subframe of  FIG. 27 . 
         FIG. 31  is an underside view of the subframe of  FIG. 27 . 
         FIG. 32  is a rear view of the subframe of  FIG. 27 . 
         FIG. 33  is a front view of the subframe of  FIG. 27 . 
         FIG. 34  is a right side view of the subframe of  FIG. 27 . 
         FIG. 35  is the same as  FIG. 27  with additional components coupled to the subframe, which may be coupled to a drive system (not shown) as similarly shown and described with respect to  FIG. 13 . 
         FIG. 36  is a rear perspective view of  FIG. 35 . 
         FIG. 37  is an underside view of  FIG. 35 . 
         FIG. 38  is an overhead view of  FIG. 35 . 
         FIG. 39  is a perspective view of left side of the steering system and suspension system. 
         FIG. 40  is an underside view of  FIG. 39 . 
         FIG. 41  is an overhead view of  FIG. 39 . 
         FIG. 42  is a head on view of  FIG. 39 . 
         FIG. 43  is a rear perspective view of the steering system and suspension system of  FIG. 39  coupled to the subframe of  FIG. 27 . 
         FIG. 44  is an underside view of  FIG. 43 . 
         FIG. 45  is an overhead view of  FIG. 43 . 
         FIG. 46  is a front view of  FIG. 43 . 
         FIG. 47  is a head on view of  FIG. 43 . 
         FIG. 48  is a partial perspective view of the subframe, steering system, and suspension system of  FIG. 35 , which may be coupled to a frame of a vehicle, as similarly shown in  FIG. 26 . 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein is a subframe assembly for housing one or two relatively large electric motors. As such, the same subframe may be used for various models of electric vehicles. For example, a single motor may be mounted in the subframe for one line of production vehicles and a second, higher performance line of production vehicles, may include two motors mounted within the same subframe. The subframe may be mounted into various vehicle frames. In this way, a more modular vehicle construction may be possible. In embodiments with a single motor, a differential may also be housed within the subframe. The motor(s) may include gear sets. 
     The subframe may include a substantially unitary construction. For example, the subframe may include very few parts that are not bonded or welded together. For example, the subframe may include at least two longitudinal members that are joined together with two or more lateral, cross-car members that are welded to the longitudinal members. Such a unitary construction may increase the strength of the subframe and protect the motors within the subframe. Such a construction may also provide the relatively large space required for two large rear motors, two gear sets, and two invertors. In some aspects, the subframe is configured to contain the motor and other components within the subframe during collisions. The subframe may surround the drive train components and protect the drive train components from impacts in multiple directions and during roll-overs. 
     In some implementations, the subframe is configured such that the one or more motors are inserted into the front side of the subframe during a motor installation. Two or more bolt-in braces may then be installed to secure the motors within the subframe. After the bolt-in braces are installed, the subframe may substantially surround and house the one or more motors within the subframe. The bolt-in braces may be the only portions of the subframe that are easily removed and re-attached. In other implementations, for example, the implementation shown with respect to at least  FIG. 27 , the braces may be permanently affixed to the subframe, or formed as a solid pieces in conjunction with the subframe. 
     In some implementations, the subframe includes one or more built-in motor mounts. In this way, the motor(s) may be more easily installed and secured within the subframe. Thus, the present disclosure provides a means for securing one or more motors on and within the subframe. In some aspects, the subframe supports at least a portion of one or more motors from below. In some aspects, the subframe inhibits the movement of the one or motors in the lateral, longitudinal, and transverse directions. 
     The subframe may include at least one rear cross-car extrusion. Such a rear cross-car extrusion may increase the rigidity of the subframe. In some aspects, a rear steering actuator may be mounted on the rear cross-car extrusion. Thus, the cross-car extrusion may simplify manufacturing. 
     The subframe may include at least one rear cross-car roll bar that is configured to pass over at least a portion of at least one motor placed within the subframe when viewed from above. In some aspects, the subframe includes one front cross-car extrusion. A subframe constructed of just two uniquely shaped castings coupled together by only three cross-car members may provide a cost effective, easy to manufacture, and robust system for housing a drive train. Furthermore, the subframe may be configured such that a rear steering and suspension system may be easily attached thereto. 
