Abstract:
A suspension system for a vehicle having a vehicle body and a road wheel includes a suspension corner connecting the road wheel to the vehicle body. The suspension corner maintains contact between the road wheel and a road surface. The suspension system includes a bladder arranged at the suspension corner for pumping a fluid in response to forces generated at the wheel and holding a volume of the fluid. The suspension system also includes a reservoir in fluid communication with the bladder for selectively accumulating the fluid pumped by and releasing the fluid to the bladder. The suspension system additionally includes a valve for selectively retaining the accumulated fluid in and releasing thereof from the reservoir. The height of the bladder varies in response to the volume of fluid being held by the bladder to set a ride height of the vehicle at the suspension corner.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a passively controlled adjustable ride height suspension for a vehicle. 
       BACKGROUND 
       [0002]    Contemporary on- and off-road going vehicles typically employ suspension systems that generally include a system of springs, shock absorbers, and linkages that connect a vehicle body to the vehicle&#39;s wheels. Because the majority of forces acting on the vehicle body are transmitted through contact patches between the road and the tires, one of the main objectives of a vehicle suspension is to maintain the contact between the vehicle&#39;s road wheels and the road surface. Additionally, the design of the suspension also influences the height of the vehicle body relative to the road surface. 
         [0003]    Vehicle suspension systems generally contribute to the vehicle&#39;s road-holding/handling and braking, as well as provide comfort and reasonable isolation from road noise, bumps, and vibrations to the vehicle occupants. Because these objectives are generally at odds, the tuning of suspensions involves finding a compromise that is appropriate to each vehicle&#39;s intended purpose. For example, a suspension for a sporting vehicle may be tuned to give up some ride comfort in return for enhanced operator control, while a suspension for a luxury vehicle may be tuned for the opposite outcome. 
       SUMMARY 
       [0004]    A suspension system for a vehicle having a vehicle body and a road wheel includes a suspension corner connecting the road wheel to the vehicle body. The suspension corner is configured to maintain contact between the road wheel and a road surface. The suspension system includes a bladder arranged at the suspension corner, characterized by a variable height, and configured to pump a fluid in response to forces generated at the wheel and hold a volume of the fluid. The suspension system also includes a reservoir in fluid communication with the bladder. The reservoir is configured to selectively accumulate the fluid pumped by the bladder and subsequently on demand release the fluid back into the hydraulic system that fluidly connects the reservoir to the bladder. The suspension system additionally includes a valve in fluid communication with the reservoir. The valve is configured to selectively retain the accumulated fluid in and release the accumulated fluid from the reservoir. The height of the bladder varies in response to the volume of the fluid being held by the bladder, i.e., is selectively inflated and deflated by the fluid, thereby setting a height of the vehicle body relative to the road surface, i.e., a ride height, at the suspension corner. 
         [0005]    The suspension system may additionally include a sensor configured to detect the volume of the fluid held by the bladder and generate a signal indicative of the volume. Furthermore, the suspension system may include a controller configured to receive the signal indicative of the volume of the fluid held by the bladder and regulate the valve to selectively accumulate and release the fluid by the reservoir. 
         [0006]    The suspension corner may include a control arm connecting the wheel to the vehicle body and a damper arranged between the control arm and the vehicle body. The damper used in the suspension corner is configured to cushion forces being generated at the wheel as the vehicle traverses the road surface. Furthermore, the forces generated at the wheel as the vehicle traverses the road surface may displace the control arm and in turn actuate the bladder to pump the fluid. 
         [0007]    The reservoir may be mounted to one of the vehicle body and the damper. 
         [0008]    The bladder may include a general ring shape defining a hollow middle section. Additionally, the damper may include a fastening member that extends through the middle section. 
         [0009]    The bladder may be arranged between the damper and the body and in such a case the fastening member is secured to the body. 
         [0010]    The bladder may be arranged between the damper and the control arm and in such a case the fastening member is secured to the control arm. 
         [0011]    The bladder may include a first bladder and a second bladder. In such a case the first bladder may be arranged between the damper and the body and the second bladder may be arranged between the damper and the control arm. 
         [0012]    The body may include a first pocket arranged to accept the first bladder and the control arm may include a second pocket arranged to accept the second bladder. 
         [0013]    The above features and advantages, and other features and advantages of the present disclosure, will be readily apparent from the following detailed description of the embodiment(s) and best mode(s) for carrying out the described invention when taken in connection with the accompanying drawings and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a plan view of a motor vehicle having a suspension system according to the disclosure. 
