Abstract:
An air suspension system for a vehicle comprises four corner assemblies, wherein one corner assembly is located at a suspension position corresponding to each of the wheel corners for the vehicle. An air supply unit including a compressor, and an ECU are connected to the corner assemblies. The air supply unit is capable of independently adjusting the corner assemblies from one another. A sensor for measuring jounce/rebound travel for a wheel is associated with each of the corner assemblies and the air suspension system is operable adjust the air pressure at each of the four corner assemblies to provide optimized traction for the vehicle when at least one of the wheels has a predetermined amount of travel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This U.S. patent application claims the benefit of provisional patent application 62/263,176, filed Dec. 4, 2015, which is hereby incorporated by reference 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to automotive vehicles and more particularly to adjustable suspension systems for automotive vehicles. 
       BACKGROUND 
       [0003]    Suspension systems for automotive vehicles provide vehicle passengers with a more comfortable ride. Demand from vehicle owners for more controls and options has led to the development of adjustable air suspension systems. Depending on the current driving surface, different suspension operating modes may be selected by the vehicle operator. The suspension operating modes have present suspension parameters to provide the ideal suspension arrangement for various driving situations. Typical operating modes a driver may select include, a standard driving mode, a snow mode, an off-roading mode, etc. 
         [0004]    In addition to providing selected operating modes for various driving situations the suspension system may be adjusted when select operating conditions are met. For example, the vehicle height may be lowered when operating above a predetermined operating speed to obtain a better aerodynamic profile for the vehicle. Thus, adjustable air suspension systems provide a vehicle operator with a more efficient driving experience. 
         [0005]    Sport utility vehicles (SUV) and trucks can be used off road for rock climbing and other surfaces that are uneven compared to normal driving roads. Many off road enthusiasts are interested in the ramp travel index (RTI) or axle articulations of the vehicle. Ramp travel index rating is used to test and describe chassis limits of vehicles. A high axle articulation is good for off road performance on severe routes. Most stock SUVs have RTI measure values from 400-550. 
         [0006]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
       SUMMARY 
       [0007]    A method of adjusting an air suspension system for a vehicle comprises activating a traction optimization mode, and determining with an ECU an optimal pressure for each individual corner of the air suspension system to provide an optimal amount of traction for the vehicle. The ECU determines the manner to adjust each corner including to either increase or decrease pressure for each corner to achieve the optimal pressure at the corner based on a current pressure and controls the air supply in the determined manner to adjust the air spring pressures. The traction optimization mode is deactivated and the suspension system is adjusted to another mode by changing the air spring pressures. 
         [0008]    An air suspension system for a vehicle comprises four corner assemblies, wherein one corner assembly is located at a suspension position corresponding to each of the wheel corners for the vehicle. An air supply unit including a compressor, and an ECU are connected to the corner assemblies. The air supply unit is capable of independently adjusting the corner assemblies from one another. A sensor for measuring jounce/rebound travel for a wheel is associated with each of the corner assemblies and the air suspension system is operable adjust the air pressure at each of the four corner assemblies to provide optimized traction for the vehicle when at least one of the wheels has a predetermined amount of travel. 
         [0009]    Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and ap-pended claims with reference to the accompanying drawings, all of which form a part of this specification. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a schematic illustration of a vehicle having an air suspension system of the present invention; 
           [0012]      FIG. 2  is a schematic illustration of a frame for the vehicle having the air suspension system of  FIG. 1 ; 
           [0013]      FIG. 3  is a schematic illustration of the vehicle having the air suspension system of  FIGS. 1-2  illustrating example tire pressures for the vehicle tires; 
           [0014]      FIG. 4  is a schematic illustration of the vehicle having the air suspension system of  FIGS. 1-3  illustrating an example method of traction optimization. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements.  FIGS. 1 and 2  illustrate a vehicle, in this instance an SUV  10  having an air suspension system  12 . The air suspension system  12  is supported by a frame  14 . The air suspensions system has four corner assemblies  16 A-D located at each of the wheel  18  locations of the vehicle  10 . The four corner assemblies  16 A-D may be independently adjustable. Two corner assemblies  16 A, B are located at the front wheel  18 A, B corners of the vehicle  10  and two corner assemblies  16 C, D are located at the rear wheel  18 C, D corners of the vehicle. 