     A suspension system may be coupled to the subframe. The suspension system may include semi-trailing arms that move at an angle to the vehicle&#39;s longitudinal axis as they deflect and rebound during driving. Such semi-trailing arms may improve handling during cornering. 
     In some aspects, an air spring is mounted to each semi-trailing arm. The air spring may be capable of adjusting the ride height of the vehicle and/or providing a smoother and more comfortable ride for the passengers. In some aspects, each semi-trailing arm may be configured to accommodate an air spring that is large enough to raise and lower the relatively heavy electric motor(s). Furthermore, the semi-trailing arm design disclosed herein allows for large air springs while at the same time attempts to minimize the size of the semi-trailing arms in at least the lateral direction. 
     The terms “upper,” “lower,” “top,” “bottom,” “underside,” “upperside” and the like, which may be used to describe the components described herein, are used in reference to the illustrated orientation of the embodiment. The “front” of the subframe  100  generally refers to the left hand side of the subframe  100  positioned in the orientation in  FIG. 1 . The “rear” of the subframe  100  generally refers to the right hand side of the subframe  100  positioned in the orientation in  FIG. 1 . 
     The foregoing description and claims may refer to elements or features as being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one element/feature is directly or indirectly connected to another element/feature. Likewise, unless expressly stated otherwise, “coupled” means that one element/feature is directly or indirectly coupled to another element/feature. Thus, although the various schematics shown in the figures depict example arrangements of elements and components, additional intervening elements, devices, features, or components may be present in an actual embodiment (assuming that the functionality is not adversely affected). Furthermore, various solutions, other than those expressly described herein may be used to mechanically couple the disclosed components. Such couplings include ball and socket joints, hinges, universal joints, swivel joints, and the like. 
       FIGS. 1-8  illustrate an exemplary implementation of a subframe  100 . To assist in the description of the subframe  100  and related components, the following coordinate system may be used (see, e.g.,  FIG. 1 ). A “longitudinal axis” is generally parallel to a length-wise axis extending from the rear of the subframe  100  to the front of the subframe  100 . The “longitudinal direction” refers to a direction substantially parallel to the longitudinal axis. When installed in a vehicle, the subframe  100  would travel in the forward direction from right to left in  FIG. 1 , along the longitudinal axis. 
     The subframe  100  includes a front portion and a rear portion. As shown in  FIG. 1 , the front cross-car extrusion  101  may be located in the front portion of the subframe  100  and the rear cross-car extrusion  107  may be located in the rear portion of the subframe  100 . The front cross-car extrusion  101  may be parallel to the rear cross-car extrusion  107 . The front cross-car extrusion  101  and the rear cross-car extrusion  107  may be spaced apart from each other in the longitudinal direction. Additional cross-car extrusions or members may be utilized. 
     A “lateral axis” is normal to the longitudinal axis and is generally parallel to a width-wise axis extending from the right side of the subframe  100  to the left side of the subframe  100 . The “lateral direction” refers to a direction substantially parallel to the lateral axis. As shown, the lateral axis is parallel to the front and rear cross-car extrusions  101 ,  107 . The lateral axis is also parallel to the cross-car roll bar  103 . 
     A “transverse axis” extends normal to both the longitudinal axis and the lateral axis and is generally parallel to a height-wise axis extending from the bottom of the vehicle to the top of the vehicle. The “transverse direction” refers to a direction substantially parallel to the transverse axis. Thus, the rear cross-car extrusion  107  has a height that extends in the transverse direction. The cross car roll bar  103  is generally spaced apart from the front and rear cross-car extrusions  101 ,  107  by a distance in the transverse direction. 
     The subframe  100  includes a right portion and a left portion. As shown in  FIG. 1 , the right casting  102   a  may be located in the right portion of the subframe  100  and the left casting  102   b  may be located in the left portion of the subframe  100 . The right casting  102   a  may be generally parallel to the left casting  102   b  and generally parallel to the longitudinal axis. 
     Continuing with  FIGS. 1-8 , the right and left bolt-in braces  105   a,    105   b  are shown in the installed position. As shown, the right bolt-in brace  105   a  is coupled at one end to a lower front section of the right casting  102   a  and coupled at the other end to a top central section of the right casting  102   a  that is adjacent to the top cross car rod  103 . Similarly, the left bolt-in brace  105   b  is coupled at one end to a lower front section of the left casting  102   b  and coupled at the other end to a top central section of the left casting  102   b  that is adjacent to the top cross car rod  103 . The bolt-in braces  105   a,    105   b  may be removeably coupled to the subframe  100  using one or more bolts or other couplings. While two bolt-in braces  105   a,    105   b  are shown and described, additional bolt-in braces may be included. 
