Patent Publication Number: US-2023150574-A1

Title: Support structure for vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a support structure for vehicle having a structure that induces fracture when an inadvertent external force is applied to a vehicle. 
     BACKGROUND ART 
     As shown in PTL 1 (JP-A-2014-91469), in order to maintain high rigidity in a support structure for vehicle (steering knuckle), strength is ensured by forming a first rib connecting a damper attachment portion and a tie-rod attachment portion, a second rib connecting a tie-rod attachment portion and a lower arm attachment portion, and a third rib for reinforcing these ribs. 
     The first rib, the second rib, and the third rib have a required width and height, and these ribs have a triangular shape in a front view, thereby increasing the strength of a support structure  20  for vehicle. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP-A-2014-91469 
     SUMMARY OF INVENTION 
     Technical Problem 
     Incidentally, in a support structure for vehicle such as a steering knuckle, for example, when an inadvertent external force is applied to a front side and an obliquely front side of the vehicle, a force in a front side direction or an obliquely front direction acts on the steering knuckle together with the wheel, the tie-rod attachment portion facing the rear of the vehicle faces a vehicle interior direction, and a member connected to the tie-rod attachment portion may enter a vehicle interior. 
     Solution to Problem 
     The present embodiment has been made to solve the above problem, and an object of the present embodiment is to provide a support structure for vehicle that ensures necessary strength and satisfies fracture strength at which the support structure for vehicle is broken when an inadvertent force is applied from the outside. 
     A support structure for vehicle according to the present embodiment includes a body portion attached to a wheel support, a damper attachment portion which is positioned above the body portion and to which a damper is attached, a tie-rod attachment portion that extends from the body portion in one of front and rear directions of the vehicle and to which a tie rod is attached, a lower arm attachment portion which is positioned below the body portion and to which a lower arm is attached, a first rib connecting the damper attachment portion with the tie-rod attachment portion, a second rib connecting the tie-rod attachment portion with the lower arm attachment portion, and a third rib connecting the first rib with the second rib, in which the first rib has a first inclined portion and a first thin portion that becomes a bottom portion of the first inclined portion by being inclined such that a height of the first rib gradually decreases from the damper attachment portion toward the tie-rod attachment portion, and the third rib includes a second inclined portion and a second thin portion which is a bottom portion of the second inclined portion by being inclined such that a height of the third rib gradually decreases from the second rib toward the first rib. 
     The first inclined portion and the second inclined portion may be formed such that the first thin portion and the second thin portion overlap each other when viewed from a side surface side of the body portion. 
     A through hole for attaching a wheel speed sensor may be formed in a side surface portion of the body portion in the vicinity of the first thin portion and the second thin portion. 
     Advantageous Effect 
     According to claim 1, while ensuring rigidity, when the tie-rod attachment portion positioned on the vehicle interior side is pushed from a vehicle front side to a vehicle interior side by an impact from the outside at the time of a vehicle collision or the like, the tie-rod attachment portion is fractured so as to be bent in a direction in which the tie rod does not enter the vehicle interior, and thus it is possible to suppress an influence on the vehicle interior. 
     According to claim 2, since a starting point of the fracture can be controlled, the fracture strength can be efficiently satisfied. 
     According to claim 3, the fracture starting point can be more easily controlled by forming the through hole for attaching a wheel speed sensor in a side surface portion in the vicinity of the first thin portion and the second thin portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       [ FIG.  1   ]  FIG.  1    is a front view of a support structure for vehicle according to the present embodiment. 
       [ FIG.  2   ]  FIG.  2    is a right side view of the support structure for vehicle according to the present embodiment. 
       [ FIG.  3   ]  FIG.  3    is a perspective view of the support structure for vehicle according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the invention will be described in detail. 
       FIG.  1    is a front view (a view seen from a vehicle side) of a support structure  20  for vehicle according to the present embodiment.  FIG.  2    is a right side view of the support structure  20  for vehicle.  FIG.  3    is a perspective view of the support structure  20  for vehicle. 
     The support structure  20  for vehicle (steering knuckle: hereinafter, simply referred to as knuckle) according to the present embodiment is made of aluminum, and is cast mainly by a gravity casting method. 
       FIGS.  1  to  3    show the knuckle  20  for a wheel which is a right front wheel. The knuckle for a left front wheel has a shape symmetrical to the knuckle  20  shown in  FIG.  1   . 
     Since a basic structure and function of the knuckle  20  are known, they will be briefly described below. 
     As shown in  FIG.  3   , the knuckle  20  has a recessed body portion  22  whose bottom portion is located on a wheel attachment portion side. A shaft hole  21  into which an axle of the wheel is rotatably fitted is formed in the center of the bottom surface of the recess of the body portion  22 . Four bolt holes  22   a ,  22   b ,  22   c ,  22   d  to which bolts of a wheel hub (not shown) serving as a wheel support are screwed and joined are formed in a bottom portion of the body portion  22  around the shaft hole  21 . 
     A plurality of support arms to which various members are connected extend from the body portion  22 . 
     A damper attachment portion  24  to which a damper (not shown) of a suspension is connected is formed at a distal end portion of a support arm  24   a  extending to an upper portion of the body portion  22 . 
     A tie-rod attachment portion  26  to which a tie rod (not shown) for transmitting a steering force from a steering wheel (not shown) is connected is formed at a distal end portion of a support arm  26   a  extending from the body portion  22  to any one of the front and rear directions of the vehicle (the rear side of the vehicle in  FIG.  1   ). 
     A lower arm attachment portion  28  to which a lower arm (not shown), which is a control arm of the suspension, is connected is formed in a lower portion of the body portion  22 . 
     Attachment holes  30   a  and  30   b  for attaching a brake caliper (not shown) are formed in a side surface portion of the body portion  22  opposite to the tie-rod attachment portion  26 . 
     A first rib  32  connecting the damper attachment portion  24  with the tie-rod attachment portion  26  is formed between the damper attachment portion  24  and the tie-rod attachment portion  26 . The first rib  32  has a required height and a required width when viewed from the bottom surface of the body portion  22 . 
     A second rib  34  connecting the tie-rod attachment portion  26  with the lower arm attachment portion  28  is formed between the tie-rod attachment portion  26  and the lower arm attachment portion  28 . The second rib  34  has a required height and a required width when viewed from the bottom surface of the body portion  22 . 
     The second rib  34  is formed to be wider than the first rib  32 . 
     A third rib  36  is formed between the first rib  32  and the second rib  34  so as to bridge the first rib  32  and the second rib  34 . The third rib  36  constitutes a part of a wall portion of the recessed body portion  22 . 
     A recess  38  is formed by casting in a region surrounded by the first rib  32 , the second rib  34 , and the third rib  36  so that these ribs have a required width. 
     The first rib  32 , the second rib  34 , and the third rib  36  having a required height and a required width form a structure having a triangular shape in a front view, and as a result, the required strength (rigidity) is ensured even in an aluminum knuckle having a strength lower than an iron knuckle. 
     Reference numeral  40  denotes a through hole for attaching a wheel speed sensor provided in the side surface portion of the body portion  22 . 
     In the present embodiment, the first rib  32  is formed with a first inclined portion  32   a  inclined such that the height gradually decreases from the damper attachment portion  24  toward the tie-rod attachment portion  26 , and a first thin portion  32   b  having a low height, which is a bottom portion of the first inclined portion  32   a , is formed. 
     The third rib  36  is formed with a second inclined portion  36   a  inclined such that the height gradually decreases from the second rib  34  toward the first rib  32 , and a second thin portion  36   b  serving as a bottom portion of the second inclined portion  36   a . 
     Therefore, when viewed from a side surface side of the knuckle  20  ( FIG.  2   ), an inclined surface of the first inclined portion  32   a  and an inclined surface of the second inclined portion  36   a  intersect each other in a substantially V-shape. The first inclined portion  32   a  and the second inclined portion  36   a  are formed such that the first thin portion  32   b  and the second thin portion  36   b  substantially overlap each other when viewed from the side surface side of the knuckle  20 . 
     In the present embodiment, the position of the through hole  40  for attaching a wheel speed sensor provided in the side surface portion of the body portion  22  is set so as to be in the vicinity of the first thin portion  32   b  and the second thin portion  36   b . 
     In this way, the first rib  32  and the third rib  36  are secured such that the ribs having a required height are relatively long by shortening the thin portions. As a result, a triangular structure is secured by the first rib  32 , the second rib  34 , and the third rib  36 , and the strength (rigidity) required in a normal state is maintained. 
     On the other hand, the first thin portion  32   b  and the second thin portion  36   b  serve as starting points of bending of the first rib  32  and the third rib  36 , respectively. When an external force is applied to the knuckle  20  from a front direction or an oblique front direction due to an inadvertent external force from the front direction or the oblique front direction, the first thin portion  32   b  and the second thin portion  36   b  serve as starting points of bending of the first rib  32  and the third rib  36 , respectively, the first rib  32  and the third rib  36  are bent, and the knuckle  20  is bent as a whole between the damper attachment portion  24  and the tie-rod attachment portion  26 . Thus, it is possible to reduce a possibility that the tie-rod attachment portion  26  enters the vehicle interior, and to suppress an influence on the vehicle interior. 
     By appropriately setting the length of the first inclined portion  32   a , that is, the position of the first thin portion  32   b , and the position of the second inclined portion  36   a , that is, the position of the second thin portion  36   b , a starting point of bending (fracture) can be controlled. 
     As described above, in the case where the position of the through hole  40  for attaching a wheel speed sensor provided in the side surface portion of the body portion  22  is set so as to be in the vicinity of the first thin portion  32   b  and the second thin portion  36   b , since the strength of the first thin portion  32   b  and the second thin portion  36   b  is further reduced, when an inadvertent force is applied from the outside, the knuckle  20  is easily bent at the portion, and the influence on the vehicle interior can be further suppressed.