           [0015]      FIG. 2  is a schematic cross-sectional illustration of one type of a suspension corner of the vehicle shown in  FIG. 1  having a spring, a damper, a control arm, and an inflatable bladder in an inflated state, wherein the bladder is disposed between the damper and the control arm. 
           [0016]      FIG. 3  is a schematic illustration of the suspension corner shown in  FIG. 2 , wherein the bladder is shown in a deflated state. 
           [0017]      FIG. 4  is a schematic cross-sectional illustration of another type of suspension corner shown in  FIG. 1  having a strut, a control arm, and an inflatable bladder in an inflated state, wherein the bladder is disposed between the strut and the vehicle body. 
           [0018]      FIG. 5  is a schematic cross-sectional illustration of the suspension corner shown in  FIG. 4 , wherein the bladder is shown in a deflated state. 
           [0019]      FIG. 6  is a schematic perspective view of the bladder. 
           [0020]      FIG. 7  is a schematic illustration of the hydraulic circuit configured to control the suspension system. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Referring to the drawings, wherein like reference numbers refer to like components,  FIG. 1  shows a schematic view of a motor vehicle  10 , which includes a vehicle body  12 . The vehicle  10  also includes a powertrain  14  configured to propel the vehicle. As shown in  FIG. 1 , the powertrain  14  includes an engine  16  and a transmission  18 . The powertrain  14  may also include one or more motor/generators and a fuel cell, neither of which are shown, but a powertrain configuration employing such devices would be appreciated by those skilled in the art. 
         [0022]    The vehicle  10  also includes a plurality of road wheels that include front wheels  20  and rear wheels  22 . Although four wheels, i.e., a pair of front wheels  20  and a pair of rear wheels  22 , are shown in  FIG. 1 , a vehicle with fewer or greater number of wheels is also envisioned. As shown, a vehicle suspension system  24  operatively connects the body  12  to the front and rear wheels  20 ,  22  for maintaining contact between the wheels and a road surface  13 , and for maintaining handling of the vehicle. The suspension system  24  may include an upper control arm  26 , a lower control arm  28 , a shock absorber or damper  30 , and a spring  32  connected to each of the front and rear wheels  20 ,  22 . Although a specific configuration of the suspension system  24  is shown in  FIGS. 1-3 , other vehicle suspension designs are similarly envisioned, such as using a strut  34 , as represented by an individual suspension corner  36  shown in  FIGS. 4-5 ). 
         [0023]    The suspension system  24  also includes a plurality of knuckles  38 , each configured to support a respective road wheel  20 ,  22  via a wheel hub and bearing assembly (not shown).  FIGS. 2-3  depict the representative corner  36  of the suspension system  24 , which includes a representative knuckle  38 . Each knuckle  38  may be operatively connected to the body  12  via the upper control arm  26  and the lower control arm  28 , and have its motion in response to road input controlled by the combination of a shock absorber, a.k.a., damper  30  and spring  32 , or the strut  34 . The damper  30  or strut  34  is configured to cushion or dampen forces being generated at the wheel  20 ,  22  as the vehicle  10  traverses the road surface  13 . 
         [0024]    As shown in  FIGS. 2-6 , the suspension system  24  also includes a bladder  40  arranged at each suspension corner  36 . The bladder  40  constitutes a container that is finable by a fluid and configured to selectively expand in volume as additional fluid  44  is retained therein and contract as the fluid is removed therefrom. The bladder  40  is characterized by a variable height  42  (shown in  FIG. 6 ), wherein inflated height  42   a  is shown in  FIGS. 2 and 4 , and deflated height  42   b  is shown in  FIGS. 3 and 5 . The bladder  40  is positioned in line with the damper  30  or strut  34 . The bladder  40  is configured to pump a fluid  44  in response to forces and displacement  46  generated at the wheel  20 ,  22  as the vehicle  10  traverses the road surface  13  and the wheel moves vertically with respect to the road surface. At any time during operation of the vehicle  10 , the bladder  40  generally holds a volume of the fluid  44 . The volume of the fluid retained by the bladder  40  establishes an effective distance  47  between the lower control arm  28  and the vehicle body  12 . 