     The left and right castings  102   a,    102   b  may include one or more built-in receiving spaces  110   a,    110   b,    112   a,    112   b,    113   a,    113   b  for one or more suspension components. For example, a lower semi-trailing arm may be coupled to the lower receiving spaces  110   a,    110   b,    112   a,    112   b  and an upper control arm may be coupled to the upper receiving spaces  113   a,    113   b.    
     As best shown in  FIG. 8  the castings  102  include a lower and frontward most mount  122   a  and the castings then extend rearward along the longitudinal axis. The frontward most mount  122   a  may be configured to be coupled to a vehicle body. Such mounts may include bushings. 
     Continuing with the castings  102 , extending rearward along the longitudinal axis away from the frontward most mount  122   a,  the casting  102  may include a transverse portion  140  that splits into a rearward most mount  142   a  and an archway portion  150 . The rearward most mount  142   a  may include a mount extending along the longitudinal axis. The rearward most mount  142   a  may be configured to the coupled to the vehicle body. As shown, the rearward most mount  142   a  may be spaced apart in the transverse direction as compared to the lower and frontward most portion  122   a.    
     The archway portion  150  may terminate at a receiving area for the right bolt-in brace  105   a.  The right bolt-in brace  105   a  may be removably attached to the casting  102  in at least two places. The bolt-in brace  105   a  may extend along the transverse and/or longitudinal axis and connect the archway portion  150  of the casting  102  to the lower portion of the casting  102  that extends along the longitudinal axis. With the bolt-in brace  105   a  coupled to the casting  102 , an enclosure  190  for one or more motors may be formed. The bolt-in braces  105  may be reinforced by a gusset  159 . 
     Turning to  FIG. 9 , the subframe  100  is shown with the bolt-in braces  105  removed. A receiving area for one or more motors may be defined by the area inside the perimeter formed by the left and right castings  102   a,    102   b  and the front and rear cross-car extrusions  101 ,  107 . 
     The subframe  100  may be configured to receive one or more motors that are inserted through the front of the subframe  100 . That is to say, the subframe  100  is configured such that the drivetrain components (e.g. the one or two electric motors) may only be inserted into the subframe  100  from the front—passing at least partially over the front cross-car extrusion  101 . As shown, the shape of the rear cross-car extrusion  107  may prevent the insertion of a motor through the rear of the subframe  100 . In some aspects, the rear cross-car extrusion  107  may prevent or inhibit movement of a motor that is inserted into the subframe  100  in at least the longitudinal direction. 
     The cross-car roll bar  103  may extend over the receiving area for the one or more motors to define a motor receiving volume. The cross-car roll bar  103  may be fixedly coupled to the left and right castings  102   a,    102   b.  In some aspects, the cross-car roll bar  103  may prevent or inhibit movement of a motor that is inserted into the subframe  100  in at least the transverse direction. 
     The subframe  100  may include one or more motor mounts  200 . The motor mounts  200  may be configured to receive at least a portion of the motor or other motor mount component. As shown in  FIG. 9 , the motor mounts  200  may be formed into the castings  102   a,    102   b.  In this way, the motors may be secured to the subframe  100  using with only a few components that are at least partially built-in to the subframe  100 . 
     As shown in  FIG. 10 , at least two motors  150   a,    105   b  and at least two invertors  230   a,    230   b  may be inserted over the front cross-car extrusion  101  and into the motor receiving volume. Brackets  225   a,    225   b  may be coupled to the motors  150   a,    105   b  which are in turn coupled to the motor mounts  200  to secure the motors  150   a,    105   b  within the motor receiving volume. 
     Turning to  FIG. 11 , the two motors  150   a,    105   b  and two invertors  230   a,    230   b  are shown within the subframe  100  and secured to the motor mounts  200 . The motor mounts may help prevent or inhibit movement of the motors  150   a,    150   b  with respect to the subframe  100  in all three directions. While two motors are shown in  FIG. 11 , one motor  105   a  may be sufficient. 
       FIG. 12  illustrates the two motors  150   a,    105   b  and two invertors  230   a,    230   b  secured within the subframe  100  and with bolt-in braces  105  coupled to the subframe  100 . The braces  105   a,    105   b  may be configured to prevent removal of the one or more motors from the subframe  100 . Thus, the braces  105   a,    105   b  may help prevent or inhibit movement of the motors  150   a,    150   b  with respect to the subframe  100  in at least the longitudinal and transverse directions. As shown, the cross-car roll bar  103  extends over the two motors  150   a,    105   b.    
     While the bolt-in braces  105   a,    105   b  are shown as connecting two portions of each casting  102   a,    102   b,  the bolt-in braces  105   a,    105   b  may be configured such that they are removably couplable to a portion of a casting  102   a,    102   b  at one end and to a portion of the cross-car roll bar  103  at the other end of the brace. In other implementations, the bolt-in braces  105   a,    105   b  are removably couplable to the front cross-car extrusion  101  at one end and to the cross-car roll bar  103  at the other end of the brace. In other implementations, the bolt-in braces  105   a,    105   b  are removably couplable to the front cross-car extrusion  101  at one end and to a portion of a casting  102   a,    102   b  at the other end of the brace. Additional bolt-in braces  105   a,    105   b  may be utilized. For example, a third bolt-in brace (not shown) may be removably couplable to a center portion of the cross-car extrusion  101  at one end and to a center portion of the cross-car roll bar  103  at the other end of the brace, to further house the motor(s) within the subframe  100 . 
     Turning to  FIGS. 13-16 , a rear steering system and an independent rear suspension system may be coupled to the subframe  100 . The steering system generally includes a steering actuator  300  that is mounted to the rear cross-car extrusion  107 . As shown, the steering actuator  300  is coupled to a rear facing surface of the rear cross-car extrusion  107 . 
     The steering actuator  300  includes two couplings  305  at opposite ends. In some implementations, the steering actuator  300  is an active kinematics control actuator available from the ZF Company. The couplings  305  may be connected to track rods  310  which are in turn coupled to the left or right rear wheel steering knuckles  400 . Thus, the steering actuator  300  may push or pull on the track rods  310  to rotate the steering knuckles  400  and turn the rear wheels as desired. 
     The steering knuckles  400  may include a wheel mount  450 . The wheel mount  450  may be coupled to an axle  475  which is coupled to an electric motor  150   a,    150   b.  The steering knuckles  400  may be coupled to the subframe  100  with an upper control arm  370  and a lower semi-trailing arm  600 . Each steering knuckle  400  may also be coupled to the lower semi-trailing arm  600  with a wind-up link  350 . A damper  550  may also be coupled to the steering knuckle  400 . The lower semi-trailing arm  600  may support an air spring  500  from below. The air spring  500  may be configured to adjusting the ride height of the vehicle. 
     As shown in  FIG. 16 , the upper control arms  370  may be positioned substantially in-line with the cross-car roll bar  103  when the subframe  100  is viewed from above. In other words, the upper control arms  370  may extend in a substantially straight line along the lateral axis away from either side of the castings  102   a,    102   b  from a location that is adjacent to the location where the cross-car roll bar  103  is connected to the castings  102   a,    102   b  when the subframe  100  is viewed from above. 
     The upper control arms  370  may be hingedly coupled to the castings  102   a,    102   b  such that they can rotate up and down with respect to the subframe  100  in the transverse direction. For example, the upper control arms  370  may include knuckles  321  at either end. One control arm knuckle  321  may be inserted into the left of right upper receiving spaces  113   a,    113   b  on the casting and secured within the receiving spaces  113   a,    113   b  with a pin. The control arm knuckles  321  on the opposite side of the control arms  370  may be inserted to into the upper receiving spaces  415  of each steering knuckle  400  and secured with a pin. In this way, the upper control arms  370  and the knuckles  321  may be movable with respect to the subframe  100  in at least the transverse direction. 
     As also seen in  FIGS. 18-19 , the track rods  310  may be shaped to accommodate an air spring  500 . As such, the track rods  310  may not be substantially linear rods. Rather the track rods  310  may include one or more curved sections to bend around the relatively large air springs  500  required for such a relatively heavy load within the subframe  100 . 
     With reference to  FIGS. 18-20 , the track rods  310  may be hingedly coupled to the steering actuator  300  such that the track rods  310  may be able to rotate with respect to the steering actuator  300  about a connection point between the track rod  310  and the steering actuator  300  in at least the transverse direction. In some aspects, the steering actuator  300  includes a leaf  305  configured to receive a track rod knuckle  320 . The steering actuator leaf  305  may be coupled to the track rod knuckle  320  with a pin. 
     As best shown in  FIG. 20 , the track rods  310  may include a track rod pin  390  at the end that is opposite to the end that terminates in the track rod knuckle  320 . The track rod pin  390  may extend away from the track rod  310  in the transverse direction. The track rod pin  390  may be inserted upwardly into an opening in a rearward, longitudinally extending lever portion  490  of the steering knuckle  400 . Thus, the steering knuckle  400  may be rotated with respect to the track rods  310  when the track rod moves in the lateral direction. In some aspects, the longitudinally extending lever portion  490  of the steering knuckle  400  is positioned below a longitudinally extending line passing through the transverse center of the wheel mount  450 . 
     As shown, for example, in  FIGS. 18 &amp; 22 , the lower semi-trailing arm  600  may be coupled to the subframe  100  at two spaced apart locations. The lower semi-trailing arm  600  may also be configured to pivot about at least two connection points with the castings  102   a,    102   b.  For example, the lower semi-trailing arm  600  may include a front semi-trailing arm knuckle  612  and a rear semi-trailing arm knuckle  610 . The lower semi-trailing arm  600  may include a vent  625  on the configured to draw in and/or expel air from the air spring  500  positioned on the lower semi-trailing arm  600 . 
     The rear semi-trailing arm knuckle  610  may be inserted into receiving space  110   a,    110   b  on the castings  102   a,    102   b.  The rear semi-trailing arm knuckle  610  may be secured to the receiving space  110   a,    110   b  by a pin. Such as connection may allow for the lower semi-trailing arm  600  to pivot with respect to the subframe  100  in at least the transverse direction. The rear semi-trailing arm knuckle  610  may thus pivot about the longitudinal axis. 
     The front semi-trailing arm knuckle  612  may be inserted into receiving space  112   a,    112   b  on the castings  102   a,    102   b.  The front semi-trailing arm knuckle  612  may be secured to the receiving space  112   a,    112   b  by a pin. Such as connection may allow for the lower semi-trailing arm  600  to pivot with respect to the subframe  100  in at least the transverse direction. As shown, the axis of rotation of the front semi-trailing arm knuckle  612  may be offset from the longitudinal axis by an angle θ. In some implementations, this angle ζ is 30°. However, the angle θ may be any suitable angle. For example, the angle θ may be between 15° and 45°. 
     The lower semi-trailing arm  600  may also be coupled to the steering knuckle  400  at two spaced apart locations. For example, the lower semi-trailing arm  600  may include an outside knuckle  620  that is inserted into a lower leaf  425  in the steering knuckle  400  and secured with a pin. 
     A wind-up rod  350  may also be used to couple the lower semi-trailing arm  600  to the steering knuckle  400 . One end of the wind-up rod  350  may include a mount that is inserted into a leaf  650  on an outward edge that is positioned rearward of the outside knuckle  620 . The other end of the wind-up rod  350  may include an opening for receiving a pin  470  extending from the steering knuckle  400 . As shown in  FIG. 20 , the wind-up rod  350  may be generally parallel with the transverse axis and may be positioned behind the longitudinally extending lever portion  490  of the steering knuckle  400  when viewed in the lateral direction. 
       FIG. 26  illustrates the subframe, drive system, steering system, and suspension system described above installed in the rear of a vehicle. As shown, the mounts  122   a,    122   b,    142   a,    142   b  are coupled to the underside of a vehicle&#39;s frame. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     It is to be understood that the implementations are not limited to the precise configuration and components illustrated above. Various modifications, changes, and variations may be made in the arrangement, operation, and details of the methods and apparatus described above without departing from the scope of the implementations. 
     Although this invention has been described in terms of certain embodiments, other embodiments that are apparent to those of ordinary skill in the art, including embodiments that do not provide all of the features and advantages set forth herein, are also within the scope of this invention. Moreover, the various embodiments described above can be combined to provide further embodiments. In addition, certain features shown in the context of one embodiment can be incorporated into other embodiments as well.