         [0016]    The air suspension system  12  includes an air supply unit  20  fluidly connected to the four corner assemblies  16 A-D. The air supply unit  20  includes an electronic control unit  22 , a compressor  24 , a reservoir  26  and a valve block  30 . The individual components of the air supply unit may be assembled together or supported on the vehicle at separate locations. In the embodiment shown the ECU  22  is located remote from the compressor  24 , reservoir  26  and valve block  30 . The individual components of the air supply unit  20  may be assembled together or supported on the vehicle  10  at separate locations. In the embodiment shown, the ECU  22  is located remote from the compressor  24 , reservoir  26  and valve block  30  (electrical connections not shown). Alternatively, the air suspensions system  12  may be an open loop system and the air supply unit may not include a reservoir  26 . 
         [0017]    The air supply unit  20  is connected to the four corner assemblies  16 A-D through the supply lines  28 . In the example shown, the air suspension system  12  is a closed system. The valve block  30  is controlled by the ECU  22  to regulate the air supply between the compressor  24 , the reservoir  26  and the four corner assemblies  16 A-D. The valve block  30  may be a single unit defining multiple valves, multiple valves located together, or multiple valves at different locations. Additionally, the reservoir  26  may be a single or multiple tank assembly. 
         [0018]    The four corner assemblies  16 A-D are adjustable to accommodate various driving conditions. Based upon the selected suspension mode the ECU  22  will regulate the air supply between the compressor  24 , reservoir  26  and the four corner assemblies  16 A-D to adjust the four corner assemblies  16 A-D from the current positions to the desired positions. When lowering any of the corner assemblies  16 A-D the excess air is sent to the reservoir  26  for storage. When raising any of the corner assemblies  16 A-D the required air is sent from the reservoir  26  to the appropriate corner assembly  16 A-D. The compressor  24  ensures that the air pressure within the system  12  is maintained at the desired level. Alternately, in the instance of an open system the excess air is released to the environment or pulled from the environment and pressurized as needed. The compressor  24  ensures that the air pressure within the system  12  is maintained at the desired level. 
         [0019]    The air suspension system  12  is adjusted at the direction of the vehicle operator by moving a selector, or when pre-determined operating conditions exist, e.g. the vehicle  10  accelerates above a certain speed and the suspension system  12  is lowered, when the vehicle  10  decelerates below a predetermined threshold the suspension system  12  raised. Therefore, the air suspension system  12  may be adjusted while the vehicle  10  is in motion. In this instance, the front corner assemblies  16 A, B may be adjustable together and the rear corner assemblies  16 C, D may be adjustable together. To provide the most aerodynamic adjustment possible, when the vehicle is travelling in a forward direction, the rear corner assemblies are adjusted to the new position first when the suspension system  12  is raised. However, when the suspension system  12  is lowered, the front corner assemblies  16 A, B are adjusted to the new position first. Alternately, each corner  16 A-D could be adjusted separately or all corners  116 A-D could be adjusted simultaneously. 
         [0020]      FIGS. 1-3  are schematic illustrations of a vehicle  10  with the air suspension system  12 .  FIG. 1  illustrates the vehicle where one wheel is elevated compare to the others. The air springs  16 A-D can be individually controlled to maintain as much contact with a tractive surface as possible. By sensing both the wheel travel and wheel load, the algorithm can adjust the pressure at each corner to optimize traction. The pressure at each corner can be either raised or lowered. Raising the pressure will move the vehicle downward in the rebound direction and lowering the pressure will move the wheel upward in the jounce direction. 
         [0021]    This mode could be enabled by the driver, or alternatively, could be activated automatically when certain pre-set conditions are met. However, this mode can only be activated when the vehicle is either stopped or moving very slowly, e.g. less than 3-5 mph. Adjusting, the air suspension pressure at the individual corners can be used in off road performance situations where there are large variations in the driving surface, to improve the Ramp Test Index (RTI) performance of a vehicle, and for improving traction for a vehicle that is stuck on uneven surfaces, e.g. a snow bank. 
         [0022]      FIG. 3  illustrates one example where the air suspension  12  of the current invention is used. The different pressures for the associated air spring are shown for situations where an individual corner is elevated compared to the other corners. The air spring pressure for the elevated wheel is deflated, as well as for the air spring at the diagonally opposing corner. The remaining two wheels, forming the opposing diagonal of the first two will have elevated air spring pressures, to help increase the clearance. 
         [0023]    Another example is shown in  FIG. 1  where RTI for a vehicle is calculated, one forward wheel is placed on a ramp, which is at a 15-30 degree angle. The vehicle is moved forward until one of the other three tries begins to leave the ground. The vehicle is then back down until all 3 tires are still o the ground. The distance travelled up the ramp is then measured and divided by the vehicle&#39;s wheelbase and multiplied by 1000 to give an RTI score, where b is the wheelbase for the vehicle, d is the distance travelled along the ramp, and r is the calculated RTI: 
         [0000]    
       
         
           
             r 
             = 
             
               
                 d 
                 b 
               
               × 
               1 
               , 
               000 
             
           
         
       
     
         [0024]    When the pressure in the air spring is controlled, as described in relation to  FIG. 3 , decreasing air spring pressure of the corner where wheel on the ramp and the diagonally opposite and increasing air spring pressure of the opposing diagonal corners the RTI rate increases as well, for example a 25% increase. 
         [0025]    Referring to  FIGS. 1-4  one embodiment of a method of adjusting an air suspension system is described, shown at  50 . The traction optimization mode is activated either individually or by meeting the preset conditions, shown at  52 . The ECU  22  compares the individual corners to determine the optimal pressure for each air spring corner  16 A-D, shown at  54 . The ECU  22  may receive data from the vehicle sensors (not shown) to detect these and other conditions including, but not limited to: wheel travel (jounce or rebound) at each corner, vehicle load at each corner, vehicle speed, etc. Based on this information the ECU  22  determines the optimal air spring pressure at each corner  16 A-D, shown at  56 . For each air spring  16 A-D the ECU  22  also determines the manner in which the air spring  16 A-D should be adjusted including if the pressure needs to be increased or decreased from the current pressure and the order in which the air spring corners  16 A-D should be adjusted, shown at  58 . For example, those needing an increase in pressure may be adjusted first, starting with the largest increase or simultaneously increased to the optional pressure. Then ECU  22  controls the air supply in the determined manner to adjust the air spring pressures, shown at  60 . The ECU  62  monitors the vehicle for predetermined conditions which will automatically cause the traction optimizer mode to end, shown as  62 . One way for the traction optimizer mode to terminate is if the vehicle  10  were to start travelling above a preset speed or if other present conditions were no longer met The traction optimizer mode can then be deactivated manually or automatically. The traction optimizer mode can then be deactivated manually or automatically. Whether automatic or manually the traction optimizer mode is deactivated, shown at  64  or can continue to operate and adjust air spring pressures using the traction optimization mode, shown at  66 . 
         [0026]    When the traction optimizer mode is ended the ECU  22  adjusts the suspension system to another mode by changing the air spring pressures accordingly, shown at  68 . The ending mode may be to the previous automatically selected mode, a new manually selected more, or a new automatically selected mode. 
         [0027]    While the best modes for carrying out the invention have been described in detail the true scope of the disclosure should not be so limited, since those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.