         [0025]    As shown in  FIG. 7 , the suspension system  24  additionally includes a reservoir  48  in fluid communication with the bladder  40  via a system of fluid tubes  50 . The reservoir  48  is configured to selectively accumulate the fluid  44  pumped by the bladder  40  and subsequently on demand release the fluid back into the fluid tubes  50 . A pump  52  is in fluid communication with the reservoir  48  via a fluid tube  50 . The pump  52  pressurizes the fluid  44  received from the reservoir  48  and delivers the pressurized fluid to an accumulator  54 . The accumulator  54  is controlled by a valve  56  to selectively retain the pressurized fluid  44  and when prompted to release the fluid to the bladder  40 . The valve  56  may be a one-way pressure valve that may be regulated by a controller that will be described in greater detail below. Accordingly, the height  42  of the bladder  40  is varied in response to the volume of the fluid  44  being supplied thereto from the accumulator  54  via the valve  56 . Furthermore, as the bladder  40  selectively inflates and deflates with the fluid  44 , the changing height  42  of each bladder sets a height of the vehicle body  12 , i.e.,  58 , relative to the road surface  13  at each suspension corner  36 . The height  42  of the bladder  40  may be varied by the valve  56  in discrete intervals or height steps, or varied substantially infinitely as deemed necessary. 
         [0026]    As shown in  FIGS. 4-5  and  7 , the suspension system  24  may also include a sensor  60  configured to detect the volume of the fluid  44  held by the bladder  40 , for example by sensing fluid pressure. The sensor  60  may also generate a signal indicative of the volume of the fluid  44  held by the bladder  40 . As additionally shown in  FIG. 1 , the vehicle  10  includes a controller  62  configured to receive the signal generated by the sensor  60 . Furthermore, the controller  62  regulates the valve  56  to selectively accumulate and release the fluid  44  retained by the accumulator  54 . The controller  62  may be a standalone control unit dedicated to regulating the valve  56  in order to vary the ride height  58  in response to road conditions, vehicle speed, and other pre-set variables, a vehicle body controller, or an integrated vehicle central processing unit. Such pre-set variables may be selected and then appropriate vehicle ride height  58  empirically established for each variable during testing and development of the vehicle  10  for subsequent programming into the controller  62 . 
         [0027]    As shown in  FIGS. 2-3 , the damper  30  may be arranged between the lower control arm  28  and the vehicle body  12 . Accordingly, the forces generated at the wheel  20 ,  22  displace the lower control arm  28  and in turn actuate and cycle the bladder  40  such that the volume of the fluid  44  contained within the bladder is pumped out. As shown in  FIG. 2 , the accumulator  54  may be mounted to the damper  30  or to the vehicle body  12  (as shown in  FIG. 3 ). In the case where the suspension corner  36  employs the strut  34 , the accumulator  54  may be similarly mounted to the strut (as shown in  FIG. 3 ) or to the vehicle body  12  (as shown in  FIG. 5 ). As shown in  FIG. 6 , the bladder  40  includes a general ring shape  40   a  defining a hollow middle section  40   b.  The damper  30  includes a fastening member  64  that extends through the middle section  40   b  and uses a complementary threaded nut  66  for retention of the damper to the vehicle  10 . 
         [0028]    As shown in  FIGS. 4-5 , in the case that the bladder  40  is arranged between the strut  34  and the vehicle body  12 , the fastening member  64  is secured via the threaded nut  66  to the vehicle body  12 , such as at the shock tower  68 . Although in  FIGS. 4-5  the bladder  40  is arranged between the strut  34  and the body  12 , as in the embodiment of  FIGS. 2-3 , the bladder may also be arranged between the damper  30  and the lower control arm  28 . As shown, the fastening member  64  extends through the lower control arm  28  and is then secured to the control arm via the threaded nut  66 . The suspension system  24  may also include more than one bladder  40  at each corner  36 . Each corner  36  may include one bladder  40  arranged between either the damper  30  or the strut  34  and the vehicle body  12 , and also include the second bladder  40  arranged between the damper or strut and the lower control arm  28 . Such twin-bladder configuration permits greater range in the variation of the ride height  58  for the vehicle  10 . As shown in  FIGS. 4-5 , the vehicle body  12  includes a first pocket  70  arranged to accept the first bladder  40  and, as shown in  FIGS. 2-3  the control arm includes a second pocket  72  arranged to accept the second bladder  40 . 
         [0029]    The controller  62  may be programmed to selectively regulate delivery of the fluid  44  into the first and/or second bladders  40  depending on the desired ride height  58  based on the road conditions, the speed of the vehicle  10 , and the general performance expected from the vehicle by its operator. Accordingly, the suspension system  24  provides a cost effective approach to regulating vehicle ride height by capturing kinetic energy generated by the suspension&#39;s articulated movement. Additionally, the suspension system  24  may facilitate reduction of fuel consumption of the vehicle  10  as a result of the reduced ride height that favorably impacts the vehicle&#39;s coefficient of air drag. Furthermore, the suspension system  24  achieves regulation of the vehicle ride height without resorting to the complexity of a full pneumatic suspension that generally eschews standard springs and dampers. 
         [0030]    The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims.